The Proposed Dredging of the Navigation Channel …...The Proposed Dredging of the Navigation Channel at Sligo Harbour Vol. 3: Natura Impact Statement, to inform Appropriate Assessment

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The Proposed Dredging of the Navigation Channel at Sligo HarbourVol. 3: Natura Impact Statement, to inform Appropriate Assessment

Sligo Harbour Dredging

Natura Impact Statement

An ecological impact assessment to support the Appropriate Assessment Process

Produced by

Aqua-Fact International Services Ltd

On behalf of

RPS Limited Issued October 2012

AQUA-FACT INTERNATIONAL SERVICES ltd12 KILKERRIN park TUAM rd GALWAY city www.aquafact.ie

[email protected] tel +353 (0) 91 756812 fax +353 (0) 91 756888

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Table of Contents

1. Introduction .............................................................................................. 1

1.1. The requirement for an assessment under Article 6 ............................... 11.2. The aim of this report .............................................................................. 21.3. Background – an overview of the Sligo Harbour Dredging project.......... 21.4. Consultation ............................................................................................ 31.4.1. Government Departments ............................................................................. 31.4.2. Other Bodies ................................................................................................. 31.5. Constraints.............................................................................................. 4

2. The Appropriate Assessment process .................................................. 5

2.1. Introduction ............................................................................................. 52.2. Stages .................................................................................................... 62.3. Alternatives ............................................................................................. 72.3.1. Introduction ................................................................................................... 72.3.2. Alternative dredging methods........................................................................ 82.3.3. Alternative timing of works ............................................................................ 82.3.4. Alternative dredge spoil disposal methods .................................................... 82.3.5. Alternative sea disposal sites ........................................................................ 9

3. The Ecological Impact Assessment ....................................................... 9

3.1. Introduction ............................................................................................. 93.1.1. Description of the project ............................................................................ 10

4. Natura 2000 sites ................................................................................... 11

4.1. Areas and Species of Scientific Interest – Sligo Harbour ...................... 124.1.1. Areas of Scientific Interest (ASI).................................................................. 134.1.1.1. Areas of Scientific Interest in County Sligo 1978 ...................................................... 14

4.1.1.2. Areas of Scientific Interest in County Sligo 1981 ...................................................... 14

4.1.2. Special Areas of Conservation (SAC) ......................................................... 154.1.3. Special Protection Area (SPA) .................................................................... 164.1.4. Natural Heritage Area (NHA)....................................................................... 164.1.5. Designations under the Wildlife Act, 1976 ................................................... 174.1.6. Proposed Nature Reserve in private ownership .......................................... 174.1.7. County Geological Sites .............................................................................. 174.1.8. International Reserves/Conventions............................................................ 174.2. Designated sites in the vicinity of the project ........................................ 184.2.1. Sligo Harbour .............................................................................................. 194.3. Characteristics of the designated sites ................................................. 204.3.1. Cummeen Strand/Drumcliff Bay SAC (Site code: 000627) .......................... 204.3.1.1. Conservation Objectives for Cummeen Strand SAC ................................................ 22

4.3.1.2. Other Annexed species present within the SAC ....................................................... 23

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4.3.2. Cummeen Strand SPA (Site code: 004035) ................................................ 244.3.2.1. Conservation Objectives Cummeen Strand SPA (Site code: 004035) ...................... 25

4.3.3. Lough Gill SAC (Site code: 001976)............................................................ 274.3.3.1. Conservation Objectives for Lough Gill SAC ............................................................ 29

4.3.3.2. Endangered fish species Lough Gill SAC................................................................. 30

4.4. Desk Study ........................................................................................... 314.4.1. Intertidal habitats......................................................................................... 314.4.1.1. Aquatic Services Unit, UCC – Dorrins Strand 2005 .................................................. 31

4.4.1.2. Aquatic Services Unit, UCC Intertidal Survey 2007 .................................................. 33

4.4.1.3. Aquatic Services Unit, UCC Intertidal Transect Survey 2007.................................... 34

4.4.1.3.1. Sligo Harbour Transect 1 ......................................................................................... 34

4.4.1.3.1.1. 20m from the shoreline – T1 high shore station........................................................ 36

4.4.1.3.1.2. 900m from the shoreline – T1, mid-shore station ..................................................... 36

4.4.1.3.1.3. 1950m from the shoreline – T1, low shore station .................................................... 36


4.4.1.3.2.1. 185m from the shoreline – T2, upper shore station .................................................. 37

4.4.1.3.2.2. 1460m from the shoreline – T2, mid-shore station ................................................... 37

4.4.1.3.2.3. 1990m from the shoreline – T2, low shore station .................................................... 37


4.4.1.3.3.1. 20m from the shoreline – T3, upper shore station .................................................... 38

4.4.1.3.3.2. 60m from the shoreline – T3, mid-shore station ....................................................... 38

4.4.1.3.3.3. 130m from the shoreline – T3, lower shore station ................................................... 38

4.4.1.4. BIOMAR and Office of Public Works intertidal surveys ............................................. 39

4.4.2. Subtidal habitats ......................................................................................... 414.4.2.1. BIOMAR and Office of Public Works subtidal surveys .............................................. 41

4.4.3. Birds ........................................................................................................... 414.4.3.1. Birds – Activities and threats ................................................................................... 43

4.4.3.2. Sligo Harbour - bird counts ...................................................................................... 44

4.4.3.3. Birdwatch Ireland Sligo Branch ................................................................................ 45

4.4.3.4. Drumcliff Bay Estuary .............................................................................................. 46

4.4.4. Marine Mammals ........................................................................................ 484.4.4.1. Whale and Dolphin Populations ............................................................................... 48

4.4.4.2. Seal populations...................................................................................................... 49

4.5. Field Survey – AQUAFACT 2010 ......................................................... 524.5.1. Intertidal survey 2010 .................................................................................. 524.5.1.1. Materials and Methods - 2010 ................................................................................. 53

4.5.1.2. Results 2010 ........................................................................................................... 53

4.5.1.2.1. Anthony Lynch - Clam site - Northern Walkover ....................................................... 53

4.5.1.2.2. Sligo Intertidal – navigation channel area................................................................. 63

4.5.2. Infaunal survey 2010 ................................................................................... 694.5.2.1. Sampling Procedure & Processing .......................................................................... 69

4.5.2.2. Data Processing ...................................................................................................... 71

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4.5.2.3. Results .................................................................................................................... 74

4.5.2.3.1. Fauna ..................................................................................................................... 74

4.5.2.3.1.1. UNIVARIATE ANALYSES ....................................................................................... 74

4.5.2.3.1.2. MULTIVARIATE ANALYSES ................................................................................... 76

4.5.2.3.2. Sediment................................................................................................................. 80

4.5.2.3.3. Organic carbon........................................................................................................ 83

5. Assessment of Likely Effects ............................................................... 84

5.1. Consideration of significance ................................................................ 845.2. Potential Impacts on Natura 2000 sites – Impacts Prediction ............... 865.2.1. Potential impacts on Cummeen Strand/Drumcliff Bay SAC ......................... 865.2.1.1. Potential impacts on habitats in Cummeen Strand/Drumcliff Bay SAC ..................... 86

5.2.1.1.1. Qualifying marine habitats for the Cummeen Strand/Drumcliff Bay SAC .................. 86

5.2.1.1.1.1. The removal of estuarine sediments ........................................................................ 87

5.2.1.1.1.2. Deposition of sediments on mudflats and sandflats .................................................. 87

5.2.1.2. Potential impacts on qualifying species and listed species for the Cummeen

Strand/Drumcliff Bay SAC ......................................................................................................... 87

5.2.1.2.1. Qualifying plant species for the SAC ........................................................................ 88

5.2.1.2.2. Listed bird species for the SAC – Annex I species (EU Birds Directive) .................... 88

5.2.1.2.3. Mammal species for the SAC – Annex II species (EU Habitats Directive) ................. 89

5.2.1.2.4. Qualifying Annex II and listed fish species for the SAC ............................................ 89

5.2.1.2.5. Annex (II and IV) species not listed as qualifying or of special interest for the SAC .. 89

5.2.1.2.5.1. Fish (Annex II) ......................................................................................................... 89

5.2.1.2.5.2. Otter (Lutra lutra) (Annex II and IV).......................................................................... 90

5.2.1.2.5.3. Marine mammals (Annex II and Annex IV) ............................................................... 91

5.2.1.3. Other fish species.................................................................................................... 91

5.2.2. Potential impacts on Cummeen Strand SPA ............................................... 925.2.2.1. Potential impacts on the SPA qualifying and listed bird species of interest ............... 92

5.2.2.2. Potential impacts on the macrobenthos - food source for SPA bird species.............. 94

5.2.2.3. Noise impact on benthos ......................................................................................... 95

5.2.2.4. Bivalve Beds ........................................................................................................... 95

5.2.2.5. Zostera Beds........................................................................................................... 97

5.2.3. Indirect Impacts on Natura sites in the wider locality, including Lough Gill SAC 995.2.4. Cumulative Impacts....................................................................................1005.2.4.1. Introduction ........................................................................................................... 100

5.2.4.2. Overall Cumulative Impact of All Projects .............................................................. 100

6. Mitigation measures ............................................................................ 105

6.1. Habitats in Cummeen Strand/Drumcliff Bay SAC ............................... 105

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6.1.1. The removal of estuarine sediments ..........................................................1056.1.2. Deposition of sediments on mudflats and sandflats ....................................1056.2. Species in the Cummeen Strand/Drumcliff Bay SAC.......................... 1066.2.1. Marine mammal species listed for the SAC – Annex II species (EU Habitats Directive) ................................................................................................................1066.2.2. Fish species (Annex II)...............................................................................1066.2.3. Otter (Lutra lutra) (Annex II and IV) ............................................................1066.2.4. Marine mammals (Annex II and Annex IV) .................................................1076.2.5. Other fish species ......................................................................................1076.3. Mitigation for Cummeen Strand SPA .................................................. 1076.3.1. Macrobenthos - food source for SPA bird species ......................................1076.3.1.1. Noise impact on benthos ....................................................................................... 108

6.3.1.2. Mussel Beds ......................................................................................................... 108

6.3.1.3. Zostera Beds......................................................................................................... 109

6.3.2. Indirect Impacts on Natura sites in the wider locality, including Lough Gill SAC 1096.4. QUALIFYING SPECIES AND LISTED SPECIES OF IMPORTANCE FOR THE SPA ............................................................................................. 109

7. Conclusions ......................................................................................... 110

7.1. Cummeen Strand/Drumcliff Bay SAC (Site code: 000627) ................. 1107.2. Cummeen Strand SPA (Site code: 004035) ....................................... 1107.3. Lough Gill SAC (Site code: 001976) ................................................... 111

8. Acknowledgements ................................................................................. 1

9. References ............................................................................................... 0

9.1. Additional information sources including web resources ........................ 5

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List of Figures

Figure 1: Overall layout of proposed dredging at Sligo Harbour & Natura 2000 Sites ..... 1Figure 2: Proposed dredging area for Sligo Harbour (red lines), 2010. .......................... 11Figure 3: Map showing protected sites in the Sligo Harbour area, (map source NPWS

website, October 2012). ............................................................................................. 13Figure 4: Map showing the location of the 30 intertidal stations surveyed by Aquatic

Services Unit, UCC in 2007........................................................................................ 34Figure 5: Figure showing locations of transects surveyed by ASU in Sligo Bay, 2007. 35Figure 6: Location map for the sites surveyed by BIOMAR and OPW teams in Sligo Bay

1996. ........................................................................................................................... 39Figure 7: Intertidal tyre tracks at Coney Island, Sligo Harbour (image screen grab taken

from www.bing.com/maps/ December 2010). ........................................................... 44Figure 8: Marine mammal sightings in the County Sligo area 2010-12. .......................... 48Figure 9: Map showing recent intertidal survey effort, Sligo Harbour. The route of the

current intertidal walkover is shown in red. Survey stations & transects carried out by ASU, Cork are also shown. Orthorectified images courtesy RPS Consulting Engineers Ltd. ............................................................................................................ 52

Figure 10: Location of observations made during the walkover survey, October 2010. 53Figure 11: Trestles, clam farm site, Sligo Harbour, 07th October 2010. .......................... 54Figure 12: Commercial clam park. South west Sligo Harbour, 07th October 2010.......... 55Figure 13: Mussel bed, Sligo beach, 07th October 2010. .................................................. 55Figure 14: Mussel bed, close view. A mix of blue mussel and clams. ............................ 56Figure 15: Algae (primarily fucoids) on mussel bank, Sligo Harbour, October 2010. .... 56Figure 16: Lugworm feeding casts, near mussel bank, Sligo harbour, October 2010. .. 57Figure 17: Seagrass and lugworm feeding casts, Sligo Harbour, October 2010. ........... 57Figure 18: Vaucheria sp. mat over intertidal muddy fine sand flat, Sligo Harbour, 07th

October 2010. ............................................................................................................. 58Figure 19: Gooses feeding on the intertidal sand flat, 07th October 2010. ...................... 59Figure 20: Fyke net on pole, Sligo Harbour, 07th October 2010 ....................................... 59Figure 21: Mussel bank, Sligo Harbour, 07th October 2010. ............................................ 60Figure 22: Mussel bank Sligo Harbour, 07th October 2010. ............................................. 60Figure 23: Commercial clam park (Noel Carter’s). Sligo Harbour, 07th October 2010 .... 61Figure 24: Clam cultivation hardware, Sligo Harbour, 07th October 2010. ...................... 62Figure 25: Rippled fine sand surrounding clam cultivation site, 07th October 2010....... 62Figure 26: Intertidal area with filamentous algal growth, Sligo Harbour, October 2010. 63Figure 27: Points of interest near the navigation channel walkover area 07th October

2010. ........................................................................................................................... 64Figure 28: Rippled fine sand with some algae, 08th October 2010. ................................. 65Figure 29: Channel marker, Sligo harbour, 08th October 2010. ....................................... 65

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Figure 30: Base of channel marker & training wall, Sligo harbour, 08th October 2010. .. 66Figure 31: Intertidal sand flat, Sligo Harbour, 08th October 2010. ................................... 66Figure 32: View towards Sligo along navigation channel, 08th October 2010. ................ 67Figure 33: Encrusting flora and fauna on the northern Sligo harbour navigation channel

training wall, Sligo Harbour, 08th October 2010. ....................................................... 68Figure 34: Muddy sand flat adjacent to training wall, Sligo harbour approach channel,

08th October 2010. ...................................................................................................... 68Figure 35: Map showing subtidal sampling locations ..................................................... 70Figure 36: Dendrogram showing the natural grouping of each station sampled in Sligo

Harbour. ..................................................................................................................... 78Figure 37: MDS ordination showing the natural grouping of each station sampled in

Sligo Harbour. ............................................................................................................ 79Figure 38: Sediment grain size data ................................................................................. 82Figure 39: Sediment type according to Folk (1954) ......................................................... 82

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List of Tables

Table 4-1: Natura sites within 15km of the proposed works ........................................... 18Table 4-2: Other designated sites within 15km of the proposed works .......................... 19Table 4-3: Annex I habitats listed on the Natura 2000 Standard Data Form ................... 21Table 4-4: Species present covered by Article 4 of the Directive 70/409/EEC (the Birds

Directive) and Annex II of Directive 92/43/EEC (the Habitats Directive) – from the Natura 2000 Standard Data Form .............................................................................. 21

Table 4-5: Other species of Flora and Fauna of importance – from the Natura 2000 Standard Data Form................................................................................................... 22

Table 4-6: Annexed species present within the Natura site but which are not listed on the Natura 2000 Standard Data Form or on the Conservation Objectives for the Site. ............................................................................................................................ 23

Table 4-7: Species present covered by Article 4 of the Directive 70/409/EEC (the Birds Directive) – from the Natura 2000 Standard Data Form ........................................... 25


Table 4-9: Annex I habitats listed on the Natura 2000 Standard Data Form ................... 28Table 4-10: Species present covered by Article 4 of the Directive 70/409/EEC (the Birds

Directive) and Annex II of Directive 92/43/EEC (the Habitats Directive) – from the Natura 2000 Standard Data Form .............................................................................. 28


Table 4-12: Subtidal station co-ordinates. ....................................................................... 70Table 4-13: The classification of sediment particle size ranges into size classes

(adapted from Buchanan, 1984) ................................................................................ 70Table 4-14: Diversity indices for the 15 stations sampled in Sligo Harbour. .................. 76Table 4-15: SIMPER Results ............................................................................................. 79Table 4-16: Granulometry results for the 16 stations sampled in Sligo Harbour (as

percentage weight of the total sample). ................................................................... 81Table 4-17: Sediment granulometry and organic carbon results for the fourteen stations

surveyed off Sligo, 06th October, 2010. ..................................................................... 83Table 5-1: Summary of critical thresholds for mussel (Mytilus edulis) beds. ................ 98Table 5-2: Tolerance thresholds of Zostera spp. to turbidity levels................................ 99Table 5-3: Tolerance thresholds for Zostera spp. to sedimentation. ............................ 100Table 5-4: Summary of expected impacts on marine habitats and species in the Natura

sites .......................................................................................................................... 103

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Appendix A – BIOMAR project data tables – Intertidal and subtidal sites near Sligo Harbour

Appendix B – SAC site synopsis

Appendix C – Benthic Fauna Species List, AQUAFACT fieldwork 2010

Appendix D – Irish Whale and Dolphin Group sightings tables – Sligo area

Appendix E – Ecological site evaluation criteria (derived from NRA and IEEM EcIA guidelines)

Appendix F – Hydrodynamic Modelling Chapter of Environmental Appraisal Report

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1. Introduction

1.1. The requirement for an assessment under Article 6

The requirement for appropriate assessment is set out in the EU Habitats Directive

(92/43 EEC) in Article 6.3 which states:

‘any plan or project not directly connected with or necessary to the management of

the site but likely to have a significant effect thereon, either individually or in

combination with other plans or projects, shall be subject to appropriate assessment

of its implications for the site in view of the site's conservation objectives’.

Figure 1: Overall layout of proposed dredging at Sligo Harbour & Natura 2000 Sites

© Ordnance Survey Ireland. All rights reserved. Licence number 2010/20 CCMA/ Sligo County Council

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1.2. The aim of this report

This Natura Impact Statement (NIS) has been prepared in accordance with the

current guidance (NPWS, 2009, Revised February 2010), and provides an ecological

impact assessment (EcIA) for the proposed capital and maintenance dredging of the

Sligo Harbour navigation channel.

The NIS provides the information required in order to establish whether or not the

proposed development is likely to have a significant impact on the Natura sites in the

context of their conservation objectives and specifically on the habitats and species

for which the Natura 2000 conservation sites have been designated. In the case of

the proposed development, the Natura 2000 sites are:

Cummeen Strand/Drumcliff Bay Special Area of Conservation (SAC Site

Code 000627)

Cummeen Strand SPA (SPA Site Code 004035)

Lough Gill SAC (SAC Site Code 001976).

By taking the ecological impact assessment in a step by step manner in relation to

the habitats and species of these three Natura sites, together with their conservation

objectives, this report seeks to inform the screening process required as the first

stage of the process pursuant to Article 6.3 of the EU Habitats Directive and also to

provide full and detailed information as required for the second, that of Appropriate

Assessment should the competent authority decide that such an assessment is

required. This Natura Impact Statement has been undertaken by the following

ecological experts:

AQUAFACT International Services Ltd.

Natura Environmental Consultants

1.3. Background – an overview of the Sligo Harbour Dredging project

RPS have been commissioned by Sligo County Council to examine the feasibility of

carrying out maintenance and capital dredging in Sligo Harbour (see Figure 1). In

order to make informed applications for statutory consents (Foreshore Licence and

Dumping at Sea Licence), AQUAFACT and Natura have been tasked with examining

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and describing the intertidal and subtidal flora and fauna that exists in Sligo Harbour

and investigating the potential impact of the proposed work on the habitats and

species present.

1.4. Consultation

1.4.1. Government Departments

Initial consultations with the National Parks and Wildlife Service (NPWS) of the

Department of Arts, Heritage and the Gaeltacht1 in relation to the proposed Sligo

Harbour dredging commenced in September of 2009 and are ongoing.

Consultations have also taken place with:

The Local Authority (Sligo County Council),

The Department of Communications, Energy and Natural Resources,

The Department of Education and Skills

The Department of Foreign Affairs and Trade

The Department of Finance

The Department of Transport, Tourism and Sport

The Department of Health

The Department of Agriculture, Food and the Marine2

the Foreshore Unit of the Department of Environment Community and local

Government, and with their technical advisers including the Marine Institute.

1.4.2. Other Bodies

Other bodies consulted are as follows:

Environmental Protection Agency

An Taisce the National Trust for Ireland

Birdwatch Ireland

Blue Flag beaches

Inland Fisheries Ireland

1

Formerly part of the Department of Environment, Heritage and Local Government, which became the Department of Environment Community and local Government in 2011. Heritage functions were transferred to the Department of Arts, Heritage and the Gaeltacht. 2

Formerly the Department of Agriculture, Fisheries and Food

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Coastwatch

Coillte

Commissioners of Irish Lights

Donegal Bay Sea Angling Club

Eircom

Electricity Supply Board

Fáilte Ireland North West

Federation of Irish Fishermen

Geological survey of Ireland

Health and Safety Authority

Office of Public Works (Heritage Ireland)

Iarnród Éireann

Irish Federation of Sea Anglers

Irish Whale and Dolphin Group

National Roads Authority

Royal National Lifeboat Institution

Sligo Harbour Commissioners

1.5. Constraints

The main constraints are:

The fact that the proposed dredging operations are to be carried out within a

SAC and SPA with the potential for impacting on that SAC/SPA and indirectly

on three species inhabiting a neighbouring SAC

The need to locate a suitable disposal site for the resulting dredge spoil that

will be acceptable to conservation and fishing concerns

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2. The Appropriate Assessment process

2.1. Introduction

There is a requirement, under Article 6(3) of the EU Habitats Directive (Directive

92/43/EEC), to carry out an Appropriate Assessment. The first step of the

Appropriate Assessment process is to establish whether, in relation to a particular

plan or project, Appropriate Assessment is required. Article 6(3) states:

‘Any plan or project not directly connected with or necessary to the management of

the site but likely to have a significant effect thereon, either individually or in

combination with other plans or projects, shall be subject to appropriate assessment

of its implications for the site in view of the site’s conservation objectives. In the light

of the conclusions of the assessment of the implications for the site and subject to

the provisions of paragraph 4, the competent national authorities shall agree to the

plan or project only after having ascertained that it will not adversely affect the

integrity of the site concerned and, if appropriate, after having obtained the opinion of

the general public.’

A number of guidance documents on the appropriate assessment process have been

referred to during the preparation of this NIS. These are:

Appropriate Assessment of Plans and Projects in Ireland - Guidance for

Planning Authorities (NPWS 2009, Revised February 2010);

EU Guidance document on Article 6(4) of the 'Habitats Directive' 92/43/EEC

(2007);

Assessment of plans and projects significantly affecting Natura 2000 sites.

Methodological guidance on the provisions of Article 6(3) and (4) of the

Habitats Directive 92/43/EEC (Nov. 2001 – published 2002); and

Managing Natura 2000 Sites: The provisions of Article 6 of the ‘Habitats’

Directive 92/43/EEC (2000).

Should a decision be reached to the effect that it cannot be said with sufficient

certainty that the development will not have any significant effect on the Natura 2000

sites, then, as stated above, it is necessary and appropriate to carry out an

appropriate assessment of the implications of the development for the sites in view of

their conservation objectives.

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The guidance for Appropriate Assessment (NPWS, 2009, revised February 2010)

states:

“AA is an impact assessment process that fits within the decision-making framework

and tests of Articles 6(3) and 6(4) and, for the purposes of this guidance, it comprises

two main elements. Firstly a Natura Impact Statement – i.e. a statement of the likely

and possible impacts of the plan or project on a Natura 2000 site (abbreviated in the

following guidance to “NIS”) must be prepared. This comprises a comprehensive

ecological impact assessment of a plan or project; it examines the direct and indirect

impacts that the plan or project might have on its own or in combination with other

plans and projects, on one or more Natura 2000 sites in view of the sites’

conservation objectives. Secondly, the competent authority carries out the AA, based

on the NIS and any other information it may consider necessary. The AA process

encompasses all of the processes covered by Article 6(3) of the Habitats Directive,

i.e. the screening process, the NIS, the AA by the competent authority, and the

record of decisions made by the competent authority at each stage of the process, up

to the point at which Article 6(4) may come into play following a determination that a

plan or project may adversely affect the integrity of a Natura 2000 site”.

2.2. Stages

The European Commission’s guidance promotes a four stage process (see Box 1

below) to complete the Appropriate Assessment, and outlines the tests required at

each stage. Stages 1 and 2 deal with the main requirements for assessment under

Article 6.3 Stage 3 may be part of Article 6(3) or a necessary precursor for Stage 4.

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This NIS includes the ecological impact assessment and testing required under the

provisions of Article 6(3) by means of the first stage of Appropriate Assessment, the

screening process (as set out in the EU Guidance documents). EU guidance3 states:

“This stage examines the likely effects of a project or plan, either alone or in

combination with other projects or plans, upon a Natura 2000 site and considers

whether it can be objectively concluded that these effects will not be significant. This

assessment comprises four steps:

1) determining whether the project or plan is directly connected with or

necessary to the management of the site;

2) describing the project or plan and the description and characterisation of

other projects or plans that in combination have the potential for having

significant effects on the Natura 2000 site;

3) identifying the potential effects on the Natura 2000 site;

4) assessing the significance of any effects on the Natura 2000 site”.

The NIS also provides the information required for the Competent Authority to

complete the Appropriate Assessment (Stage 2) should this be necessary and

appropriate in the opinion of the Competent Authority. An evaluation of alternatives

has also been provided to demonstrate that all feasible alternatives for the proposed

development have been considered and that the option with the least ecological

impact has been selected.

2.3. Alternatives

2.3.1. Introduction

The consideration of alternatives is examined in detail in Attachment B.1 of the

dumping at sea licence application. A Feasibility Study was undertaken by RPS

2010 (RPS, 2010), which examined the various options for disposing of or reusing

the dredged material from this scheme. The broad conclusions of the Feasibility

Study are summarised below: 3 Paragraph 3.1 of ‘Assessment of plans and projects significantly affecting Natura 2000 sites. Methodological

Guidance on the provisions of Article 6(3) and (4) of the Habitats Directive 92/43/EEC’ (Nov. 2001)

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2.3.2. Alternative dredging methods

Due to the relatively small proposed dredging volumes the scheme is likely to be

undertaken by a small scale local dredging company. The specific type of dredger

which will undertake the work will therefore not be known until a contractor has been

appointed. There are two types of dredger which could undertake the main bulk of

the work in removing the 250,000m³; a suction dredger or a backhoe dredger. A

water injection dredger is proposed for maintenance dredging of circa 5,500m³ of

sediments in the immediate vicinity of the Deepwater and Barytes Jetties.

2.3.3. Alternative timing of works

Owing to the distance offshore of the proposed dump site, the timing of the

conventional dredging works will largely be influenced by the availability of a suitable

weather window. Specifying an explicit timeframe in which dredging works must take

place would be likely to add significant cost to the project and would be undesirable

to the applicant; unless there are significant environmental impacts predicted which

can only be mitigated against by an adjustment to the timing of the works.

2.3.4. Alternative dredge spoil disposal methods

RPS have undertaken a detailed review of the alternatives to dumping at sea for the

disposal of the dredged sediment in a Feasibility Study prepared in 2010. The

following alternatives to disposal of the dredged material at an offshore dump site

were examined in detail, alongside the “do nothing” option:

Beneficial reuse for future building projects

Disposal on land

Reclamation of land within Sligo Harbour

Incineration

Disposal at licensed offshore dumping at sea site

The conclusion of the feasibility report was that there is no feasible alternative means

of disposal of the dredged material other than the disposal at a licensed dumping site

at sea. Chemical sediment analysis of the dredged material has been completed and

the Marine Institute has confirmed that the material is suitable for disposal at sea

under the terms of the Dumping at Sea Act, 1996 (as amended), provided a suitable

offshore location can be identified and a dumping at sea licence granted for its use.

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2.3.5. Alternative sea disposal sites

Further to the first round of consultation, the Killybegs Fishermen’s Organisation

(KFO) confirmed that the originally proposed offshore dump site location, sited circa

15 Nautical Miles from Sligo Harbour, comprised an important fish spawning ground.

RPS subsequently took on board a number of comments from both the statutory

consultees and key fishery interest groups in selecting a suitable alternative location

for the dump site. A new disposal site some 34 Nautical Miles from Sligo Harbour in

water depths circa 93m was chosen. Although it does not fully meet all the criteria

specified by the KFO, as water depths in excess of 100m were requested, this is the

furthest distance from Sligo which can enable the dredging works to proceed on each

rising tide. The 100 metre contour as surveyed by the INFOMAR project is some 43

nautical miles (80km) from Sligo Port, beyond the reach of a small dredger and is

documented in the Marine Institute Atlas of Commercial Fisheries around Ireland

2009 (2010) as an important area for commercial fishing of demersal species.

Any further offshore would effectively double the cost of the scheme and render it

uneconomic. Current metering studies including the deployment of current

measurement drogues at spring and neap tides have identified that tidal currents

present at the site are relatively low and that residual currents will not transport the

dumped sediment back into Donegal Bay.

3. The Ecological Impact Assessment

3.1. Introduction

The approach and methodology to the Ecological Impact Assessment for this Natura

Impact Statement has been undertaken with due regard to the EPA Advice Notes on

Current Practice (2003); EPA ‘Guidelines on the Information to be contained in

Environmental Impact Statements’ (2002); and the Institute of Ecology and

Environmental Management’s ‘Guidelines for Ecological Impact Assessment’ (IEEM,

2006) and with reference to the National Roads Authority (NRA) ‘Guidelines for

Ecological Impact Assessment’ (Revision 2, 2009).

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The ecological characteristics of the Natura 2000 sites are described in Section 4 of

this statement, followed by Assessment of Likely Effects, Mitigation and Residual

impacts in Sections 5, 6 and 7 respectively. Conclusions are set out in section 8.

The relevant sections of the Appraisal Report (Chapter 6, “Birds” and Chapter

5,”Intertidal and Subtidal Flora & Fauna and Marine Mammals”, may be referred to

for further detail on species and habitats.

A summary description of the Project is provided below at 3.1.1.

3.1.1. Description of the project

In order to make Sligo Port viable as a working commercial port, Sligo County

Council are proposing to carry out dredging works within the harbour and approach

channel. A dredging scheme was previously carried out in 1984 which created a

dredged depth of -2.5m CD within the navigation channel. Subsequent large scale

maintenance dredging was also carried out in the channel during 1998.

At present, the area immediately downstream of the Deepwater Jetty has only a

narrow channel (see bathymetric survey shown on Drawing 3) c. 4 metres wide in

which depths achieve -2.0mCD. It is proposed to clear this small section of the

approach channel back to c. 35m in breadth and also to remove small pockets of

siltation immediately in front of the berths by water injection dredging in the

immediate short term. This is the minimum amount of dredging required to maintain

operations at the berths.

In order to enable vessels of between 3,500 and 4,000 DWT with a draught of up to

5.9m to enter the Harbour in a window either side of High Water during Spring and

Neap Tides, it is proposed to dredge to a depth of -3.0 m CD. This scheme

represents the minimum works required in order to support a viable port. The

dredging will take place within the main navigation channel, adjacent to training walls

and also along short stretches between the end of training wall and Oyster Island.

The volume of dredged material arising from the dredging operations will be in the

order of approximately 250,000 m3 of fine silty sand.

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Figure 2: Proposed dredging area for Sligo Harbour (red lines), 2010.

It is proposed that the resulting dredge spoil material will be disposed of at a licensed

offshore dump site. A dumping at sea licence, required for the disposal, is therefore

being applied for. Water injection dredging also requires a dumping at sea permit

even though it does not have a defined “dump site”.

4. Natura 2000 sites

The Natura 2000 sites that will be directly affected by the proposed dredging works

are:

Cummeen Strand/Drumcliff Bay SAC (Site Code: 000627)

Cummeen Strand SPA (Site Code: 004035)

A further Natura 2000 site that may be indirectly affected by the proposed dredging

works is:

Lough Gill SAC (Site Code: 001976)

Extract from Admiralty Chart 2852 © Crown copyright UKHO. Not for Navigation Use

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There follows a short resumé of the history of designations and legislation which

currently applies to sites and species in Ireland and is given in order to put the

current conservation status of coastal habitats in the Sligo area into perspective

(source http://www.heritagecouncil.ie/publications; NPWS, 2010). It should be noted

that the situation regarding SAC designation is inevitably in a state of flux due to the

nature of the whole process of identifying potential sites, creation of new SACs,

deletion of part (or all) of some sites and amalgamation of others. Further information

about particular sites, including detailed site descriptions may be found on the

National Parks and Wildlife Service’s website.

Subsection 4.4 of this Section details the results of the desk study and field survey

tasks carried out by AQUAFACT International Service Ltd and Natura Environmental

Consultants.

4.1. Areas and Species of Scientific Interest – Sligo Harbour

Figure 3 overleaf shows an overview of sites currently protected in the Sligo area.

This map was produced using the National Parks and Wildlife Service online Maps

and Data service (accessed October 2012). It shows the locations of Special

Protection Areas (SPAs), Natural Heritage Areas and Proposed Natural Heritage

Areas (NHAs & pNHAs) and Special Areas of Conservation.

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Figure 3: Map showing protected sites in the Sligo Harbour area, (map source NPWS website, October 2012).

4.1.1. Areas of Scientific Interest (ASI)

In 1971 a unit, the Conservation and Amenity Advisory Service, was established

within An Foras Forbartha to provide specialist advice to the planning sections of

Local Authorities. A number of reports were produced by this unit that were based on

data abstracted from the files of the Conservation Unit of An Foras Forbartha, from

published literature and from several periods of field observations in November, 1972

- January, 1972. The subject of a series of these reports was the description and

mapping of Areas of Scientific Interest (ASIs) in Ireland. An ASI was defined as ‘a

site with natural or semi-natural features of ecology, geology or land-form. It may be

valuable for supporting communities or populations of characteristic or endangered

plants and animals, useful in describing the process or factors that govern their

appearance or important in interpreting the structure of land and its origins’ (An Foras

Forbartha, 1981). Goodwillie (1972) produced the first preliminary list of ASIs for

County Sligo. The importance of each area detailed was assigned to one of four

importance categories:

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International

National

Regional

Local

A priority rating of A, B or C – a measure of the relative urgency necessary for

protection of an ASI – was also assigned to each area. This priority rating was based

on a combination of the following:

The importance of the area (as categorised above)

The vulnerability of the area

The nature and imminence of any threats to the area

Ballysodare Bay was the largest site identified for Scientific Interest (3890 acres or

ca. 1611 hectares for ornithological and botanical reasons). Smaller coastal sites

included:

Streedagh Point

Serpent Rock

Aughris Head

Mullagh Mór

Derinch Island

Iniscrone Spit

Strandhill Dunes

Deadman’s Point (Rosses Point) and

Yellow Strand (Raghly).

4.1.1.1. Areas of Scientific Interest in County Sligo 1978

A second preliminary heritage inventory report detailing ASIs in County Sligo was

published in 1978 (Curtis et al., 1978). As was the case for the 1972 report,

Ballysodare Bay was still included as the largest coastal site (ca. 1550 hectares). In

addition, this report detailed a similar list of smaller coastal sites.

4.1.1.2. Areas of Scientific Interest in County Sligo 1981

A National Heritage Inventory Report detailing Irish ASIs was published by An Foras

Forbartha in 1981. This made available to the public and other interested parties a

summary of the information contained in the county reports. The information

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contained in this report acted as a baseline against which future changes in the

quality or importance of sites could be measured. Cummeen Strand (700 hectares of

mudflat habitat) was listed as an ASI for the first time in this report. It was listed as a

site of National Importance. The description of the site was as follows:

‘An internationally important flock of brent geese (2,250) pause on mudflats to feed in

October, when widgeon (2,000) are also present. About 200 geese remain through

the winter, moving between Cummeen and Ballysodare Bay. The area is the richest

site for waders in the county, especially for oystercatcher (700).’

Ballysodare Bay (1500 hectares of mudflats and saltmarsh) was listed as a site of

Regional Importance, again primarily due to its importance to birdlife. The process of

identification and description of the sites detailed in this report were the first steps in

Ireland’s contribution towards the current EU wide network of protected sites –

Natura 2000. Natura 2000 is comprised of Special Areas of Conservation (SAC)

designated by Member States under the Habitats Directive, and also incorporates

Special Protection Areas (SPAs) which they designate under the 1979 Birds

Directive. Many of the original ASIs are now incorporated into various parts of the

Natura 2000 network.

4.1.2. Special Areas of Conservation (SAC)

These sites are protected under legislation from significant damage to their relevant

habitats and species on a European as well as a National level. Special Areas of

Conservation (SACs) are designated under Article 3 of the Habitats Directive

92/43/EEC of 21 May 1992 on the conservation of natural habitats and of wild fauna

and flora, as part of the Natura 2000 network (Transposed into Irish law by the

Natural Habitats Regulations 1996. (S.I. No 94 0f 1997). This network comprises

Annex I habitats - "natural habitat types of community interest whose conservation

requires the designation of Special Areas of Conservation" and the habitats of Annex

II species - "animal and plant species of community interest whose conservation

requires the designation of Special Areas of Conservation". In addition, the directive

states that: "The Natura 2000 network shall include the special protection areas

classified by the Member States pursuant to Directive 79/409/EEC". Special Areas of

Conservation will be referred to as SACs hereafter for simplicity. SAC sites in close

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proximity to the proposed dredging works are given along with Special Protection

Areas (SPAs) in Table 4-1.

4.1.3. Special Protection Area (SPA)

These sites are protected under the legislation from actions that would damage their

value to bird species, especially those on Annexe 1 of the Directive. Special

Protection Areas (SPAs) are designated under Directive 79/409/EEC of 2 April 1979

on the conservation of wild birds (the Birds Directive). This was transposed into Irish

law by the Conservation of Wild Birds Regulations (S.I. 291 of 1985). Under the

Directive Ireland is obliged to protect the habitats of birds which are vulnerable to

habitat change or due to their low population numbers i.e. rarity. Aspects of habitat

protection are in the context of pollution, deterioration of habitat and disturbance.

This directive is implemented in Ireland under Statutory Instrument (1985). Coastal

SPAs in close proximity to the proposed works are listed in Table 4-1.

4.1.4. Natural Heritage Area (NHA)

This designation, established following the review survey of Areas of Scientific

Interest (ASI), forms the basic site network for habitat conservation. This is an area

considered important for the habitats present or which holds species of plants and

animals whose habitat needs protection. To date, 75 raised bogs have been given

legal protection, covering some 23,000 hectares. These raised bogs are located

mainly in the midlands. A further 73 blanket bogs, covering 37,000ha, mostly in

western areas are also designated as NHAs. All three designated NHA sites in

County Sligo are bogs.

In addition, there are 630 proposed NHAs (pNHAs), which were published on a non-

statutory basis in 1995, but have not since been statutorily proposed or designated

(www.npws.ie, 2010). These sites are of significance for wildlife and habitats. Some

of the pNHAs are tiny, such as a roosting place for rare bats. Others are large - a

woodland or a lake, for example. The pNHAs cover approximately 65,000ha and

designation will proceed on a phased basis over the coming years.

Prior to statutory designation, pNHAs are subject to limited protection, in the form of:

Rural Environment Protection Scheme (REPS) plans which require

conservation of pNHAs and operate for a period of 5 years

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Forest Service requirement for NPWS approval before they will pay

afforestation grants on pNHA lands

Recognition of the ecological value of pNHAs by Planning and Licensing

Authorities. Under the Wildlife Act 1976 as amended by the Wildlife

(Amendment) Act 2000, NHAs are legally protected from damage from the

date they are formally proposed for designation.

4.1.5. Designations under the Wildlife Act, 1976

Section 15 Wildlife Act, 1976 (amended by the Wildlife Amendment Act 2000)

designates Nature Reserves in the ownership of the Minister for Environment

Heritage and Local Government. Statutory Nature Reserves, of which there are 78

nationally (1 in County Sligo – Ballygilgan (Lissadell) Nature Reserve – that has a

coastal element on the shore of Drumcliff Bay), and Wildfowl Sanctuaries of which

there are 68 nationally (2 in County Sligo) fall under the protection afforded by this

legislation. Areas where the specific protection of one or more species of animal is

required may be designated as a Refuge for Fauna under this legislation (seven of

these exist in Ireland – they are mainly islands or cliff faces).

4.1.6. Proposed Nature Reserve in private ownership

Section 16 of the Wildlife Act, 1976 (amended by the Wildlife Amendment Act 2000)

designates Nature Reserves in private ownership.

4.1.7. County Geological Sites

County geological sites have no statutory protection but are considered within the

planning system. The geological Survey of Ireland (GSI) has suggested the

protection of a series of scientifically interesting coastal rock features in County Sligo.

GSI also promote the protection of historic and archaeological mining heritage.

Several of these sites were listed as ASIs and are also contained within the current

network of SACs.

4.1.8. International Reserves/Conventions

Wetland Sites of International Importance - Ramsar Convention

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Ratified by Ireland in 1984, the Convention on Wetlands came into force in 1985. Of

a total of 45 sites designated as Wetlands of International Importance only one site in

Sligo is of direct relevance to the proposed dredging work:

Cummeen Strand (Ramsar site No. 842). Area: 1,491 ha; 54º17’N 008º30’W.

Special Protection Area EC Directive. An estuarine arm of Sligo bay, made

famous by poet W. B. Yeats, with mudflats and sandflats. Important arrival

point for Brent geese Branta bernicla and also has internationally important

numbers of Ringed Plover Charadrius hiaticula.

Neither UNESCO Biosphere Reserves (two sites in Ireland) nor Council of Europe

Biogenetic Reserves (14 sites in Ireland) are applicable to the Sligo area.

4.2. Designated sites in the vicinity of the project

There are a number of designated sites within 15km of the proposed development.

Natura 2000 sites are listed in Table 4-1, while others including proposed Natural

Heritage Areas (NHAs) are listed in Table 4-2.

Table 4-1: Natura sites within 15km of the proposed works

Designation Site Name Site Code

Distance from the proposed development (approximate)

Special Area of

Conservation (SAC)

Cummeen Strand/Drumcliff

Bay 000627 0km

Lough Gill SAC 001976 2km

Ballysadare Bay 000622 5km

Special Protection Area

Cummeen Strand 004035 0km


Drumcliff Bay 004013 2km

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Table 4-2: Other designated sites within 15km of the proposed works

Designation Site Name Site Code Distance from the proposed development

Natural Heritage Areas

(NHA)

Cummeen strand/Drumcliff

Bay 000627 0km


Ramsar Sites Cummeen Strand 7IE034 0km

4.2.1. Sligo Harbour

Sligo Harbour is a large embayment located between Sligo City to the east and

Rosses Point village to the west. It measures approximately 6 km in length (from

West to East) and is approximately 3 km wide at its widest point. It comprises the

estuary of the Garavogue River, a relatively short (3km long) river that flows from

Lough Gill. Sligo Harbour is the middle of three important coastal inlets (all

estuaries), which together comprise Sligo Bay. As is the case with the other two

estuaries, it has only a relatively small river flowing into it, which creates a large

mudflat in the bay. Sligo Harbour is separated from Drumcliff Bay to the north by a

peninsula at Rosses Point and from Ballysodare Bay to the south by the Strandhill

peninsula. In the upper reaches of the estuary, the shoreline is dominated by the

industry and housing of Sligo town, while farming dominates the lower reaches. The

Garavogue discharges through Sligo Harbour and the main channel runs along the

northern edge of the embayment. Extensive intertidal sand and mud flats are present

throughout the area, which are exposed at low tide, with the largest sand flats in the

south of the harbour at Cummeen Strand and Dorrins Strand. Several mussel banks

are present throughout these flats, in addition to commercial clam farming being

undertaken close to the main channel at Cummeen Strand. The site extends from

the Harbour at Sligo town to Rosses Point in the north and Killaspug in the south,

and is almost entirely enclosed by Coney Island at the mouth. Consisting mainly of

dunes, Coney Island has some housing on the eastern part.

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4.3. Characteristics of the designated sites

Sections 4.3.1 and 4.3.2 describe the ecological features of the two Natura sites

(Cummeen Strand/Drumcliff Bay SAC and Cummeen Strand SPA) which will be

directly affected by the proposed development (the areas of these sites overlap

within Sligo Harbour). Section 4.3.3 describes the ecological features of Lough Gill

SAC. Three migratory species residing in Lough Gill have the potential to be

impacted/disturbed by the proposed dredging scheme.

4.3.1. Cummeen Strand/Drumcliff Bay SAC (Site code: 000627)

This large coastal site extends from Cullamore in the north-west to Killaspug in the

south-west, and from Sligo town in the south-east to Drumcliff village in the

northeast. It encompasses two large, shallow bays (Drumcliff Bay and Sligo

Harbour), Ardboline and Horse Islands, sand dunes and sand hills at Rosses Point,

Killaspug, Yellow Strand and Coney Island, grassland at Ballintemple and Ballygilgan

(Lissadell) and a variety of other habitats (woodland, salt marsh, sandy beaches,

boulder beaches, shingle, fen, freshwater marshes, rocky sea cliffs, lakes). The site

is largely underlain by Carboniferous limestone, but acidic rocks are also found on

the Rosses Point peninsula. At Serpent Rock in the north-western section of the site

the most complete section of the north-western Carboniferous strata is exposed.

Here are found an excellent series of fossilised corals which, in some strata, stand

out from the rock matrix.

The dominant habitats on the site are estuaries and intertidal sand and mud flats.

Sligo Harbour receives the waters of the Garavogue River, which flows from Lough

Gill, while Drumcliff Bay receives the Drumcliff River which flows from Glencar

Lough. At low tide extensive areas of intertidal flats are exposed in both of these

sheltered estuarine bays. The intertidal flats support a diverse macrofauna, with

invertebrate species such as lugworm (Arenicola marina), cockles (Cerastoderma

edule), sand mason (Lanice conchilega), Baltic tellin (Macoma balthica), spire shell

(Hydrobia ulvae) and mussels (Mytilus edulis) being frequent. Of particular note is the

presence of eelgrass (Zostera noltii and Z. angustifolia) beds in both bays. Both

estuaries and intertidal flats are of conservation significance and are listed on Annex

I of the EU Habitats Directive. Areas of salt marsh fringe both bays in places.

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Table 4-3: Annex I habitats listed on the Natura 2000 Standard Data Form

Qualifying Habitats Code % cover

Mudflats and sandflats not covered by seawater at low tide 1140 46

Estuaries 1130 14

Juniperus communis formations on heaths or calcareous grasslands 5130 1

Petrifying springs with tufa formation (Cratoneurion) 7220 1

Embryonic shifting dunes 2110 1

Fixed dunes with herbaceous vegetation ("grey dunes") 2130 1

Shifting dunes along the shoreline with Ammophila arenaria ("white dunes") 2120 1

Table 4-4: Species present covered by Article 4 of the Directive 70/409/EEC (the Birds Directive) and Annex II of Directive 92/43/EEC (the Habitats Directive) – from the Natura 2000 Standard Data Form

Species Species name Code Birds listed on Annex I of the Birds Directive Branta leucopsis A045

Pluvialis apricaria A140

Limosa lapponica A157

Pyrrhocorax pyrrhocorax A346

Regularly occurring migratory birds not listed on

Annex I of the Birds Directive

Fulmarus glacialis A009

Phalacrocorax carbo A017

Branta bernicla A046

Tadorna tadorna A048

Anas penelope A050

Anas crecca A052

Anas platyrhyncos A053

Mergus merganser A070

Haematopus ostralegus A130

Charadrius hiaticula A137

Pluvialis squatarola A141

Vanellus vanellus A142

Calidris alpina A149

Numenius arquata A160

Tringa totanus A162

Tringa nebularia A164

Mammals listed on Annex II of the Habitats

Directive

Phoca vitulina 1365

Fishes listed on Annex II of the Habitats

Directive

Petromyzon marinus 1095

Lampetra fluviatilis 1099

Invertebrates listed on Annex II of the Habitats

Directive

Vertigo angustior 1014

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Table 4-5: Other species of Flora and Fauna of importance – from the Natura 2000 Standard Data Form

Species Name Type

Draba incana P

Orobanche hedera P

Cepphus grylle B

Somateria mollissma B

Rana temporaria A

Lepus timidus hibernicus M

Meles meles M

(B = Bird; M = Mammal; A = Amphibian; P = plant)

4.3.1.1. Conservation Objectives for Cummeen Strand SAC

The current conservation objectives for Cummeen Strand/Drumcliff Bay SAC (Site

code: 000627) have been received from NPWS (NPWS, 2011a) however these may

change prior to the site being fully designated. The objectives are:

European and national legislation places a collective obligation on Ireland and its

citizens to maintain at favourable conservation status areas designated as candidate

Special Areas of Conservation. The Government and its agencies are responsible for

the implementation and enforcement of regulations that will ensure the ecological

integrity of these sites.

According to the EU Habitats Directive, favourable conservation status of a habitat is

achieved when:

its natural range, and area it covers within that range, is stable or increasing,

and

the ecological factors that are necessary for its long-term maintenance exist

and are likely to continue to exist for the foreseeable future, and

the conservation status of its typical species is favourable as defined below.

The favourable conservation status of a species is achieved when:

population data on the species concerned indicate that it is maintaining itself,

and

the natural range of the species is neither being reduced or likely to be

reduced for the foreseeable future, and

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there is, and will probably continue to be, a sufficiently large habitat to

maintain its populations on a long-term basis.

Objective 1: To maintain or restore the favourable conservation condition of the

Annex I habitat(s) and/or the Annex II species for which the SAC has been selected:

It is noted that some species which are listed on the Standard data Form are not

included in these conservation objectives. These species are:

Birds Directive Annex I listed bird species

Regularly occurring migratory birds not listed on Annex I of Council Directive

79/409/EEC (the Birds Directive)

Other species of interest

Species of interest in these categories are listed in Table 4-3, Table 4-4 and Table

4-5 above.

4.3.1.2. Other Annexed species present within the SAC

Annexed species which are not listed on the Natura 2000 Standard Data Form or

included in the conservation objectives, are shown in Table 4-6.

Table 4-6: Annexed species present within the Natura site but which are not listed on the Natura 2000 Standard Data Form or on the Conservation Objectives for the Site.

Annexed species Code

Otter – Lutra lutra [Annex II and Annex IV] 1355

River lamprey - Lampetra fluviatilis [Annex II] 1099

Atlantic salmon – Salmo salar (in freshwater) [Annex II] 1106

Whilst not listed for in the conservation objectives for the SAC, otter are certainly

present in Sligo Harbour. (Their Annex IV status affords them protection wherever

they occur). Atlantic salmon, present (and protected in freshwater) in the Lough Gill

SAC (Site Code: 001976) will also transit through the Cummeen Strand/Drumcliff Bay

SAC during migration to and from sea. It is important that their progress through the

site is not impeded during critical migration periods.

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4.3.2. Cummeen Strand SPA (Site code: 004035)

Cummeen Strand is a large shallow bay stretching from Sligo town westwards to

Coney Island. It is one of three estuarine bays within Sligo Bay, with Drumcliff Bay to

the north and Ballysodare Bay to the south. The Garavogue River flows into the bay

and forms a permanent channel.

At low tide, extensive sand and mud flats are exposed. These support a diverse

macro-invertebrate fauna which provide the main food supply for the wintering

waterfowl. Invertebrate species such as lugworm (Arenicola marina), ragworm

(Hediste diversicolor), cockles (Cerastoderma edule), sand mason (Lanice

conchilega), Baltic tellin (Macoma balthica), spire shell (Hydrobia ulvae) and mussels

(Mytilus edulis) are frequent. Of particular note is the presence of eelgrass (Zostera

noltii and Z. angustifolia) beds, which provide a valuable food stock for herbivorous

wildfowl. The estuarine and intertidal flat habitats are of conservation significance

and are listed on Annex I of the EU Habitats Directive. Areas of salt marsh fringe the

bay in places and provide roosting sites for birds during the high tide periods. There

are sand dunes at Killaspug Point and Coney Island, with a shingle spit at

Standalone Point near Sligo town. Cummeen Strand is of ornithological importance

as it supports important concentrations of wintering waterfowl. The site supports an

Internationally Important flock of Brent Geese (peak of 232 individuals in the winter of

1999/00, with the mean of peak monthly counts in the period 1996/99 (except 1998)

being 228, peaking at 309) and Nationally Important populations of a further two

species – Oystercatcher 891 and Redshank 501 (all figures are average peaks for

the period). Other species which occurred in significant numbers included Shelduck

80, Wigeon 178, Teal 70, Mallard 170, Red-breasted Merganser 17, Golden Plover

567, Lapwing 734, Knot 18, Sanderling 18, Dunlin 601, Bar-tailed Godwit 57, Curlew

546, Greenshank 18 and Turnstone 80. Whooper Swans also occurred (9), though

they are not regular visitors. The presence of Golden Plover, Bar-tailed Godwit and

Whooper Swan is of particular note as these species are listed on Annex I of the EU

Birds Directive.

This site is of high ornithological importance, with one species having a population of

International Importance and two having populations of National Importance. In

addition, there are three species that are listed on Annex I of the Birds Directive. The

site is also important as a component of the much larger Sligo Bay complex.

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Table 4-7: Species present covered by Article 4 of the Directive 70/409/EEC (the Birds Directive) – from the Natura 2000 Standard Data Form

Species Species name Code Birds listed on Annex I of the Birds Directive Pluvialis apricaria A140

Limosa lapponica A157



Branta bernicla A046

Tadorna tadorna A048

Anas penelope A050

Anas crecca A052


Mergus serrator A069

Haematopus ostralegus A130

Charadrius hiaticula A137

Vanellus vanellus A142

Calidris canutus A143

Calidris alba A144

Calidris alpina A149

Numenius arquata A160

Tringa totanus A162

Tringa nebularia A164

Arenaria interpres A169

Larus ridibundus A179

Larus canus A182


Species Name Type

Ardea cinerea B


4.3.2.1. Conservation Objectives Cummeen Strand SPA (Site code: 004035)

The current conservation objectives for Cummeen Strand SPA (Site code: 004035)

have been received from NPWS (NPWS, 2011b) however these may change prior to

the site being fully designated.

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achieved when:


and






and





The objectives are: To maintain or restore the favourable conservation condition of

the Bird species listed as Special Conservation Interests for this SPA specifically:

[wintering] Branta bernicla hrota

[wintering] Haematopus ostralegus

[wintering] Tringa totanus

[habitat] Wetlands & Waterbirds

(See also Table 4-7 and Table 4-8.)

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4.3.3. Lough Gill SAC (Site code: 001976)

This site comprises Lough Gill with Doon Lough to the north-east, the Bonet River as

far as but not including Glenade Lough, and a stretch of the Owenmore River near

Manorhamilton in Co. Leitrim. Lough Gill itself, 2 km east of Sligo town, lies at a

geological junction of ancient metamorphic rocks which produce acid groundwater,

and limestone which dissolves in the groundwater. The large 8 km long lake has

steep limestone shores and underwater cliffs and is over 20m deep in places. The

lake appears to be naturally eutrophic, and thus represents a habitat listed on Annex

I of the EU Habitats Directive.

The site is a candidate SAC selected for alluvial wet woodlands, a priority habitat on

Annex I of the E.U. Habitats Directive. The site is also selected as a candidate SAC

for old Oak woodlands and natural eutrophic lakes, both habitats listed on Annex I of

the E.U. Habitats Directive. The site is also selected for the following species listed

on Annex II of the same directive - Sea Lamprey, River Lamprey, Brook Lamprey,

White-clawed Crayfish, Atlantic Salmon and Otter. The aquatic macrophyte flora is

very limited, probably due to the rapid increase in depth around most of the margin.

The site is of considerable importance for the presence of four Red Data Book fish

species that are listed on Annex II of the E.U. Habitats Directive - Brook Lamprey

(Lampetra planeri), River Lamprey (Lampetra fluviatilis), Sea Lamprey (Petromyzon

marinus) and Atlantic Salmon (Salmo salar). The Lough Gill system gets a very early

run of spring salmon while the Bonet holds stocks of salmon from spring right through

to the end of the season. White-clawed Crayfish (Austropotamobius pallipes), Otter

and Pine Marten are well established on this site, the former, both being Annex II

species.

The site is of importance for three habitats listed on Annex I of the E.U. Habitats

Directive, including one with priority status. It is also noted for the high number of rare

or scarce animal and plant species. Detailed ecological studies have been carried out

on the lake in recent years and a management plan for Lough Gill catchment was

produced in 1998 for Sligo County Council.

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Table 4-9: Annex I habitats listed on the Natura 2000 Standard Data Form

Qualifying Habitats Code % cover

Natural eutrophic lakes with Magnopotamion or Hydrocharition-type vegetation 3150 78

Old sessile oak woods with Ilex and Blechnum 91a0 3

*Alluvial forests with Alnus glutinosa and Fraxinus excelsior (Alno-Padion,

Alnion incanae, Salicion albae)

91e0 1

Table 4-10: Species present covered by Article 4 of the Directive 70/409/EEC (the Birds Directive) and Annex II of Directive 92/43/EEC (the Habitats Directive) – from the Natura 2000 Standard Data Form

Species Species name Code Birds listed on Annex I of the Birds Directive Sterna hirundo A193

Alcedo atthis A140



Larus ridibundus A179

Bucephala clangula A067

Athya fuligula A061


Mammals listed on Annex II of the Habitats

Directive

Lutra lutra 1365

Fishes listed on Annex II of the Habitats

Directive


Lampetra planeri 1096


Species Name Type

Draba incana P

Orobanche hedera P

Cepphus grylle B

Somateria mollissma B

Rana temporaria A

Lepus timidus hibernicus M

Meles meles M


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4.3.3.1. Conservation Objectives for Lough Gill SAC

The current conservation objectives for Lough Gill SAC (Site code: 000627) have

been received from NPWS (NPWS, 2011a) however these may change prior to the

site being fully designated. The objectives are:







achieved when:


and






and





Objective 1: To maintain or restore the favourable conservation condition of the

Annex I habitat(s) and/or the Annex II species for which the SAC has been selected:

[1092] Austropotamobius pallipes

[1095] Petromyzon marinus

[1096] Lampetra planeri

[1099] Lampetra fluviatilis

[1106] Salmo salar (only in fresh water)

[1355] Lutra lutra

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[3150] Natural eutrophic lakes with Magnopotamion or Hydrocharition-type

vegetation

[91a0] Old sessile oak woods with Ilex and Blechnum in the British Isles

[91e0] *Alluvial forests with Alnus glutinosa and Fraxinus excelsior (Alno-Padion,

Alnion incanae, Salicion albae)

Three migratory species (Petromyzon marinus, Lampetra fluviatilis and Salmo salar)

specified in the Lough Gill SAC Conservation Objectives spend key portions of their

lives residing in or transiting through the Cummeen Strand/Drumcliff Bay SAC.

4.3.3.2. Endangered fish species Lough Gill SAC

A further migratory species Anguilla anguilla (European Eel) is present in the Lough

Gill system. Animals of this species spend key portions of their lives transiting

through the Cummeen Strand/Drumcliff Bay SAC. The European Council (EC)

Regulation No 1100/2007 establishing measures for the recovery of the stock of

European Eel was published in September 2007. The Regulation required, by 1 July

2009, all member states that contain natural habitats of the European Eel to establish

eel management plans at a river basin scale. The objective of these plans was to

permit the escapement to the sea of at least 40% of the silver eel biomass [relative to

the estimated stock levels in the absence of human influences], through various

measures including reducing commercial and recreational fisheries, restocking,

measures to improve habitats and make rivers passable, transportation of silver eels

to the sea and monitor eel status in each basin.

The following section of this statement details the results of desk and field studies

carried out the increase the depth of knowledge on the area surrounding the

navigation channel where the proposed dredging works are to be carried out prior to

assessment of potential impacts and mitigation measures relating to the proposed

dredging works.

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4.4. Desk Study

4.4.1. Intertidal habitats

The Aquatic Services Unit (ASU), University College Cork, has carried out several

intertidal studies in the Sligo Bay area and within Sligo Harbour. Recent intertidal

work carried out by ASU in the Sligo Harbour area include:

A survey covering a small area in the south west corner of Dorrins Strand,

2005 (carried out as part of an EIS for a proposed extension of the Sligo

airport site). 12 stations were sampled in a relatively small study area.

Samples taken included faunal cores (x3) and samples for granulometric and

organic carbon analysis.

An assessment of the wider intertidal benthic community of Sligo Harbour,

2007 (carried out as part of an EIS for a proposed extension of the Sligo

airport site) in which 30 stations were sampled over a large area of Sligo

Harbour. The sampling regime included faunal cores (x5), 1 x 1m2 quadrat

described physically and biologically, 1 x 0.25m2 quadrat was marked out and

excavated to a depth of 20cm. Sediment was sieved in situ through a 5mm

mesh sieve. Samples were taken for granulometric and organic carbon

analysis.

A survey of Mudflats and Sandflats in Ireland, 2007 (commissioned by the

National Parks and Wildlife Service). This survey consisted of several shore

transects in the Sligo Bay area. Three stations were investigated on each

transect – a High, Mid and Low shore station. At each of these stations,

faunal cores (x5), a 1 x 1m quadrat was excavated using a hand spade to a

depth of 20cm and examined for macrofaunal content. A core was also taken

for granulometric and organic carbon analysis.

4.4.1.1. Aquatic Services Unit, UCC – Dorrins Strand 2005

The following is taken from ASU, 2005. The area of Sligo Bay surveyed at Dorrins

Strand was dominated by an expansive sandy intertidal area ringed for the most part

by a narrow saltmarsh fringe. This site was just to the east of Sligo Airport runway.

Immediately below the saltmarsh fringe the shore was mainly comprised of sand right

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from the top of the shore. This was supplemented just east from where Sligo Airport

runway comes closest to the shore around to Rinn Point by a narrow upper shore

gravel / cobble fringe interspersed with muddy sand in places. This latter was

dominated by the brown seaweed, spiral wrack (Fucus spiralis) with a locally heavy

cover of the green seaweed, Enteromorpha sp., especially common close to where a

small freshwater stream flows onto the shore running east. The stream joins the

shore immediately east of where the small by-road (from the south) reaches the

shore. At low tide, the small stream hugs the shore travelling east to ENE in a

shallow channel on the surface of the sand, eventually joining the main eastwest tidal

channel just off Rinn Point. The intertidal channel of the stream near where it joins

the east-west tidal channel and the tidal channel itself, had significant numbers of

loosely scattered clumps of Enteromorpha and to a lesser extent small clumps of

filamentous brown and red algae (e.g. Ceramium nodulosum). In addition, numerous

small gobies were visible in the shallow water of these channels during low water. A

couple of smaller streams / drainage ditches drain to the shore closer to the airport

runway and these join the main tidal channel via short shallow meandering channels.

The sandy or muddy sand habitats of the shore appear (in May) rather uniform to the

eye with virtually no macroalgal (large seaweed) cover. The most obvious feature is

the moderately dense lugworm (Arenicola marina) burrows which dominate most of

the shore, particularly south of the east-west running low-tide channel. North of this

channel the shore height is slightly higher, and the substrate slightly drier and sandier

and so the lugworm densities are visibly lower. Around all the lower-lying and wetter

areas of the flats e.g. stream channel edges, the lugworm cast density tends to be

highest. During early August much of the soft-sediment intertidal area about 70m to

the south of the east-west flowing tidal channel had a moderate to locally dense

cover of the green filamentous alga Vaucheria sp.

The only area where there is a typical rocky shore community was on the short steep

rock-armoured shore, which begins adjacent to the eastern end of the runway and

runs north east along the shore for a short distance. This is a typical sheltered shore

dominated by brown fucoid seaweeds. The upper shore boulders were virtually

devoid of the yellow and grey lichen zones, which are sometimes evident on such

substrates and the brown seaweed channel wrack is confined to a few scattered

clumps at the top of the shore. This was followed by a better-defined, but narrow

(~0.5m), band of Fucus spiralis and then by the main zone which is dominated by two

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more brown seaweeds: egg wrack (Ascophyllum nodosum) and bladder wrack

(Fucus vesiculosus) forming a dense band of about 3m width and 100% cover. The

lower shore and shallow subtidal were dominated by Fucus serratus (serrated

wrack), Laminaria saccharina (strap weed or sugar wrack) and clumps of the invasive

brown seaweed Sarragassum muticum. Bootlace weed (Chorda filum) was present in

the deeper (>1m) water of the sandy-bottomed channel adjoining the shore at this

point. Most of the mid to lower shore brown algae had other finer seaweed growing

as epiphytes on them including fine filamentous browns and fine red algae such as

Polysiphonia lanosa, Aglaothamnion roseum and Ceramium pallidum. Other, very

infrequent small reds included Hypoglossum hypoglossoides and Apoglossum

ruscifolium on silted rock in the lower shore. Some Enteromorpha was also present

on this shore.

The intertidal fauna was quite sparse and comprised scattered littorinid snails

(including the edible periwinkle Littorina littorea and L. obtusata/mariae), frequent

limpets (Patella vulgata), occasional dog whelks (Nucella lapilis), blue mussels

(Mytilus edulis) and top shells (Gibbula cineraria). Barnacles were not common on

the shore and included Semibalanus balanoides and Elminius modestus. The shore

crab (Carcinus maenas) was also occasionally noted under stones. The lower

boulders on the shore had coatings of silty sand on their surfaces. Small hydroids

(Dynamena sp.) were noted as epizootic on fucoid algae, as was the Bryozoan

Alcyonidium sp. The fine sponge Leucsolenia sp. was noted under stones in the mid-

lower shore, while another sponge, Hymeniacidon perleve was occasionally found on

the sides of silted boulders in the same locations. In the upper sub-tidal large clumps

of the sea squirt (Tunicata) Ciona intestinalis (deep orange form) was present on

brown algal covered boulders.

4.4.1.2. Aquatic Services Unit, UCC Intertidal Survey 2007

An assessment of the wider intertidal benthic community of Sligo Harbour, 2007

(carried out as part of an EIS for a proposed extension of the Sligo airport site). 30

stations were sampled over a large area of Sligo Harbour. The sampling regime

included faunal cores (x5), 1 x 1m² quadrat described physically and biologically, 1 x

0.25m² quadrat was marked out and excavated to a depth of 20cm. Sediment was

sieved in situ through a 5mm mesh sieve. Samples were taken for granulometric and

organic carbon analysis.

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Figure 4: Map showing the location of the 30 intertidal stations surveyed by Aquatic Services Unit, UCC in 2007.

4.4.1.3. Aquatic Services Unit, UCC Intertidal Transect Survey 2007

The following section is taken from Aquatic Services Unit (2007): Aquatic Services

Unit, University College Cork, was employed by the Department of Environment,

Heritage and Local Government to carry out a survey of mudflats and sandflats

across seven intertidal SACs (Special Areas of Conservation) around Ireland. As part

of this survey, ASU undertook a detailed survey of intertidal habitats in Sligo Harbour

– three transects were surveyed in Sligo Harbour itself. An additional four transects

were surveyed in the adjoining SAC of Ballysodare Bay.

4.4.1.3.1. Sligo Harbour Transect 1

Transect 1 (length 1930m) was located along the southern shore of Sligo Harbour.

The shore was backed by a 2 – 3 meter high sea all, which connected directly to the

main road. The upper section of the wall was characterised by the presence of

lichens. At the base of the wall was a band of Enteromorpha ulva. This immediately


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gave way to a band of Fucus sp. attached to cobble within a sediment matrix. There

was evidence of freshwater influence across the area, as a drain was present 10

meters from the start of the transect. The transect crossed a shallow channel

approximately thirty metres from the start of the transect. The upper shore site was

located within the intertidal from the sea wall to the shallow channel. The transect

crossed an extensive mussel bank, which ran in a west-northwest direction across

Cummeen Strand.

This raised bank of mussels measured approximately 35 to 40m across at this point

of the transect. The mid shore area of the transect was characterised by the

presence of a significant amount of standing water (ranging from 50% to nearly 100%

in places). Arenicola sp. casts were abundant at this shore height. A clam farm was

present approximately 1½ km along he transect, and there was evidence of

motorised vehicle use on the sediment. The low water site was taken immediately

adjacent to the main channel. The strandline at Transect 1 returned 25 specimens of

a single species, Orchestia gammarellus.

Figure 5: Figure showing locations of transects surveyed by ASU in Sligo Bay, 2007.


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4.4.1.3.1.1. 20m from the shoreline – T1 high shore station

The sediment at this shore height has been classified as gravelly sand, with a

significant amount of mud present. Standing water was evident at the site, covering

25% of the sediment surface. An anoxic layer was present just beneath the sediment

surface, with evidence of a stone layer at a depth of 10cm. The station was located

approximately 20 meters from a shallow channel which crossed the transect at the

upper shore level. Macoma balthica shells were present on the sediment surface,

and live specimens were recovered in the dig. Enteromorpha intestinalis and Fucus

vesiculosus were present on the sediment surface. No Arenicola sp. casts were

present within this shore height, although a single specimen was recovered in the 1m

dig.

4.4.1.3.1.2. 900m from the shoreline – T1, mid-shore station

This sediment at this station was dominated by fine rippled sand. The anoxic layer

was present at a depth of 2 cm, and presented as a black layer. A thick shell layer

was present at a depth of 15cm. The sediment was under a significant amount of

standing water (~85%). Fifteen Arenicola sp. casts were identified in the quadrat,

although only two specimens were returned in the dig. In addition, large numbers of

dead cockle shells were present on the sediment surface. Enteromorpha intestinalis

and Fucus vesiculosus were present on the sediment surface. The station was

located approximately 100m from the raised mussel bank.

4.4.1.3.1.3. 1950m from the shoreline – T1, low shore station

This station was taken immediately adjacent to the main channel at low water.

Sediment at this site was characterised as rippled gravelly sand. There was no

visible fauna present on the sediment surface, although the red algae Ceramium sp.

was present. The depth of the anoxic layer at this site was 10cm. Approximately 30%

of this site was under standing water, which was present between the ripples.


Transect 2 (length 1990m) was located along the southern shore of Sligo Harbour

running from the shoreline near Coney Island causeway in a north-northwest

direction to the lighthouse on Oyster Island. The shore was backed by a narrow strip

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of saltmarsh and agrcultural land giving way to fine rippled sand with a layer of water

over it. This gave way to an extensive area of rippled sand with extensive amounts of

Cerastoderma edule and Arenicola marina casts on the sediment surface. At the low

water site Lanice conchilega dominated. C. edule were also evident at low water.

The strandline at Transect 2 returned 9 specimens of Orchestia meditteranea and 5

specimens of Ligia oceanica.

4.4.1.3.2.1. 185m from the shoreline – T2, upper shore station

The sediment at this station was dominated by fine sand. The site was located in a

water channel, with a very weak flow (100% cover). Dead cockle shells were present

on the sediment surface. Arenicola casts were present on the sediment surface (3

per square meter) and 1 was returned in the dig. There was occasional

Enteromorpha present at this shore height.


The sediment at this station was characterised as rippled muddy sand. The anoxic

layer was present at 4cm depth. There was a significant amount of standing water

present within this area, with ~75% of the sediment covered with a thin layer of

standing water. There were significant numbers of Cerastoderma edule on the

sediment surface. Arenicola casts were present (2 per square meter) although none

were returned in the dig. There were occasional clumps of Enteromorpha present at

this shore height.

4.4.1.3.2.3. 1990m from the shoreline – T2, low shore station

This station was taken immediately adjacent to the main channel at low water.

Sediment at this site was characterised as rippled fine sand. The anoxic layer at this

site was 15cm deep. Standing water (10%) was present between the ripples on the

sediment surface. Lanice conchilega and Cerastoderma edule were abundant and

algae were present in significant numbers on the sediment surface (Enteromorpha

and Ceramium).

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Transect 3 (length 135m) was located along the outer part of Sligo Harbour between

the mainland, near Sligo Airport and Coney Island. There was a channel running

between Coney Island and the mainland. The shore was backed by a dune system,

giving way to a cobble/boulder with a large amount of algal drift at the uppermost part

of this. This leads to a soft mobile sand area with occasional clumps of Fucus

vesiculosus and Fucus serratus. At 50 meters this sand becomes more firm.

Arenicola casts were present from this location to the low water site. At 60 meters,

the sediment becomes wet, and Enteromorpha became more abundant. The bottom

of the transect is characterised by shell and sand with large numbers of

Enteromorpha. On both sides of this transect, the shoreline was dominated by a

fucoid covered boulder shore, with limited soft sediment in evidence.

The strandline at transect 3 returned 94 specimens of a single species, Orchestia

gammarellus.

4.4.1.3.3.1. 20m from the shoreline – T3, upper shore station

The sediment at this station was characterised as rippled gravelly sand. The

sediment was very dry and there was no evidence of fauna on the sediment surface.

The anoxic layer was not visible at this site.


The sediment at this station was dominated by wet sand. The anoxic layer was

present just beneath the sediment surface. Enteromorpha was present on the

sediment surface with occasional clumps of Fucus present along the shore height.

Arenicola casts were present at this shore height (6 per square meter), although only

1 specimen was returned in the dig.

4.4.1.3.3.3. 130m from the shoreline – T3, lower shore station

This station as taken immediately adjacent to the main channel at low water.

Sediment at this site was characterised as gravelly sand. The anoxic layer was

present just below the sediment surface. The sediment surface was dominated by

the fucoid algae Fucus serratus, F. vesiculosus, with Enteromorpha present in

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significant numbers. Arenicola casts were present (1 per square metre) and a single

specimen was returned in the dig.

4.4.1.4. BIOMAR and Office of Public Works intertidal surveys

A number of intertidal areas were surveyed by the BIOMAR team and Office of Public

Works in 1996 (Picton & Costelloe, 1998). These are shown in Figure 6. (Site two

was a subtidal station surveyed using SCUBA equipment off Ballyconnell Point,

South Donegal Bay). The data collected at these stations give a good indication of

the variation of floral and faunal communities to be found along this stretch of coast.

Sites were surveyed in detail with substrates, site exposures, habitats, biotopes and

species present and abundance scales all recorded. Sediment cores were taken at

several of the sites where sedimentary habitats dominated. (Detailed data for each of

these stations are presented in Appendix A of this report).

Figure 6: Location map for the sites surveyed by BIOMAR and OPW teams in Sligo Bay 1996.

Sites 6, 7 and 8 are in closest proximity to the dredging work proposed for Sligo

Harbour. Site 6 was located in an exposed area at Rosses Point on the western edge

of the small peninsula separating Sligo Harbour from Drumcliff Bay. This is a gently

sloping beach composed of fine, well-sorted sand backed by low dunes with little

surface evidence of life. Sampling showed the presence of polychaetes (Angulus

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tenuis) and bivalves (juvenile Donax sp.). Brown shrimp (Crangon sp.) were present

in a midshore runnel.

Site 7 was located in a very sheltered area at Dorrins Strand on the south shore of

Sligo Harbour. It ran from the southern end of the roadway to Coney Island across

the large sand flat to the edge of the main channel to the south of Oyster Island

(approximately 2km). The shore was backed by grassland and a narrow strip of salt

marsh giving way to rippled fine sand with a shallow layer of standing water. A wide

(100m) shallow channel (2-5cm), split by a sandbar, was located approximately

100m from the shore. The bed of the channel was soft rippled sand with frequent

cockles, Arenicola sp. casts and frequent clumps of Enteromorpha sp. on the

surface. To the north of this channel the sand was firmand, for the most part, covered

with a layer of standing water and had an anaerobic layer 1-2cm below the surface.

A. marina castings were visible on the surface at densities of 1-9 per metre squared

with Cerastoderma edule present in the top 10-15 cm of sediment at densities of 1-5

per metre squared. Fine tube worms were also common. At 1.75km out from the

shore the surface rose gently to the top of a large sandbank running adjacent to the

main channel. The sediment on the bank was coarse and dry with an ARPD layer

greater than 25cm below the surface. At 2km out from the shore the sandbank

sloped down to the main channel with a dense bed of Lanice conchilega and

filamentous brown algae 50m from the channel. Ulva sp. was also present attached

to worm tubes with an anoxic layer 10cm below the sediment surface in the coarse

sand and broken shell at the channel edge.

Site 8 was located at Cummeen Strand in Sligo Harbour. It was taken from the sea

wall next to Gibraltar Point on the southern shore to the main channel on the north

side of the bay. This transect was approximately 2km long and crossed a small

channel about 50m from the sea wall. It started with an area of mud, gravel and

stone sloping gently to the shallow channel and was characterised by Enteromorpha

spp., Ulva sp., Fucus ceranoides and Scrobicularia plana. Beyond the channel the

beach had a short steep upward slope characterised by small burrows containing

very small gastropods. The beach appeared flat for 600m and was characterised by

Arenicola marina for the first 300m and then by a mixture of A. marina for the first

300m and then by a mixture of A. marina and Cerastoderma edule. Between 600m

and 700m there was a dense mussel bed with mussel and dead cockle shells

banded together on the shoreward side. Some F. vesiculosus and Enteromorpha sp.

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were present on the bed. Seaward of this the shore sloped very gently to the channel

and was covered with standing water 1.5cm deep with small cockles present for the

next 200m. After this, cockles were occasional as were A. marina casts. The sand

was very flat with small tubes present. Close to the channel the sand became rippled

and algae (in particular Polysiphonia sp. or Ceramium sp.) were attached to dead

cockle shells. Close to the channel the sand became rippled and algae, in particular

Polysiphonia sp. or Ceramium sp. were attached to dead cockle shells. Lanice

conchilega were frequent sat the channel edge. Across most of the beach

Enteromorpha spp. were present attached to dead shells. The anoxic layer varied

from 1 to 10cm below the sediment surface but was generally 1cm to 5cm beneath

the surface. Clam beds were present on the beach.

4.4.2. Subtidal habitats

4.4.2.1. BIOMAR and Office of Public Works subtidal surveys

A single subtidal station in close proximity to the proposed work was surveyed by the

BIOMAR team in 1996. This site was located off Ballyconnell Point and was adjacent

to the very exposed headland near the entrance to inner Sligo Bay. The dive

documented a large subtidal cliff with abundant jewel anemones (Corynactis viridis).

This stretched from 13m to approximately 26m BCD. Stepped limestone bedrock was

documented at the bottom of the cliff with Devonshire cup-corals (Caryophyllia

smithii) and jewel anemones (Corynactis viridis). This type of subtidal environment is

typical of the more exposed, outer areas of Sligo Harbour. The inner harbour (east of

Coney Island) is typically characterised by sedimentary habitats. This includes the

deepened approach channel for the harbour.

Subtidal habitat in Sligo Harbour is very limited in areal extent when compared with

intertidal habitat and is largely confined to the deeper channels present – the primary

areas being the navigation approach channel along the northern shore of the harbour

and the channel surrounding Oyster Island.

4.4.3. Birds

Sligo Bay has long been noted for its importance in terms of habitat for wetland birds.

In 1974, a Department of Lands, Forest and Wildlife Service and Irish Wildbird

Conservancy report listed Cummeen Strand as a site of International importance (for

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Brent Goose) and Lissadell as a site of National importance (for barnacle Goose). In

the mid 1990s, two surveys were initiated to monitor Ireland’s wetlands and their

waterbirds – the Irish Wetland Bird Survey in the Republic of Ireland and the Wetland

Bird Survey in Northern Ireland. Crowe (2005) draws together the information

collected by these surveys over the period 1994 to 2001 and identified four areas of

international importance and five of national importance in for wetland birds in County

Sligo. These are as follows:

Internationally important sites:

1. Ballysodare Bay

2. Sligo Harbour

3. Drumcliff Bay Estuary

4. Lough Gara

Sites of national importance:

1. Killala Bay

2. Lough Arrow

3. Streedagh Estuary

4. Outer Sligo Bay North

5. Outer Sligo Bay-Dunmoran

Ballysodare Bay is the most southerly of the three Bays that comprise the Sligo Bay

wetland complex. It extends west and north of the town of Ballysodare for about

10km. It contains extensive intertidal sand and mudflats, which are largely exposed

at low tide and is narrowed at the mouth by a sand-spit and dune system. A range of

habitats fringe the bay, including an old empoldered oyster farm at Tanrego.

A majority of Ballysodare Bay has been covered during all seasons other than in

1997/98. A total of 11 count units has been described, seven of which have been

regularly covered.

Ballysodare Bay supports internationally important numbers of Light-bellied Brent

Goose and nationally important numbers of a further four species, all waders (Dunlin,

Bar-Tailed Godwit, Redshank and Green Shank). This section of Sligo Bay has

certainly become increasingly favoured by wintering waterbirds, with overall numbers

having increased significantly (by 182%) since the Winter Wetlands Survey (1984-

86). There have been increases in most wader species, particularly Dunlin and

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Redshank, and also Lapwing (by 167%) and Curlew (193%). Ringed Plover has also

increased slightly, though the national population has also increased since the earlier

survey and their numbers here are no longer of national significance. Notable

wildfowl increases include Shelduck (by 63%), Wigeon (143%) and Teal (97%).

4.4.3.1. Birds – Activities and threats

In 2002, the Minister for the Marine and Natural Resources provided a grant to

enable the Sligo Harbour Authority to initiate its Sligo Harbour Regeneration Plan.

This plan included development of apartments and retail units in the harbour, and to

use the income to boost commercial activity in the harbour. This would involve

extensive dredging of the harbour to allow commercial shipping traffic through.

Further habitat destruction would be caused by the dumping of dredge spoil onto the

mudflats. The development of apartments and retail units, together with increased

commercial activity, in Sligo Harbour could affect adjacent bays (Drumcliff and

Ballysodare) (Crowe, 2005). There is a stone quarry at Abbeytown on the south

shore of Ballysodare Bay, and waste rock and other materials have at times been

dumped on the foreshore of the bay.

Further reduction in habitat quality at this site has resulted from increased intertidal

shellfish cultivation and recreation. There is a commercial scale clam-farm and a

number of privately owned oyster farms which operate throughout this site and the

adjacent Drumcliff Bay. Fishing and boating are common year-round recreational

activities in the three Sligo bays.

Sligo airport is located at Strandhill, between Ballysodare Bay and Sligo Harbour.

Occasional disturbance is caused by low-flying aircraft associated with the airport at

Strandhill. Disturbance is also caused by marsh shooting in the upper reaches of the

bay.

A causeway exists that allows motor vehicles to access Coney Island. The

movement of vehicles across the causeway to Coney Island probably causes far

more disturbance to bird populations than occasional low-flying aircraft from nearby

Sligo airport (see Figure 7). Intensive tyre tracks can be seen in aerial imagery

(visible at Microsoft Bing Maps www.bing.com/maps/) and these cover quite a wide

area along this causeway between Scarden Mór and Coney Island – far more than

would be expected from simple two-way traffic along this route.

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Figure 7: Intertidal tyre tracks at Coney Island, Sligo Harbour (image screen grab taken from www.bing.com/maps/ December 2010).

Aquaculture is present in Sligo Harbour, though it is not as extensive as at either of

the other two inlets of Sligo Bay.

4.4.3.2. Sligo Harbour - bird counts

In terms of bird counts, Sligo Harbour was entirely covered at least once during each

of the four seasons between 1996/7 and 2000/01. The three Sligo Bays are usually

counted within a 10-day period. A total of 14 count units has been described, seven

of which are now regularly covered.

Sligo Harbour is internationally important for Light-bellied Brent Goose and nationally

important for Oystercatcher, Redshank and Greenshank. Overall, numbers of

waterbirds have remained consistent since the Winter Wetlands Survey (1984-86)

(marginal 6% decline). However there have been several changes at species level.

Number of light-bellied Brent Geese and Ringed Plover have declined substantially,

and the latter species no longer occurs in internationally important numbers (having

decreased by 81%). Other declines include Grey Heron (by 32%), Red-breasted

Merganser (27%) and Bar-tailed Godwit (33%). The most notable increases include

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Shelduck (by 134%), Mallard (35%), Golden Plover (172%), Lapwing (61%), Curlew

(29%), Redshank and Turnstone (35%).

4.4.3.3. Birdwatch Ireland Sligo Branch

The following information is taken from Birdwatch Ireland’s Sligo Branch’s website.

They divide Sligo Harbour into five areas for the purposes of bird watching:

(1) Silver Swan Bay: This area is located between the Hughes and Hyde bridges.

Due to the scouring action of the river, this part consists mostly of bedrock.

Cormorant, Shag, up to 30 Mute Swans, Mallard and Red-breasted Merganser are

usually present in winter. Occasionally, Redshank and Curlew can be found on the

muddier parts. Gulls typically present include Black-headed, Common, and Herring,

while Glaucous and Iceland have also been seen. In recent years Ring-billed Gull

has become an annual visitor. Close to the mouth of the Garavogue Grey Wagtail is

regular, while Dipper is also occasionally present. The only really noteworthy rarity

recorded here to date was a Ross’s Gull.

(2) Cartron Inner Bay: This site is situated between Hughes Bridge and the

Deepwater Quay. It is muddier than the Cartron Inner Bay and consequently attracts

a higher number of waders. The deep channel of the Garavogue is favoured by

Cormorant, Shag, Goldeneye and Red-breasted Merganser. Oystercatcher, Lapwing,

Redshank, Greenshank, Curlew, Snipe, Black-headed, Common, Herring and Great

Black-backed Gull are present on the mudflats in winter. This site is the most

important wintering site for Black-tailed Godwit in County Sligo: between 15 to 20 are

usually present between September and April. Ring-billed Gull is annual, while a

Yellow-legged Gull was recorded in 2003.

(3) Cartron Marsh: This part of Sligo Harbour lies to the north of the peninsula of

Cartron. Similar to Outer Cartron Bay, it is very muddy. Except for Black-tailed

Godwit, all the species mentioned for last site are also present here. In addition,

Brent Goose, Cormorant, Shag, Shelduck, Teal, Wigeon, Goldeneye, Red-breasted

Merganser, Ringed Plover, Turnstone, Redshank, Greenshank and Dunlin can be

found here. Curlew Sandpiper occurs regularly in September. Occasional visitors

include Red-throated Diver, Great Crested Grebe, Grey Plover, Ruff and Lesser

Black-backed Gull. The closure of the nearby municipal landfill has affected the

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number of Glaucous and Iceland Gulls wintering at this site. Formerly uncommon

winter visitors, they are now seen only irregularly.

(4) Cummeen Strand: This encompasses the main bulk of Sligo Harbour estuary.

Consisting of the deep channel of the Garavogue and the adjacent large mudflats, it

attracts a diverse range of birds. The channel holds Great Northern & Red-throated

Diver, Great Crested Grebe, Cormorant, Shag, Goldeneye, Red-breasted Merganser

and Common Guillemot in winter. Also in winter, the main mudflats attract Shelduck,

Teal, Wigeon, Oystercatcher, Ringed Plover, a few Grey Plover, Lapwing, Knot,

Turnstone, Dunlin, Redshank, Greenshank, Bar-tailed Godwit and Curlew, as well as

Black-headed, Common and Great Black-backed Gulls. During the summer, Lesser

Black-backed Gull, Common and Sandwich Terns can be seen here. Cummeen

Strand is one of the main staging points of Brent Goose in Ireland. Arriving in late

September, up to 400 can be seen at a time. Coney Island, which is accessible via a

causeway, attracts a very large flock of Golden Plovers (around 5,000). In late

summer/early autumn, such a flock may well include something interesting! At this

time of year the gardens on the island should be checked for any migrants. A juvenile

Buzzard in September 2003, a very rare bird in County Sligo, shows the potential of

this island. A flock of around 30 Twite also winter here. Rarities to have occurred in

the Cummeen Strand include two Forster’s Terns in March 2003 and a Little Egret in

June 2003.

(5) Rosses Point: This is an ideal place for scanning Sligo Bay. Between October

and March, Great Northern & Red-throated Diver, Great Crested Grebe, Cormorant,

Shag, Eider, Common Scoter, Long-tailed Duck, Goldeneye and Red-breasted

Merganser can be seen from here. In February 2004, three Slavonian Grebes and

several Velvet Scoters were present. Both of these species have only been seen

here on a very few occasions, and these recent records suggest that they may be

under-recorded in County Sligo. Notably, a White-billed Diver was recorded here in

1977.

4.4.3.4. Drumcliff Bay Estuary

Drumcliff Bay is the most northerly of the Sligo Bay sites. It includes the estuary of

the Drumcliff River which flows from Glencar Lough on the Sligo/Leitrim county

boundary, approximately 7km to the east. This site is almost divided in two by a north

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to south oriented peninsula at the north side of the Rosses Point peninsula. The

habitat of the inner section, to the east of this peninsula, is largely estuarine in

character with expansive mudflats, while open sandy coastline stretches west of the

peninsula. The nearshore waters are shallow, and extensive areas of intertidal flats

are exposed at low tide.

Drumcliff Bay was entirely covered at least once during each of four seasons

between 1994/95 and 1999/2000 inclusive. A total of 13 count units has been

described, eight of which are now regularly monitored. Map boundaries were

available for the five count units of the inner section of the bay only. A further three

count units include the more exposed outer sections of Drumcliff Bay west to, and

including, Raghly Harbour. The Rosses Point beaches, situated between Drumcliff

Bay and Sligo Harbour are also occasionally counted.

Drumcliff Bay is internationally important for Barnacle Goose and nationally important

for Sanderling and Bar-tailed Godwit. There has been a substantial increase in the

number of waterbirds overall (74%) since the Winter Wetlands Survey (1984-86).

This includes increases in Barnacle Goose, Oystercatcher (244%) and Curlew (51%).

There have been declines in Light-bellied Brent Goose (by 71%) and Knot (49%).

The Barnacle Goose flock is usually recorded feeding in the fields around Lissadell

and Ballintemple to the northeast and northwest of the bay respectively. High

numbers of Sanderlings are regularly recorded on the Lower Rosses, the stretch of

sandflats that link Drumcliff Bay with Sligo Harbour. Bar-tailed Godwits tend to

concentrate on the sandy stretches of the outer section of the bay, particularly on

Ardtermon and Ballygilgan Strands. The majority of the other wildfowl and wader

species are usually recorded in the inner section of the site.

Activities and threats for Drumcliff Bay estuary are largely the same as for Sligo

Harbour.

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4.4.4. Marine Mammals

4.4.4.1. Whale and Dolphin Populations

An assessment of the proposed development on marine mammals (i.e. otters, seals,

whales and dolphins) was carried out using relevant published literature and

information on local sightings from reputable sources.

Due to lack of information, cetaceans are not included in the Irish Red Data Book

(Whilde, 1993). Many of the species present in Irish waters are threatened – better

information is needed on their status, numbers, distribution and threats. The Irish

Whale and Dolphin Group (IWDG) was set up to gather data on cetacean

occurrences.

Figure 8: Marine mammal sightings in the County Sligo area 2010-12.

All records are validated and available on www.iwdg.ie.

Figure 8 shows a map plotting marine mammal sightings in the sea around County

Sligo between 2010 and 2012 (www.iwdg.ie, 2012). Species recorded in the Sligo

Harbour area and adjacent areas are dominated by dolphins and harbour porpoises.

Details of specific sightings in Sligo Harbour are given in Appendix D. Further

other

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information on marine mammals is given in Chapter 5.4 of the Environmental

Appraisal Report.

4.4.4.2. Seal populations

Harbour Seal

Harbour Seals (also known as “Common Seals”) have established themselves at

terrestrial colonies (or haul-outs) along all coastlines of Ireland, which they leave

when foraging or moving between areas, for example, and to which they return to

rest ashore, rear young, engage in social activity, etc. These haul-out groups of

harbour seals have tended historically to be found among inshore bays and islands,

coves and estuaries (Lockley, 1966; Summers et al., 1980), particularly around the

hours of lowest tide. Harbour seals haul-out at terrestrial haul-out sites on the Aran

Islands. A national aerial census of harbour seals in Ireland during 2003 identified

haul-out sites in Ballysadare Bay Co. Sligo where over 250 harbour seals were

recorded and in Killala Bay where approximately 110 seals were recorded (Cronin et

al., 2004, 2007). These counts, which are conducted during the seals annual moult

are considered to represent about 60-70% of the total number of seals using the

area. Therefore there are approximately 500-600 harbour seals using haul-out sites

within 40km of Sligo harbour, assuming the population has not changed since the

2003 census. Recent findings from tagging harbour seals in SW Ireland suggest that

harbour seals are local foragers, generally staying within 20km of their haul-out sites

(Cronin et al., 2008). It is highly likely that harbour seals from haul-out sites in

Ballysadare Bay use the waters of Sligo Harbour.

Harbour seals are most vulnerable at their terrestrial haul-out sites during breeding

and moulting periods. These events occur between June and September in Ireland.

However the terrestrial haul-out sites in the Ballysadare area are not located in close

proximity to Sligo Harbour and therefore there is no considered threat of physical

disturbance at the haul-out sites by the proposed works.

In addition to the identified terrestrial sites, the surrounding waters are likely to be

critical habitat for harbour seals, for feeding and/or for navigation to more offshore

foraging areas. Results from a study by the Coastal and Marine Research Centre

(CMRC) on the haul-out behaviour of harbour seals in southwest Ireland in recent

years suggests that harbour seals spend up to 80% of their time at sea (Cronin,

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2007; Cronin et al., 2008). Similar behaviour patterns have been seen in studies of

harbour seals in Scotland (Sharples, SMRU pers comm, Thompson & Miller, 1990).

Unlike grey seals harbour seal adults continue to forage during the breeding season

(Bonnes et al., 1994). In addition the mating strategy is based on males diving and

calling at aquatic display sites (Van Parijs et al., 1997, 2000, Hayes et al., 2004).

Disturbance from anthropogenic noise during this period could potentially affect

mating success.

The hearing range of harbour and grey seals extends over wide frequencies,

including the ultrasonic spectrum. The area of best hearing is between 8 and 25

kHz, with acute hearing also at lower frequencies (Møhl 1968; Terhune & Turnbull

1995)

Considering the relatively large population of harbour seals using waters in Sligo Bay

and the proximity of haul-out sites to Sligo Harbour, there is high potential for harbour

seal use of the waters in the vicinity of Sligo Harbour and therefore they are the

marine mammal species most at risk to potential detrimental impacts of the proposed

dredging and dumping. Mitigation measures outlined in Section 6.4.8 will minimise

potential impacts of the proposed works.

Grey Seal

Grey seals are distributed throughout Irish coastal waters and commonly seen

hauled out on more exposed shores than the harbour seal (Kiely, 1998). Whilst there

are no large colonies of grey seals on the coastline of Co. Sligo, the bordering

counties provide haul-out sites for a significant proportion of the national population

of grey seals. A national census of the grey seal population in 2005 estimated

between 795-1022 grey seals use breeding sites in Co. Donegal and 1351-1737 use

breeding sites in Co. Mayo (Ó Cadhla et al., 2007).

Grey seals use Inishmurray (54.433N 8.660W) and Rathlin O Birne Island (54.664N

8.827W) as breeding sites (Ó Cadhla et al., 2005) and Ballysadare Bay and

Ardboline (54.346N 8.693W) as moult sites (Ó Cadhla & Strong, 2007), where

approximately 50 seals haul-out to moult. Grey seals also use Inishmurray and

Ballysadare Bay as haul-out sites outside of the breeding and moult seasons; over

110 grey seals were recorded on Inishtrahull and 20 in Ballysadare Bay in August

2003 during the harbour seal census (Cronin et al., 2003).

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Grey seals are also most vulnerable at their terrestrial haul-out sites during breeding

and moulting periods. These events occur between September and March in Ireland.

There are no known terrestrial sites for grey seals in the immediate proximity of the

proposed works however the surrounding waters are likely to be a critical habitat for

grey seals, for feeding and/or for navigation to more offshore foraging areas. Grey

seals have a wider offshore foraging distribution than harbour seals and as a result

seals from large breeding colonies on the coasts of Mayo and Donegal will be likely

to use the waters of Donegal Bay and Sligo Bay for foraging and/or navigation and

therefore could potentially be affected by dredging and dumping.

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4.5. Field Survey – AQUAFACT 2010

Numerous intertidal surveys have been carried out in Sligo Harbour in recent years

(see desk Study Section 4.4.1.and Figure 9 below).

4.5.1. Intertidal survey 2010

The objective of the intertidal survey was to carry out:

A general walkover of the shore along

o The shore of the navigation channel

o areas of mussel bank

o clam production areas

o areas of Zostera bed.

Document existing habitats along the route with notes and photographs.

Figure 9: Map showing recent intertidal survey effort, Sligo Harbour. The route of the current intertidal walkover is shown in red. Survey stations & transects carried out by ASU, Cork are also shown. Orthorectified images courtesy RPS Consulting Engineers Ltd.

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Figure 10: Location of observations made during the walkover survey, October 2010.

Aerial photograph ESRI/Bing Maps © Microsoft 2012

4.5.1.1. Materials and Methods - 2010

The survey was carried out on 07th-08th October, 2010. Cloud cover varied between

3/8ths and 7/8ths. The southern shore was accessed at the Scarden More landfall of

the Coney Island causeway. A four wheel drive vehicle was used to transit the shore

during the work. A Trimble® GeoXT™ handheld mapping unit was used to record the

track followed during the survey work and to document various features encountered.

This unit provides real time sub-metre accuracy. Digital photographs were taken

during the survey. The camera time was synchronised with UTC to allow matching of

images to their locations.

Bird species present on the shore were noted during the survey. Photographs and

notes were taken throughout the survey work.

4.5.1.2. Results 2010

4.5.1.2.1. Anthony Lynch - Clam site - Northern Walkover

This survey covered the area shown in Figure 10. Notes and photographs were taken

during the walkover along with GPS coordinates at features of interest. For the most

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part the shoreline was characterised by the presence of clean fine-medium sand with

a variable shell fraction.

The following sections (denoted by letters A-N) correspond with each point marked

by the letters shown in Figure 10 showing the intertidal location of documented

observations.

A. The beach here was composed of fine sand. Numerous wheeled clam trestles

were noted. Small stands of algae (primarily Enteromorpha sp.) were recorded

attached to larger shell fragments on the shore. Small amounts of fucoid algae

(Fucus vesiculosus) were found attached to the trolleys themselves.

Figure 11: Trestles, clam farm site, Sligo Harbour, 07th October 2010.

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Figure 12: Commercial clam park. South west Sligo Harbour, 07th October 2010.

B. A mussel bank I. This area was characterised by a mussel bed. There was a mix

of blue mussel and clams. Algal cover was noted around the margins of the bed.

Figure 13: Mussel bed, Sligo beach, 07th October 2010.

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Figure 14: Mussel bed, close view. A mix of blue mussel and clams.

Figure 15: Algae (primarily fucoids) on mussel bank, Sligo Harbour, October 2010.

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Figure 16: Lugworm feeding casts, near mussel bank, Sligo harbour, October 2010.

C. Seagrass bed. A seagrass bed was noted here. Some algal cover (primarily

Enteromorpha sp.) and lugworm casts (Arenicola sp). were noted.

Figure 17: Seagrass and lugworm feeding casts, Sligo Harbour, October 2010.

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D. Filamentous algal mat over muddy sand flat. The intertidal was quite soft in this

area. An extensive mat of filamentous algae was noted (primarily Vaucheria sp.). A

shallow tidal channel ran through this area.

Figure 18: Vaucheria sp. mat over intertidal muddy fine sand flat, Sligo Harbour, 07th

October 2010.

E. Geese feeding on intertidal flat. A flock of gooses was noted feeding in the

intertidal zone. As well as supporting a seagrass bed of variable density this area had

quite a high density of lugworm feeding casts.

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Figure 19: Gooses feeding on the intertidal sand flat, 07th October 2010.

F. Fyke net on pole in shallow tidal channel. A single fyke net on a pole was noted at

the centre of a shallow tidal channel in the sand.

Figure 20: Fyke net on pole, Sligo Harbour, 07th October 2010

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G. Mussel bank II. Another dense area of mussel bed was recorded in this area.

Figure 21: Mussel bank, Sligo Harbour, 07th October 2010.

H. Mussel bank III. A third extensive area of mussel bank was recorded.

Figure 22: Mussel bank Sligo Harbour, 07th October 2010.

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I. Commercial clam park (Noel Carter’s). Clam cultivation frames and plots in clean,

rippled fine sands. Some algae were present – Enteromorpha sp. attached to larger

shell fragments etc. on the sand flat, and fucoids on any available hard surfaces

(clam cultivation hardware for example).

Figure 23: Commercial clam park (Noel Carter’s). Sligo Harbour, 07th October 2010

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Figure 24: Clam cultivation hardware, Sligo Harbour, 07th October 2010.

Figure 25: Rippled fine sand surrounding clam cultivation site, 07th October 2010.

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J. Intertidal sands with filamentous algal growth.

Figure 26: Intertidal area with filamentous algal growth, Sligo Harbour, October 2010

4.5.1.2.2. Sligo Intertidal – navigation channel area

A walkover survey was conducted in the intertidal zone to the north of the navigation

channel in Sligo Harbour at low water on 08th October 2010. This survey covered the

area shown in Figure 27. Notes and photographs were taken during the walkover

along with GPS coordinates at features of interest.

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Figure 27: Points of interest near the navigation channel walkover area 07th October 2010.

Aerial photograph ESRI/Bing Maps © Microsoft 2012

The following sections (denoted by letters K-N) correspond with each point marked by the letters shown in Figure 27 showing the intertidal location of each documented observation.

K. Intertidal sand flat with sparse algal cover. The sediment surface here was

composed of quite firm, rippled fine sand. Occasional fragments of shell gravel were

noted. Sparse algal cover (mostly Enteromorpha sp.) was recorded.

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Figure 28: Rippled fine sand with some algae, 08th October 2010.

Figure 29: Channel marker, Sligo harbour, 08th October 2010.

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Figure 30: Base of channel marker & training wall, Sligo harbour, 08th October 2010.

L. Clean rippled sand flat. An area of clean, rippled, tide-swept fine sands.

Figure 31: Intertidal sand flat, Sligo Harbour, 08th October 2010.

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M. View along navigation channel towards Sligo.

Figure 32: View towards Sligo along navigation channel, 08th October 2010.

N. A close up view of the harbour training wall. Species recorded included algae

(primarily Fucus vesiculosus), barnacles (Semibalanus balanoides), limpets (Patella

vulgata) and mussels (Mytilus edulis). The intertidal flat at the base of this wall sloped

very gently towards the navigation channel. The sediments here were composed of

muddy fine sand. Small, low ridges of stabilised sediment supporting filamentous

algal growth were noted. Numerous lugworm (Arenicola sp.) feeding casts were

noted.

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Figure 33: Encrusting flora and fauna on the northern Sligo harbour navigation channel training wall, Sligo Harbour, 08th October 2010.

Figure 34: Muddy sand flat adjacent to training wall, Sligo harbour approach channel, 08th October 2010.

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4.5.2. Infaunal survey 2010

4.5.2.1. Sampling Procedure & Processing

To carry out the infaunal survey of Sligo Harbour, AQUAFACT sampled a total of 15

stations. These stations can be seen in Figure 35. Table 4-12 gives the station

coordinates.

Sampling was carried out on the 6th and 7th October 2010 from AQUAFACT’s RIB.

Stations were located using DGPS and this positioning method is accurate to within

ca. 1m. A 0.025m2 grab sampler was used to collect the benthic samples. Three

replicate samples were taken at each of the 15 stations. Data on each sample, e.g.

station number, date, time, depth of sediment, surface features and visible

macrofauna were logged in a field notebook. The faunal returns were sieved on a

1mm mesh sieve, stained with Rhodamine dye, fixed with 10% buffered formalin and

preserved in 70% alcohol. Samples were then sorted under a microscope (x 10

magnification), into four main groups: Polychaeta, Mollusca, Crustacea and others.

The ‘others’ group consisted of echinoderms, nematodes, nemerteans, cnidarians

and other lesser phyla. The taxa were then identified to species level where possible.

An additional sample was taken at Stations 1 to 14 for sediment granulometric

analysis. The sediment samples were taken through the opening on the top of the

grab. Samples were also taken for determination of total organic carbon content. All

samples were stored immediately in a cold room on board the vessel and were

frozen at –20oC on return to the lab.

Particle size analysis was carried out using the traditional granulometric approach

by AQUAFACT. Traditional analysis involved the dry sieving of approximately

100g of sediment using a series of Wentworth graded sieves. The process

involved the separation of the sediment fractions by passing them through a

series of sieves. Each sieve retained a fraction of the sediment, which were later

weighed and a percentage of the total was calculated. Table 4-13 shows the

classification of sediment particle size ranges into size classes. Sieves, which

corresponded to the range of particle sizes were used in the analysis.

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Figure 35: Map showing subtidal sampling locations

Table 4-12: Subtidal station co-ordinates.

Station Easting Northing Longitude Latitude1 163931.8 339745 -8.55414 54.3051 2 165748.2 339095 -8.52616 54.2994 3 167086.5 338473.6 -8.50553 54.2939 4 160270.5 341198.1 -8.61058 54.3179 5 165729 339486.9 -8.5265 54.3029 6 168453.5 337536.8 -8.48444 54.2856 7 162115.5 338540.5 -8.58189 54.2942 8 164677.5 339286.2 -8.54263 54.301 9 166369.5 339066.3 -8.51661 54.2992

10 167392.4 338339.8 -8.50082 54.2927 11 167946.9 337374.3 -8.4922 54.2841 12 165662.1 337278.7 -8.52727 54.2831 13 166057.4 338759.7 -8.52137 54.2964 14 165018.3 338818.4 -8.53734 54.2969 15 159843.2 340666.7 -8.61707 54.3131

Table 4-13: The classification of sediment particle size ranges into size classes (adapted from Buchanan, 1984)


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Range of Particle Size Classification Phi Unit

<63µm Silt/Clay >4 Ø

63-125 µm Very Fine Sand 4 Ø, 3.5 Ø

125-250 µm Fine Sand 3 Ø, 2.5 Ø

250-500 µm Medium Sand 2 Ø, 1.5 Ø

500-1000 µm Coarse Sand 1 Ø, 1.5 Ø

1000-2000 µm Very Coarse Sand 0 Ø, -0.5 Ø

>2000 µm Gravel -1 Ø, -1.5 Ø, -2 Ø, -3 Ø, -4 Ø

4.5.2.2. Data Processing

All replicates for each station were combined to give a total abundance for each

station prior to analyses. A data matrix of all the combined faunal abundance data

was compiled and used for statistical analyses. The faunal analysis was carried out

using the PRIMER ® (Plymouth Routines in Multivariate Ecological Research)

programme.

Univariate statistics in the form of diversity indices were calculated on the combined

replicate data. The following diversity indices were calculated:

1) Margalef’s species richness index (D), (Margalef, 1958).

D

S 1log2 N

where: N is the number of individuals

S is the number of species

2) Pielou’s Evenness index (J), (Pielou, 1977).

J =H' (observed)

Hmax'

where: H max'

is the maximum possible diversity, which could be achieved if all

species were equally abundant (= log2S)

3) Shannon-Wiener diversity index (H'), (Pielou, 1977).

H' = - pii=1

S(log2 pi )

where: pI is the proportion of the total count accounted for by the ith taxa

Species richness is a measure of the total number of species present for a given

number of individuals. Evenness is a measure of how evenly the individuals are

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distributed among different species. The diversity index incorporates both of these

parameters. Richness ranges from 0 (low richness) to 12 (high richness), evenness

ranges from 0 (low evenness) to 1 (high evenness), diversity ranges from 0 (low

diversity) to 5 (high diversity).

The PRIMER ® manual (Clarke & Warwick, 2001) was used to carry out multivariate

analyses on the station-by-station faunal data. It must be noted here that the species

that were present only once or twice in the survey were excluded from the

multivariate analysis. All species/abundance data were fourth root transformed and

used to prepare a Bray-Curtis similarity matrix in PRIMER ®. The fourth root

transformation was used in order to down-weigh the importance of the highly

abundant species and allow the mid-range and rarer species to play a part in the

similarity calculation. The similarity matrix was then used in classification/cluster

analysis. The aim of this analysis was to find “natural groupings’ of samples, i.e.

samples within a group that are more similar to each other, than they are similar to

samples in different groups (Clarke & Warwick, loc. cit.). The PRIMER ® programme

CLUSTER carried out this analysis by successively fusing the samples into groups

and the groups into larger clusters, beginning with the highest mutual similarities then

gradually reducing the similarity level at which groups are formed. The result is

represented graphically in a dendrogram, the x-axis representing the full set of

samples and the y-axis representing similarity levels at which two samples/groups

are said to have fused. The CLUSTER programme was set to include a series of

‘similarity profile’ (SIMPROF) permutation tests, which look for statistical evidence of

genuine clusters in samples which are a priori unstructured. SIMPROF performs

tests at every node of a completed dendrogram, that the group being sub-divided has

‘significant’ internal structure. The test results are displayed in a colour convention on

the dendrogram plot (samples connected by red lines cannot be significantly

differentiated).

The Bray-Curtis similarity matrix was also subjected to a non-metric multi-

dimensional scaling (MDS) algorithm (Kruskall & Wish, 1978), using the PRIMER ®

program MDS. This programme produces an ordination, which is a map of the

samples in two- or three-dimensions, whereby the placement of samples reflects the

similarity of their biological communities rather than their simple geographical

location (Clarke & Warwick, 2001). With regard to stress values, they give an

indication of how well the multi-dimensional similarity matrix is represented by the

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two-dimensional plot. They are calculated by comparing the interpoint distances in

the similarity matrix with the corresponding interpoint distances on the 2-d plot.

Perfect or near perfect matches are rare in field data, especially in the absence of a

single overriding forcing factor such as an organic enrichment gradient. Stress values

increase not only with the reducing dimensionality (lack of clear forcing structure), but

also with increasing quantity of data (it is a sum of the squares type regression

coefficient). Clarke and Warwick (loc. cit.) have provided a classification of the

reliability of MDS plots based on stress values, having compiled simulation studies of

stress value behaviour and archived empirical data. This classification generally

holds well for 2-d ordinations of the type used in this study. Their classification is

given below:

Stress value < 0.05: Excellent representation of the data with no

prospect of misinterpretation.

Stress value < 0.10: Good representation, no real prospect of

misinterpretation of overall structure, but very fine detail may be

misleading in compact subgroups.

Stress value < 0.20: This provides a useful 2-d picture, but detail

may be misinterpreted particularly nearing 0.20. Stress value 0.20

to 0.30: This should be viewed with scepticism, particularly in the

upper part of the range, and discarded for a small to moderate

number of points such as < 50.

Stress values > 0.30: The data points are close to being randomly

distributed in the 2-d ordination and not representative of the

underlying similarity matrix.

Each stress value must be interpreted both in terms of its absolute value and the

number of data points. In the case of this study, the moderate number of data points

indicates that the stress value can be interpreted more or less directly. While the

above classification is arbitrary, it does provide a framework that has proved effective

in this type of analysis.

SIMPER analysis was then carried out on the transformed data to determine the

dominant/characterising species within each group identified by the

CLUSTER/SIMPROF analysis.

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4.5.2.3. Results

4.5.2.3.1. Fauna

The taxonomic identification of the benthic infauna across all 15 stations sampled in

Sligo Harbour yielded a total count of 110 species accounting for 2,303 individuals,

ascribed to 8 phyla. A complete listing of these species abundance is provided in

Appendix C.

Of the 110 species enumerated, 43 were annelida (segmented worms), 29 were

crustaceans (crabs, shrimps, prawns), 32 were molluscs (mussels, cockles, snails

etc.), 2 species were arthropods (insects, spiders), 1 species was a nematode (round

worm), 1 was a nemertean (ribbon worm), 1 was a chelicerata (sea spider) and 1

species was a plathyhelminth (flatworm).

4.5.2.3.1.1. UNIVARIATE ANALYSES

Univariate statistical analyses were carried out on the combined replicate station-by-

station faunal data. The following parameters were calculated and can be seen in

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Table 4-14; species numbers, number of individuals, richness, evenness and

diversity. Species numbers ranged from 2 (Stations 5 and 15) to 35 (Station 1).

Number of individuals ranged from 2 (Station 5) to 1073 (Station 7). Richness ranged

from 0.25 (Station 15) to 6.97 (Station 4). Evenness ranged from 0.1 (Station 7) to

1.00 (Stations 5 and 10). Diversity ranged from 0.13 (Station 15) to 4.39 (Station 4).

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Table 4-14: Diversity indices for the 15 stations sampled in Sligo Harbour.

Station Species Individuals Richness Evenness Diversity 1 35 139 6.89 0.84 4.29 2 5 11 1.67 0.86 2.00 3 28 320 4.68 0.54 2.58 4 31 74 6.97 0.89 4.39 5 2 2 1.44 1.00 1.00 6 11 170 1.95 0.39 1.36 7 8 1073 1.00 0.10 0.29 8 5 21 1.31 0.63 1.47 9 32 184 5.94 0.74 3.68

10 6 6 2.79 1.00 2.58 11 3 4 1.44 0.95 1.50 12 14 169 2.53 0.52 1.99 13 7 24 1.89 0.79 2.21 14 7 50 1.53 0.45 1.26 15 2 56 0.25 0.13 0.13

4.5.2.3.1.2. MULTIVARIATE ANALYSES

The dendrogram and the MDS plot can be seen in Figure 36 and Figure 37

respectively. Five groupings were identified through the SIMPROF programme.

These are as follows:

Group a: Stations 1, 3, 6, 7, 9, 11 and 12

Group b: Stations 2, 5 and 10

Group c: Station 15

Group d: Station 4; and

Group e: Stations 8, 13 and 14.

Groups b and e consisted of sandy stations located within or close to the navigation

channel in the harbour. Group a consisted of sand, gravelly muddy sand, sandy

gravel and slightly gravelly muddy sand stations and all were located within the

harbor area. Stations 4 (slightly gravelly sand) and station 15 (no granulometric data)

were located outside the harbor and grouped separately from all the other stations.

Group a formed at a similarity level of 12.5%. The 7 stations in this group accounted

for 80 different species comprising 2,059 individuals. Of the 80 species present, 37

were present more than twice. Five species accounted for 80% of the abundance in

this group: the gastropod mollusc Hydrobia ulvae (1,326 individuals; 64.4%), the

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oligochaete Tubificoides benedii (162 individuals; 7.9%), the bivalve mollusc

Parvicardium pinnulatum (3 individuals; 3.6%), the barnacle Balanus crenatus (65

individuals; 3.2%) and the oligochaete Tubificoides pseudogaster agg. (31

individuals; 1.5%). This group had an average within group similarity of 21.33%

according to SIMPER analysis (See Table 4-15).

Group b formed at a similarity level of 50.36%. The 3 stations in this group accounted

for 8 different species comprising 19 individuals. Of the 8 species present, 3 were

present more than twice. Three species accounted for 74% of the abundance in this

group: the polychaete Scoloplos armiger (6 individuals; 32%); the bivalve mollusc

Tellina sp. (5 individuals; 26%) and the polychaete Eteone longa agg. (3 individuals;

16%). This group had an average within group similarity of 50.61% according to

SIMPER analysis (See Table 4-15).

Group c consisted of station 15 only. This station contained 2 species and 56

individuals. The bivalve mollusc Donax vittatus accounted for 55 of the individuals

(98% of the abundance). Within group similarity could not be calculated for this group

because it only contained 1 station.

Group d consisted of station 4 only. This station contained 31 species and 74

individuals. Of the 31 species present, 14 were present more than twice. The bivalve

mollusc Donax vittatus was also the dominant species at this station but in

significantly lower numbers than at station 15 (Group c). Four species accounted for

46% of the abundance in this group: Donax vittatus (12 individuals; 16%), the

polychaetes Nephtys cirrosa (9 individuals; 12%) and Scoloplos armiger (7

individuals; 9%) and the bivalve mollusc Tellina sp. (6 individuals; 8%). Within group

similarity could not be calculated for this group because it only contained 1 station.

Group e formed at a similarity level of 49.22%. The 3 stations in this group accounted

for 12 different species comprising 95 individuals. Of the 12 species present, 4 were

present more than twice. These four species accounted for 88% of the faunal

abundance: the bvivalve mollusc Tellina tenuis (64 individuals; 67%), the polychaete

Nephtys cirrosa (13 individuals; 14%) and the molluscs Retusa obtusa (4 individuals;

4%) and Mytilidae sp. (3 individuals; 3%). This group had an average within group

similarity of 55.88% according to SIMPER analysis (see Table 4-15). Table 4-15 also

shows the characterizing species for each group.

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These delineations were also preserved in the MDS plot. The stress value of the

MDS ordination is 0.1; which results in a good representation with no real prospect of

misinterpretation of the overall structure, but the very fine detail may be misleading in

compact subgroups.

Figure 36: Dendrogram showing the natural grouping of each station sampled in Sligo Harbour.

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Figure 37: MDS ordination showing the natural grouping of each station sampled in Sligo Harbour.

Table 4-15: SIMPER Results

Group A Average similarity: 21.33Species Av.Abund Av.Sim Sim/SD Contrib% Cum.%Hydrobia ulvae 2.23 3.99 0.76 18.69 18.69Tubificoides benedii 1.34 3.04 0.79 14.23 32.92Cardiidae sp. (juv) 0.95 2.62 0.79 12.3 45.22Tubificoides pseudogaster agg 1.08 2.09 0.87 9.79 55.01Parvicardium pinnulatum 1.03 1.55 0.49 7.27 62.27Pygospio elegans 0.86 1.39 0.58 6.51 68.78Capitella sp. 0.67 1.08 0.59 5.06 73.85Macoma balthica 0.6 1.03 0.59 4.84 78.69Cerastoderma edule 0.69 0.83 0.6 3.9 82.59Eteone longa aggregate 0.64 0.56 0.39 2.62 85.21Abra alba 0.29 0.49 0.22 2.32 87.53Aoridae sp. 0.51 0.42 0.39 1.99 89.51Platynereis dumerilii 0.57 0.34 0.4 1.59 91.11Group B Average similarity: 50.61Species Av.Abund Av.Sim Sim/SD Contrib% Cum.%Eteone longa aggregate 1 22.49 4.65 44.43 44.43Scoloplos armiger 1.14 22.49 4.65 44.43 88.86Tellina sp. (juv) 0.8 5.64 0.58 11.14 100Group D Less than 2 samples in group

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Group E Average similarity: 55.88Species Av.Abund Av.Sim Sim/SD Contrib% Cum.%Tellina tenuis 2.09 23.42 10 41.91 41.91Nephtys cirrosa 1.41 15.73 6.23 28.16 70.07Mytilidae sp. (juv) 1 12.41 11.19 22.22 92.28Group C Less than 2 samples in group

4.5.2.3.2. Sediment

The results from the traditional granulometric analysis can be seen in Table 3-5.

Figure 40 shows these data in graphical form. The sediment sampled during the

survey was classified as sand, slightly gravelly sand, sandy gravel, slightly gravelly

muddy sand and gravelly muddy sand according to Folk (1954). Figure 41 shows the

sediment type according to Folk’s (1954) classification.

The majority of stations were classified as sand (Stations 2, 3, 5, 7, 8, 10, 12, 13 and

4) (See Figures 34 and 35). All of the stations sampled within the harbour area (i.e.

inside Oyster Island) were classified as sand with the exception of the two inner

stations (stations 11 and 6) and station 1 located approximately 300m northeast of

Oyster Island. Station 1 was classified as sandy gravel, station 6 as slightly gravelly

muddy sand and station 11 as gravelly muddy sand. Outside the harbour area,

station 4 was classified as slightly gravelly sand.

Station 1 contained the highest percentage of gravel (68.5%). Station 9 contained the

highest percentage of very coarse sand (10.2%) and coarse sand (8.3%). Station 14

contained the highest medium sand fraction (33.5%). Station 12 contained the

highest fine sand (89.3%). Station 2 contained the highest very fine sand (15.6%)

and station 11 contained the highest silt-clay (16.8%).

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Table 4-16: Granulometry results for the 16 stations sampled in Sligo Harbour (as percentage weight of the total sample).

Station Gravel (%)

Very Coarse Sand(%)

Coarse Sand(%)

Medium Sand (%)

Fine Sand(%)

Very Fine Sand (%)

Silt-Clay (%)

Folk (1954)

1 68.5 7.7 4.6 4 9.5 4.9 0.9 Sandy gravel

2 0.7 1.1 1.7 4.8 75 15.6 1 Sand

3 0.2 0.3 0.5 2.7 81.7 9.3 5.2 Sand

4 3.4 1.4 2.3 8.1 81.7 3.1 0.1 Slightly gravelly sand

5 0.5 0.6 1.5 3.8 77.3 14.1 2.1 Sand

6 1.3 1.4 1.5 3.6 58.4 20.9 13 Slightly gravelly muddy sand

7 0.1 0.3 0.4 6.1 85.3 7.2 0.5 Sand

8 0.8 2.4 6.4 26.8 60.2 3.2 0.1 Sand

9 51 10.2 8.3 9.8 15.4 4 1.2 Sandy gravel

10 0 0.1 0.3 5.1 89.2 5.3 0 Sand

11 6.8 2.9 2 3.1 46.5 22 16.8 Gravelly muddy sand

12 0.2 0.3 0.6 3.3 89.3 5.8 0.5 Sand

13 0.2 1.7 3.3 13.4 79.5 1.8 0 Sand

14 0.6 1.8 5.4 33.5 56.5 2.2 0 Sand

*The particle size ranges for each classification (gravel, very coarse sand, coarse

sand, medium sand, fine sand, very fine sand and silt clay) is adapted from

Buchanan, 1984 and can be seen in Table 4-13. The classifications according to Folk

(1954) are based on varying percentages of gravel, sand and silt-clay.

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Figure 38: Sediment grain size data

Figure 39: Sediment type according to Folk (1954)



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4.5.2.3.3. Organic carbon

Sediment samples were taken for organic carbon analysis. Samples were sent to

SAL (Scientific Analysis Laboratories, Manchester, England – a UKAS and UK

Environment Agency MCERTS accredited laboratory) for total organic Carbon (TOC)

determination.

Station

Determinand Units

RPS 1

RPS 2

RPS 3

RPS 4

RPS 5

RPS 6

RPS 7

RPS 8

RPS 9

RPS 10

RPS 11

RPS 12

RPS 13

RPS 14

TOC % 2.0 2.1 1.5 0.3 1.6 3.8 1.6 1.7 3.1 2.6 5.2 1.5 1.1 1.6

Table 4-17: Sediment granulometry and organic carbon results for the fourteen stations surveyed off Sligo, 06th October, 2010.

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5. Assessment of Likely Effects

Impact assessment has been undertaken with due regard to the EPA “Advice Notes

on Current Practice” (2003); the EPA “Guidelines on the information to be contained

in Environmental Impact Statements” (2003); with reference to the discipline-specific

Institute of Ecology and Environmental Management’s “Guidelines for Ecological

Impact Assessment” (IEEM, 2006) and the National Roads Authority’s “Guidelines

(NRA), for Ecological Impact Assessment”.

Criteria for assessing impact level have been derived from those set out in Appendix

4 of the NRA discipline specific EcIA Guidelines (2004), but expanded in order to be

able to address issues such as habitat quality and are shown in Appendix E of this

report. Terminology for impact significance and duration follows that set out by the

EPA (2003) in its generic guidelines.

5.1. Consideration of significance

In terms of significance, the NPWS Guidance (2010 Rev) uses an EC definition as

follows:..”any element of a plan or project that has the potential to affect the

conservation objectives of a Natura 2000 site, including its structure and function,

should be considered significant (EC, 2006)”. Other guidance documents also

discuss significance criteria, some in more detail than others. The Dutch Guidance4

(2004) discusses a number of criteria in relation to habitats and species population.

In general, significance indicators might include:

impact on Annex I habitat (including loss or reduction in size - percentage

relative to the overall area of the habitat in the Natura site; impairment of

function);

fragmentation of habitat or population (depending upon the duration or

permanence);

disturbance (noise, light etc. - distance, duration);

4 Translated from Publication of Dutch State Printers in book:’Praktijkboek Habitattoets’ , 2004 (F. Neumann en H.

Woldendorp, SDU)

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effect on species populations (direct or indirect damage to size, breeding

patterns etc);

changes in water quality.

To summarise the significance issue, it is useful to quote from Morris (2008) who

describes significance in the context of the Habitats Directive as follows: “...Within the

Habitats Regulations, significance is quite different. It is used as a coarse filter and

the test is a question over the possibility that there will be a significant effect on a key

receptor that determines the conservation status of a European site. Thus,

determining whether there will be a ‘likely significant effect’ does not imply that there

will be such an effect or even that such an effect is more likely than not; it simply

flags the need to test the issues and then make a judgement of the pathways and

mechanisms imposed by a project on the designated wildlife interest. This test best

equates to the screening and scoping opinions sought for an EIA but is confined to

the Natura 2000 and Ramsar interest rather than wider environmental or nature

conservation issues”.

In order to assess the likely impacts and ascertain whether a significant impact on

the integrity of the Natura site(s) is likely to occur as a result of the proposed

development, should the appropriate assessment process deemed to be required, it

is necessary to consider what constitutes the integrity of a Site as referred to in

Article 6(3). The document Managing Natura 2000 Site, The provisions of Article 6 of

the ‘Habitats’ Directive 92/43/EEC (2000) gives clear guidance in this regard and

states: “The integrity of the site involves its ecological functions. The decision as to

whether it is adversely affected should focus on and be limited to the site’s

conservation objectives”.

Integrity has been discussed and defined in various ways in guidance documentation

and the literature. For example, Treweek (1999) discusses biological integrity and

ecosystem health, and refers to three generally accepted criteria: systematic

indicators of ecosystem functional and structural integrity; ecological sustainability or

resilience (relating to the ability of a system to withstand “natural” or anthropogenic

stresses); and absence of detectable symptoms of ecosystem disease or stress. A

similar, but less academic, approach is adopted by the various guidance documents

with a number of definitions proposed. The essence of the concept of ecological

integrity is distilled in the following definition from Planning Policy Statement 9 (UK

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Department of Environment, 1994 – now superseded by PP9, 2005): “coherence of

the site’s ecological structure and function, across its whole area, or the habitats,

complex of habitats and/or populations of species for which the site is or will be

classified”.

5.2. Potential Impacts on Natura 2000 sites – Impacts Prediction

Criteria for assessing impact level have been derived from those set out in Appendix

4 of the NRA EcIA Guidelines (2004) criteria and expanded in order to be able to

address issues such as habitat quality. Terminology for impact significance and

duration follows that set out by the EPA (2003). The potential impact magnitude

described in the following sections, without mitigation, is negative unless otherwise

stated as being positive or neutral. Where the impact is stated as being localised, it

refers to the immediate area of impact.

Impacts on habitat and species (Marine Ecology) for the Natura sites are

summarised in Table 5-4 at the end of Section 5.

5.2.1. Potential impacts on Cummeen Strand/Drumcliff Bay SAC

5.2.1.1. Potential impacts on habitats in Cummeen Strand/Drumcliff Bay SAC

5.2.1.1.1. Qualifying marine habitats for the Cummeen Strand/Drumcliff Bay SAC

The proposed dredging scheme will have a direct impact on the Mudflats and Sand

flats/Estuarine habitats in Sligo Harbour (see Table 4-3). This impact may be divided

into two parts:

The removal [by dredging] of sediments from the estuarine environment

The suspension of sediments in the water column as a result of the dredging

operation and the subsequent deposition of some of this material over parts

of the mudflats and sandflats in Sligo Harbour

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5.2.1.1.1.1. The removal of estuarine sediments

There will be a loss of benthic habitat along the navigational channel as a result of

sediment removal. Along the channel where dredging occurs, removal of all surface

sediment and associated fauna will occur over a relatively short time frame. The

dredging footprint (as shown in Figure 2 on Page 11 of this NIS) extends across an

area of up to 271,910m², which is 0.56% of the SAC area (48,562,179m²).

5.2.1.1.1.2. Deposition of sediments on mudflats and sandflats

Based on the results of the hydrodynamic sediment transport model attached in

Appendix F, during the proposed dredging operations, sediment put into suspension

by the dredger during water injection dredging will be dispersed around the northern

portion of Sligo Harbour. The sediment will be redistributed during periods of higher

current velocities during successive spring tides, before eventually coming to rest in

small deposits around the fringes of Sligo Harbour and Cartron Marsh (see Figure 8in

Appendix F). Some of the material will be successfully transported out of the harbour

and will settle out on the nearby sand banks in depths of a few mm.

During conventional dredging small amounts of sediment put in to suspension by the

dredger will be temporarily deposited along the sides of the navigation channel and in

sheltered areas along the north shore of the harbour area.

The areas that will experience the greatest amount of temporary sedimentation occur

along the north shoreline of Sligo Harbour (peak sedimentation during dredging of

20-70mm). It should be noted that these peak values are typically of a short duration

(a matter of hours) and tend to occur during slack tide. The material may then be re-

suspended and transported elsewhere as the tidal currents pick up during the

subsequent tide. The residual pattern of sedimentation following completion of all

conventional dredging operations is shown in Figure 11.29 in Appendix F. This

shows that the maximum final deposition depth following completion of operations

does not exceed 1mm in the majority of the harbour area and exceeds 25mm only in

very localised areas around the navigation channel and the northern shore of the

harbour.

Post dredging, the modelled area in which there will be residual deposits of sediment

in excess of 25mm is approximately 35,078m². These deposits will be mainly

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concentrated in the lee of the training wall. The area of habitat which will experience

residual deposition in excess of 25mm represents approximately 0.18% of the SAC

habitat “Mudflats and sandflats not covered by seawater at low tide” or 0.07% of the

overall SAC area.

5.2.1.2. Potential impacts on qualifying species and listed species for the Cummeen

Strand/Drumcliff Bay SAC

Once dredging ceases, recovery of the dredged area will follow. In a harbour

navigation channel where both maintenance and capital dredging is routinely carried

out, this cycle of regular disturbance and subsequent recovery has played out as

long as the channel has existed and will continue to do so for as long as the channel

is maintained and used. The benthic environment surrounding the Sligo Harbour

navigation channel exists in its current form after a long history of similar periodic

disturbance. The typical phases of recovery following dredge disturbance are

outlined below.

Recovery begins with the colonisation of the defaunated area by small opportunistic

species adapted to survive in areas of physical disturbance. This colonisation occurs

either from neighbouring sites or via larval settlement or both. Few organisms follow

this life style strategy so there is a tendency for a limited number of species to reach

extremely high densities in the presence of pollutants. The bioturbatory activities of

these infauna start to significantly modify the physical, chemical and biological nature

of the deposit. The macrofaunal assemblage enters a ‘transitory’ phase of

succession when the sedimentary changes allow further colonisation of a larger

variety of species. This stage is unfavourable for the ‘pioneer’ population to persist.

Species that characterise the transitory sere include suspension and deposit feeding

bivalves, ‘conveyor belt’ polychaetes and relatively immobile holothurians. Here

again the physical and chemical properties of the sediment are further modified by

the new infaunal dominants making way for additional species to take hold. A more

complicated and persistent faunal assemblage now forms and evolves towards an

‘equilibrium’ or ‘climax’ community status

What is described above is typical of recovery from a physical disturbance like

dredging. This recovery sequence is applicable if there is no subsequent disturbance

to the site. While there will be a temporary loss of infaunal habitat due to the removal

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of sediment from an area of up to 271,910m² (which is 0.56% of the SAC area),

recolonisation of denuded habitat will occur quickly and the floral and faunal

communities inhabiting the qualifying habitats in the SAC will not be permanently

impacted.

5.2.1.2.1. Qualifying plant species for the SAC

No qualifying marine plant species listed for this SAC.

5.2.1.2.2. Listed bird species for the SAC – Annex I species (EU Birds

Directive)

Table 4-4 on page 21 lists the Annex I Birds Directive species listed on the standard

data form for the SAC/SPA. These are Golden Plover, Bar-tailed Godwit, Chough

and Barnacle Goose.

5.2.1.2.3. Mammal species for the SAC – Annex II species (EU Habitats

Directive)

Based on the results of the desk study and field studies undertaken for the

Environmental Appraisal (summarised in Section 4.4 of this report) common seal are

not regularly recorded in Cummeen Strand/Sligo Harbour, Grey seal are even less

frequently recorded. Although their range does extend into Sligo Harbour, these

animals tend to occupy the more exposed portions of the bays to the north and south

of Sligo Harbour. No impact on these species is expected.

5.2.1.2.4. Qualifying Annex II and listed fish species for the SAC

Both the river lamprey (Lampetra fluviatilis) and the sea lamprey (Petromyzon

marinus) are listed for the Cummeen Strand/Drumcliff Bay SAC. These two species

both spawn in rivers and both occur in coastal and estuarine environments – though

L. fluviatilis tends to remain closer to the coast than P. marinus.” Additional detail on

lamprey migration is presented in Appendix G.

On migrating through estuarine environments these species may frequently

encounter high suspended sediment loads, which do not appear to impact on

migrations.

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Projected mean levels of suspended sediment during dredging operations are within

recommended guidelines and will not have an adverse effect the upstream and

downstream migrations of eels and lamprey.

5.2.1.2.5. Annex (II and IV) species not listed as qualifying or of special

interest for the SAC

5.2.1.2.5.1. Fish (Annex II)

The adjoining Lough Gill SAC (Site Code: 001976) is of considerable importance for

the presence of four Red Data Book fish species that are listed on Annex II of the

E.U. Habitats Directive - Brook Lamprey (Lampetra planeri), River Lamprey

(Lampetra fluviatilis), Sea Lamprey (Petromyzon marinus) and Atlantic Salmon

(Salmo salar).

It is likely that the three migratory species of the above – salmon and river and sea

lamprey – use the Sligo Harbour navigation channel during migrations to and from

the Lough Gill SAC.

More detailed information on salmonids is presented Appendix G.

Fish migrating through estuarine environments may frequently encounter high

suspended sediment loads which do not appear to impede this behavioural activity.

Atlantic salmon are known to move through the Severn Estuary where sediment

concentrations in suspension can reach into several thousand mg/l for periods

(Gibson, 1933). Simenstad (1988) suggests that salmonids are likely to have adapted

physiologically to the turbid conditions that occur naturally within estuarine and

harbour areas.

Suspended sediment concentrations in the lower 0.5m of water column are predicted

to remain relatively low throughout dredging operations. Adult salmonids are most

likely to move upstream via the navigation channel where the mean concentration will

be slightly higher (60mg/l) than the Fish Directive recommended limit of 25 mg/l for

salmonid waters for a period of a few days during the water injection dredging.

During the longer period of conventional dredging the mean suspended sediment

concentrations throughout this time will be slightly higher than background, but will

remain within the Fish Directive recommended limit of 25 mg/l for salmonid waters.

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Moreover, for all dredging activities suspended sediment concentrations are likely to

be lower closer to the surface of the water column, which salmon more commonly

utilise when swimming through estuarine and coastal waters.

Projected levels of suspended sediment are within recommended guidelines and will

not have an adverse effect the upstream and downstream migration of salmonids.

5.2.1.2.5.2. Otter (Lutra lutra) (Annex II and IV)

Otter are listed in the conservation objectives for the adjoining Lough Gill SAC.

Though not listed, this species also occurs in the Cummeen Strand/Drumcliff Bay

SAC. The proposed dredging scheme will not have an effect on the type of substrate

primarily used by otters for foraging i.e. the littoral and shallow sublittoral zones. Due

to the adaptability and mobility of this species, it is unlikely that the intermittent

temporary dredging works will have a significant negative effect on these animals.

5.2.1.2.5.3. Marine mammals (Annex II and Annex IV)

No cetaceans are listed as qualifying species for the Cummeen Strand/Sligo Harbour

SAC, or as being of special importance to the SAC. The dolphins and harbour

porpoises recorded in the Cummeen Strand/Sligo Harbour SAC are highly mobile

species. Due to the shallow depths that characterise this area it is likely that they

use this site primarily at high water. They are able to detect noise and vibration at

great distances and are unlikely to be impacted by either a plume of suspended

sediment (as they rely primarily on hearing, as opposed to vision for navigation) or

the physical presence and activity of a dredger. As they are air-breathing mammals,

the presence of an elevated level of suspended matter in the water column is of no

consequence to these species.

While harbour porpoises and dolphins visit Sligo Harbour on an infrequent basis, they

are not resident within this area. Dredging and disposal operations will not deter them

from entering the harbour and as they are mobile they can leave the site if

environmental conditions turn unfavourable. Larger Odontocetes and Mysticetes

have not been recorded in this area. The proposed dredging works will have a

negligible effect on cetaceans, provided correct management and communication

procedures are followed. It is recommended in the Environmental Appraisal that a

trained and experienced Marine Mammal Observer (MMO) should be put in place

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during dredging and dumping operations. The MMO will scan the surrounding area

to ensure no marine mammals are in a pre-determined exclusion zone in the 30

minute period prior to the commencement of any dredging operations. Operations

should cease temporarily if a cetacean or seal is observed swimming in the

immediate (<50m) area of industrial activity. Work can be resumed once the

animal(s) have moved away.

5.2.1.3. Other fish species

Due to their mobility, impacts to fish species occurring subtidally in the Cummeen

Strand/Sligo Bay SAC are likely to be negative, slight and short-term. Fish are very

sensitive to vibration and disturbance in the water column and quickly relocate when

disturbed. It is likely that demersal and pelagic fish species that become acclimatised

to the dredging pattern will learn to avoid the dredge plume (relocating upstream of

the tidal flow) and will enter the dredged area to scavenge on exposed, dead or

moribund infauna left behind on the seafloor in the wake of the dredging operation

(when dredging ceases as low tide is approaching). It is not uncommon that elevated

numbers of scavenging fauna are noted in areas where the seafloor has been

subject to physical disruption/disturbance.

Having undergone a sharp decline in recruitment from 1980, European eel (Anguilla

anguilla) is now listed as CR – critically endangered on the IUCN (International Union

for Conservation of Nature) Red Data List. A population of eel exists in Lough Gill

and it is likely that they use the navigation channel area during migrations to and

from their distant breeding grounds. All possible measures should be taken to

minimise disturbance to this species during migration through the estuarine

environment as the next classification level in the IUCN Red Data List is EW – extinct

in the wild. On migrating through estuarine environments eels may frequently

encounter high suspended sediment loads which do not appear to impact on

migrations.

Projected levels of suspended sediment during dredging operations are within

recommended guidelines and will not have an adverse effect the upstream and

downstream migrations of eels.

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5.2.2. Potential impacts on Cummeen Strand SPA

5.2.2.1. Potential impacts on the SPA qualifying and listed bird species of interest

Disturbance

There is potential for the disturbance of waterbirds as a result of noise, vibration and

dredging activity associated with the construction phase of the project. However,

waterbirds within Sligo Harbour/Cummeen Strand are unlikely to be significantly

disturbed by the dredging activities as the disturbance will be localised and short-

term in nature. The water injection dredging will only last for 3 days, with dredging

operations only taking place for around 4.5 hours per tidal cycle (approx 12.4 hours).

During conventional dredging operations, which may last up to 8 months, for each

tidal cycle the dredger will only be able to dredge for around 70-80 minutes. The rest

of the time it will be travelling to and from the proposed dump site (approximately

50km away, offshore). A typical dredger would travel at an average speed of 6.5

knots laden and 8 knots unladen, therefore taking around 10 hours in normal

conditions to for a return trip to the dump site, including the time taken to discharge

the sediments.

Bird species in the harbour are already subject to disturbance from recreation,

transport (shipping movements in the harbour and low flying aircraft in the area of

Sligo Airport) and other activities and appear to be habituated to current levels of

disturbance.

Given the factors discussed above, disturbance to waterbird species as a result of

the proposed dredging activities (either alone or in combination with existing

disturbance levels) will result in an imperceptible impact. It is extremely unlikely to

have a significant negative effect on waterbirds within Sligo Harbour/Cummeen

Strand, even in the short term.

Direct loss of habitat

The proposed works will require the removal of predominantly sub-tidal substrate

within the existing deep water channel in Sligo Harbour. However, the proposed

works will also require the removal of a small area (c. 31,811m² or 0.07% of the

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overall cSAC area5) of intertidal material (fine sand and silts) inside the training wall

between Ballyweelin Point and the Deepwater Jetty. A total estimated volume of

250,000m3 of sediment will be removed from the estuarine environment in Sligo

Harbour during the course of the proposed work. This material will be removed from

an area that has been the subject of previous large scale dredging works (in 1998)

and exists as a maintained channel at this location, which is delineated by man-made

training walls at its outer edges. The removal of this material will not have a

significant negative effect on the estuary and will not destabilise the structure or

functioning of the estuary relative to existing conditions. From observations made

during the field surveys, the intertidal area between the training walls along the deep

water channel is not of great importance for birds within the estuary as a whole. The

volume of sediment to be removed is not significant in the context of the total

available sediment within the SPA and will not have any significant effect on the

habitats, or on the waterbirds, within the estuary. The training walls along the

shipping channel are an important roost site for waterbirds in Sligo Harbour.

However, the training walls will not be directly impacted by the proposed dredging

works.

A literature review was undertaken as part of this assessment to find any examples

of recorded impacts of dredging activity on estuarine birds elsewhere. An

assessment of potential impacts of both capital and maintenance dredging on birds in

the Tamar Estuary, south-west England was published (Widdows et al. 2007).

Maintenance dredging in the lower Tamar typically accounts for the annual removal

of between 5,000 and 200,000 tonnes of dry sediment per year. During periods of

capital dredging, the amount of sediment dredged increased significantly to between

500,000 and 700,000 tonnes per year. The study reviewed population data for ten

bird species, including mallard, shelduck, teal, wigeon, curlew, dunlin, oystercatcher

and redshank, over a 30-year period from 1971 to 2002. None of the wildfowl or

wader species studied showed any correlation between bird numbers and dredging

activity in the Tamar. There were no marked changes in numbers during the year of

peak dredging or during the following winters. Declines in teal and wigeon were

considered to be related to a series of milder winters reducing their need to migrate

as far as south-west England.

5 The area of the cSAC (48,541,373 m²) has been calculated using the geodatabase file of the Cummeen Strand/Drumcliff Bay (Sligo Bay) SAC polygon (v1.04) as published on the National Parks and Wildlife Service data maps viewer http://webgis.npws.ie/npwsviewer/ on 21 October 2012

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Given the factors discussed above, the removal of intertidal and sub-tidal material as

a result of the proposed dredging activities will result in a slight impact in the short-

term in the immediate area. However, the impact will reduce to an imperceptible

impact within a short period, particularly when taken in the context of the estuary as a

whole and the wider complex of estuarine habitats that make up Sligo Bay. It is

extremely unlikely to have a significant negative effect on waterbirds within Sligo

Harbour/Cummeen Strand, even in the short term.

5.2.2.2. Potential impacts on the macrobenthos - food source for SPA bird species

Intertidal macrobenthos is of greatest value to bird species as a food source (due to

accessibility). The subtidal infaunal macrobenthos along the floor of the navigation

channel will be subject to the greatest level of impact (complete removal, though with

potential for rapid recolonisation). Impacts to the intertidal macrobenthos are likely to

be imperceptible, localised and temporary, as the continued movement of the

dredger along the navigation channel will ensure that any given area will not be

impacted for a protracted period.

The hydrodynamic modelling presented in Appendix F shows that the sediment put

into suspension by the dredger during water injection dredging will be dispersed

around the northern portion of Sligo Harbour. The sediment will be redistributed

during periods of higher current velocities during successive spring tides, before

eventually coming to rest in small deposits around the fringes of Sligo Harbour and

Cartron Marsh (see Figure 8 in Appendix F). Some of the material will be

successfully transported out of the harbour and will settle out on the nearby sand

banks in depths of a few mm.

During subsequent conventional dredging, small amounts of sediment put in to

suspension by the dredger during dredging operations will be temporarily deposited

along the sides of the navigation channel and in sheltered areas along the north

shore of the harbour area.

The areas that will experience the greatest amount of temporary sedimentation occur

along the north shoreline of Sligo Harbour (peak sedimentation during dredging of

20-70mm). These peak values are typically of a short duration (a matter of hours)

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and the material may then be re-suspended and transported elsewhere as the tidal

currents pick up during the subsequent tide. The residual pattern of sedimentation

following completion of all conventional dredging operations is shown in Figure 11.29

in Appendix F. This shows that the maximum final deposition depth following

completion of operations does not exceed 1mm in the majority of the harbour area

and exceeds 25mm only in very localised areas around the navigation channel and

the northern shore of the harbour. Overall, the amount of sediment deposited in the

harbour area as a result of the dredging will be insignificant. No residual impact is

expected.

5.2.2.3. Noise impact on benthos

Impacts on benthos from noise in the vicinity of the dredging operation are expected

to be localised and temporary. The fact that the proposed dredging will take place in

an already busy port navigation channel suggests that the additional, temporary

noise loading of a dredger at work would be of minimal significance to benthos in the

vicinity of the dredged area.

5.2.2.4. Bivalve Beds

Blue mussels (Mytilus edulis) are filter-feeding bivalves that have a very high

efficiency in removing particulate matter (phytoplankton, organic matter and

suspended sediment) from the water column to an extent that food for the bivalves

may become a limiting resource at the sediment-water interface. This high efficiency

at removing particulate matter from the water column directly relates to the potentially

adverse effects of dredging-induced sediment plumes on these filter feeding bivalves.

Large quantities of suspended sediment in the water column can be detrimental due

to clogging of the gills and impairment of proper respiratory and excretory functioning

and feeding activity. Overall, research suggests that the degree of an impact on filter-

feeding species depends on the extent of turbidity and sedimentation against

background levels. Benthic shellfish in normally turbid environments (such as that

found in the Cummeen Strand area) are probably able to survive smothering unless

the rate of deposition is excessive. Studies also show that filter feeders, and bivalves

in particular, are highly adaptable in their response to increased suspended sediment

levels from, for example, periodic storms and dredging, maintaining their feeding

activities over a wide range of particulate loads and suspended sediment

concentrations (Newell et al., 1998).

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Previous studies on effects of suspended sediments on adult mussels (Mytilus

edulis) have shown that they are capable of coping with extreme high concentrations

of suspended material (Kiørboe et al., 1980). In one recent study, a no effects level of

1,867 mg/L for Mytilus edulis has been reported (Anchor Environmental, 2003). In

laboratory studies, lethal concentrations for adult bivalves exposed for as long as 3

weeks were in the realm of fluid mud, i.e. around 10,000 mg/L (Clarke & Wilbur,

2000). The ability for mussels to effectively utilize suspended food particles for

growth is optimal at concentrations below 50 mg/L. Concentrations above 100 mg/L

result in weight loss (Prins & Smaal, 1989). The growth rate of common mussels

increased in a field experiment in Denmark, where mussels were regularly exposed

to silt concentrations between 200-250 mg/L in a plume originating from dumping of

dredged spoil during a period of five weeks (Birklund & Wijsman, 2005). The high

concentrations did not affect the survival of the mussels. Mussels can protect

themselves from overloading by temporarily closing the valves and the closing

response depends on the size of the mussels. Widdows et al. (1979) demonstrated

that maximum filtering rates by 3cm long mussels (Mytilus edulis) (from an area that

had a natural range in suspended matter between 5 and 35 mg/L) were found at

suspended matter concentrations of 125mg/L, 30% reduced at 225mg/L and

negligible at concentrations >250 mg/L. Larger mussels (7 cm) stopped filtering and

closed their valves at 350 mg/L. When mussels are given sufficient time (months),

they can adapt their gills and palps to higher concentrations of suspended matter up

to concentrations as high as 400 mg/L (Essink et al., 1989).

Suspended bottom material, which is always present in the natural habitats of the

blue mussel Mytilus edulis, serves as an important additional food source for the

mussels. Mytilus edulis depends on this suspended bottom material to exploit fully its

clearance potential and reach the maximum growth rates observed in nature

(Kiørboe et al., 1980). Field research in the Ems Estuary (The Netherlands) indicated

that a 10-20% increase in turbidity did not have negative impacts on the growth and

survival of mussels (Essink et al., 1990).

In instances of incidental deposition, sessile benthic species such as mussels have a

relatively low tolerance of sediment cover. Adult mussels in a mussel bed are not

capable of moving upwards after deposition of layers of mud or sand and deposition

of a layer of 1-2cm within a relatively short period can be considered fatal to mussels

(Essink, 1999).

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Based on the above information, the tolerance thresholds of mussel beds is

summarised in Table 5-1.

Table 5-1: Summary of critical thresholds for mussel (Mytilus edulis) beds.

Species Parameter Optimum Range Maximum Tolerated

Mytilus

edulis

Suspended

sediment

<1867 mg/l

50-100 mg/l

<250 mg/l (5 weeks)

<400 mg/l (turbid estuaries)

<10,000 mg/l for 3 weeks

(adult)

Sedimentation 1-2 cm (within short time)

Impacts of the dredging plume on mussel beds in Sligo Harbour are considered

negligible. Mussels are very tolerant of extremely high turbidities (see Table 5-1).

The proposed dredging scheme will not have any impact on mussels (adults, larvae

or spat). Neither suspended sediment levels nor sedimentation rates as modelled in

Appendix F, “Hydrodynamic Modelling” reach lethal levels for mussels.

5.2.2.5. Zostera Beds

Light is one of the key environmental resources imperative for the growth and

survival of seagrasses (Hemminga & Duarte, 2000). The degree of water

transparency (which determines the depth-penetration of photosynthetically active

radiation of sunlight) is the primary factor determining the maximum depth at which

seagrasses can occur. Reduction in light due to turbidity has been identified as a

major cause of the loss of seagrasses worldwide (Shepherd et al., 1989; Green &

Short, 2003). The amount of light that reaches a seagrass leaf is determined by the

natural water colour, concentration of suspended solids, phytoplankton concentration

and the epiphyte cover of the leaf. There are various reports of sublethal and lethal

effects on seagrass meadows due to prolonged exposure to high turbidity and

siltation associated with dredging activities (Erftemeijer & Lewis, 2006). Laboratory

experiments have shown that some seagrasses can survive in light intensities below

their minimum requirements for periods ranging from 4 weeks to several months.

However, widespread seagrass mortality was observed in Chesapeake Bay (USA)

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following a month-long (seasonal) pulse of increased turbidity (light extinction

coefficient (k)>3.0 m-1) (Moore et al., 1997).

The minimum light requirements of Zostera marina (eelgrass) have been extensively

studied in a range of locations and environments. The values for the minimum light

requirements of this species, as reported in literature, vary between 11 and 37 % of

Surface Irradiance (SI). For the survival of seagrasses, the lowest value of 11%SI is

the most critical level below which widespread mortality surely occurs. Some of the

higher values (up to 37%SI) reported for eelgrass appear to refer to the minimum

light levels required to enable and sustain lateral shoot development, meadow

expansion and flowering. Levels below 37%SI but above 11%SI do affect these

processes, but may not cause substantial eelgrass mortality. There has been only 1

detailed study of the minimum light requirements for Zostera noltii: Peralta et al.

(2002) reported a minimum light requirement of 2% of SI for Zostera noltii in Spain.

According to the same study (also reported in: MarLIN Database, 2006), Zostera

noltii plants can tolerate acute light reduction below 2% SI for up to two weeks, and

thus appear tolerant of short-term events of very high turbidity. A recent monitoring

study into the effects of a dredging plume on intertidal eelgrass (Zostera marina) in

the Ems Estuary (The Netherlands) during (day-time) periods of low tide exposure

(Ochieng & Erftemeijer, 2009). This implies that intertidal eelgrass plants are

relatively tolerant to further turbidity increases such as may be caused by a dredging

plume (Ochieng and Erftemeijer, 2009). Based on the above information, the

tolerance thresholds of seagrass beds to turbidity is summarised in Table 5-2.

Table 5-2: Tolerance thresholds of Zostera spp. to turbidity levels.

Seagrass Species Minimum Tolerated Optimum Range

Zostera marina 11-37% SI >37% SI

Zostera noltii 2% SI can tolerate acute light reduction

below 2% SI for 2 weeks

Several studies have documented deterioration of seagrass meadows by smothering

due to excessive sedimentation (Erftemeijer and Lewis, 2006). Seagrass species that

develop vertical shoots may respond to fluctuations in sediment depth by modifying

their vertical growth but there are limits to the level of sedimentation seagrasses can

tolerate. Sedimentation rates of as much as 1013 cm yr-1 have been reported as

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maximum threshold of what some seagrass species can survive. Settlement of

suspended material on leaf blades of seagrasses may interfere significantly with

photosynthesis, and appears especially significant in low wave energy environments

where fine sediments are present and can settle out. A maximum allowable

sedimentation rate of 2 cm in 4 months was reported for Mediterranean Zostera noltii

(Spain). Tolerance of Zostera noltii in the Dutch Wadden Sea was documented to

range from minor erosion of 2 cmyr-1 to maximum sedimentation levels of 25 cm yr-1.

Mortality of 75% was reported for Zostera marina meadows (USA) at burial with 4 cm

(i.e. 25% of plant height), which demonstrates that this species is probably more

sensitive to sedimentation than some of the other (taller) seagrass species. Vermaat

et al. (1997) proposed an estimate of the annual sedimentation rates that can be

survived or escaped by seagrasses, either vertically or horizontally, to be in the order

of 5-10 cm yr-1. Based on the above information, the tolerance thresholds of seagrass

beds to sedimentation is summarised in Table 5-3.

Table 5-3: Tolerance thresholds for Zostera spp. to sedimentation.

Seagrass Species Minimum Tolerated Maximum Tolerated

Zostera marina 75% mortality at 4cm/day (25%

of plant height

Zostera noltii -1 to -2 cm/yr (erosion) 2-5 cm/year (sedimentation)

2cm / 4 months

Impacts of the dredging plume on the seagrass beds in Sligo Harbour are considered

negligible, because the plumes of high turbidity and sedimentation do not reach the

seagrass beds documented in the area. Besides, intertidal seagrass is probably not

affected much by increased turbidity anyway, since it obtains most of its light during

(day-time) periods of low tide exposure (see Ochieng & Erftemeijer, 2009). Based on

the final sediment deposition depth computed for the Cummeen Strand seagrass

habitat, on completion of all dredging activities, no residual impact on this habitat is

expected.

5.2.3. Indirect Impacts on Natura sites in the wider locality, including Lough Gill SAC

The adjoining Lough Gill SAC (Site Code: 001976) is of considerable importance for

the presence of four Red Data Book fish species that are listed on Annex II of the

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E.U. Habitats Directive - Brook Lamprey (Lampetra planeri), River Lamprey

(Lampetra fluviatilis), Sea Lamprey (Petromyzon marinus) and Atlantic Salmon

(Salmo salar). It is likely that the three migratory species of these, salmon and river

and sea lamprey, use the navigation channel during migrations between the sea and

the Lough Gill SAC. Timing of the works should take these migrations into account

and, despite the fact that the Lough Gill SAC will not be directly impacted by the

proposed dredging works, the link between freshwater and seawater habitats and

species should not be ignored.

5.2.4. Cumulative Impacts

5.2.4.1. Introduction

In order to identify potential “In Combination Effects”, other plans and projects were

identified for this area.

Bird species in the harbour are already subject to disturbance from recreation,

transport (shipping movements in the harbour and low flying aircraft in the area of

Sligo Airport) and other activities and appear to be habituated to current levels of

disturbance.

The proposed installation of pumping station works at Rosses Point has been

considered in relation to a risk of impacts on Sligo Harbour.

The harbour authority may undertake the small scale emergency maintenance

dredging (c. 5,500m³) in the vicinity of the berths using the water injection dredging

technique some time ahead of the conventional dredging, if funding cannot be sought

for the entire project within an acceptable time frame. The time delay between the

two dredging episodes could be several years and therefore no cumulative effects

are anticipated.

5.2.4.2. Overall Cumulative Impact of All Projects

It is not considered likely that this project will have any significant “in combination”

effects with any other plans or projects on Cummeen Strand SPA and Cummeen

Strand/Drumcliff Bay SAC.

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Table 5-4: Summary of expected impacts on marine habitats and species in the Natura sites

Natura 2000 site Status of

Habitat/Species Habitat / or location / species

Potential during dredging/ potential following

dredging

Area of impacts on habitats

within the Natura site (m2)

Predicted short term impact (assuming the successful implementation of mitigation measures)

Predicted residual impact (assuming the

successful implementation of mitigation measures)

Cummeen

Strand/Drumcliff Bay

SAC (000627)

Annex I qualifying

habitats Mudflats and sandflats not covered by seawater at low

tide 1140

Sediment removal, habitat

loss, habitat disruption and

disturbance to faunal

species

c. 31,811m² Moderate negative

(in localised area)

Neutral or

imperceptible

negative

Sediment deposition c. 35,078m² Slight negative

Neutral or

imperceptible

negative

Estuaries 1130

Sediment removal, habitat

loss, habitat disruption and

disturbance to faunal

species

up to 271,910m² Moderate negative

(in localised area)

Neutral or

imperceptible

negative

Sediment deposition 0 Slight negative

Neutral or

imperceptible

negative

Qualifying plant

species Not applicable - - - -

Annex I bird species

Golden Plover

Bar-tailed Godwit

Chough

Barnacle Goose

Whooper Swan

Noise & human disturbance

Disturbance/removal of

intertidal habitat


subtidal habitat

Dispersion & settlement of

sediments on and subtidal

habitats

-

Moderate negative

reduce to a slight

and then

imperceptible impact

within a short period

Imperceptible

negative

Mammal species for

the SAC Annex II

Phoca vitulina 1365

Halichoerus grypus 1364

Neither regularly recorded in

Cummeen Strand/Sligo

Harbour. Possible

disturbance due to noise from

dredging

-

Neutral or

imperceptible

negative

None expected

Qualifying fish

species Annex II

Lampetra fluviatilis 1096


Disturbance during

migrations/feeding activities. -

Imperceptible to

slight negative

Neutral or

imperceptible

negative

SAC listed migratory

bird species

Northern Fulmar Fulmarus glacialisGreat Cormorant Phalacrocorax carboBrent Goose Branta berniclaCommon Shelduck Tadorna tadornaWigeon Anas penelopeTeal Anas creccaMallard Anas platyrhynchosCommon Merganser Mergus merganserOystercatcher Haematopus ostralegus Ringed Plover Charadrius hiaticulaGrey Plover Pluvialis squatarolaNorthern Lapwing Vanellus vanellusDunlin Calidris alpinaCurlew Numenius arquataRedshank Tringa totanusGreenshank Tringa nebularia



intertidal habitat


subtidal habitat


sediments on intertidal and

subtidal habitats

-

Moderate negative

reduce to a slight

and then



Imperceptible

negative

SAC species of

importance -

mammals

Not applicable - - - -

SAC species of

importance

amphibian

Not applicable - - - -

SAC species of

importance - reptile Not applicable - - - -

Annexed faunal

species (neither

qualifying nor listed

for the SAC)

Migratory fish inhabiting Lough Gill SAC, when present

(during migrations -see Lough Gill SAC impacts below) -

Otter - Lutra lutra 1355

(Annex II & IV)

Disturbance during dredging

work may affect the foraging

range of otters in the area.

Impact level: temporary to

short term, localised

Moderate negative

-

Potential for

localised Slight to

Moderate Negative

Neutral

Cummeen Strand

SPA (004035)

SPA qualifying and

listed bird species

Brent Goose Branta bernicla Shelduck Tadorna tadorna Wigeon Anas penelope Teal Anas crecca Mallard Anas platyrhynchos Red-breasted Merganser Mergus serrators Oystercatcher Haematopus ostralegus Ringed Plover Charadrius hiaticula Lapwing Vanellus vanellus Red Knot Calidris canutus Sanderling Calidris alba Dunlin Calidris alpina Curlew Numenius arquata Ruddy Turnstone Arenaria interpres Black-headed Gull Larus ridibundus Redshank Tringa totanus Greenshank Tringa nebularia Common Gull Larus canus



intertidal habitat


subtidal habitat


sediments on intertidal and

subtidal habitats

-

Moderate negative

reduce to a slight

and then



Imperceptible

negative

Species neither

qualifying nor listed

for the SPA

Macrobenthos – food source for SPA bird species Effects of sediment

deposition c. 35,078m² Slight negative

Neutral or

imperceptible

negative

Bivalve beds Effects of sediment

deposition 0m² Slight negative

Neutral or

imperceptible

negative

Seagrass Zostera sp. beds Effects of sediment

deposition <300m²

Imperceptible

negative

Neutral or

imperceptible

negative

Indirect impacts on Natura 2000 sites in the wider locality

Lough Gill SAC

(001976)

Qualifying fish

species (Annex II) Atlantic salmon - Salmo salar 1106

Disturbance during

migrations -

Imperceptible

negative

Imperceptible

negative

Other fish species

(IUCN Red Data

List CR Critically

Endangered)

European Eel - Anguilla anguillaDisturbance during

migrations -

Imperceptible

negative

Imperceptible

negative

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6. Mitigation measures

6.1. Habitats in Cummeen Strand/Drumcliff Bay SAC

6.1.1. The removal of estuarine sediments

If the proposed scheme to maintain the current navigation channel for shipping into

Sligo Harbour is to be realised, then 250,000m3 of sediment will be removed from this

area. The dredging footprint (as shown in Figure 2 on Page 11 of this report) extends

across an area of up to 271,910m², which is 0.56% of the SAC area (48,562,179m²).

If the Sligo Harbour entrance channel is to be maintained as a navigable shipping

channel no mitigation measures can be taken against the loss of benthic fauna and

sediment along the route of the channel. All of the mobile non-sessile species have

the ability to vacate the area during dredging – benthic infaunal species do not have

this ability and will be lost from the dredging footprint during the course of the works.

It is expected that recolonisation of benthic infaunal communities in the newly

dredged channel will take between one and five years (a short term impact).

6.1.2. Deposition of sediments on mudflats and sandflats

The amount of sediment brought into suspension during dredging operations and

subsequently re-deposited in the harbour area is small. The vast majority of Sligo

Harbour will experience virtually imperceptible amounts (<2mm) of sedimentation

following completion of the dredging operations. A small number of localised sites,

such as Cartron Marsh, the area in the lee of the training wall and a few sheltered

pockets on the northern shore of the harbour will experience settling out of

suspended sediments in depths of more than 25mm. These sites cover, in

combination, an area of 3.5ha (0.07% of the overall SAC area, or 0.14% of the SAC

habitat “mudflats and sandflats not covered by seawater at low tide”).

No residual impact on the mudflats and sandflats in Sligo Harbour is expected due to

sediment deposition linked to the proposed dredging scheme. The predicted

sediment deposition levels are sufficiently low on the Cummeen Strand mudflats and

sandflats that mitigation measures are not necessary for the proposed dredging

scheme.

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6.2. Species in the Cummeen Strand/Drumcliff Bay SAC

6.2.1. Marine mammal species listed for the SAC – Annex II species (EU Habitats Directive)

Based on the results of the desk study and field studies undertaken in March 2011

(Section 4.4.4 of this Report) common seal are not regularly recorded in Cummeen

Strand/Sligo Harbour, Grey seal are even less frequently recorded. These animals

tend to occupy the more exposed bays to the north and south of Sligo Harbour. No

impact on these species is expected due to the proposed dredging scheme. No

mitigation measures are necessary for these species.

6.2.2. Fish species (Annex II)

Suspended sediment concentrations in the lower 0.5m of water column may

temporarily rise to significant levels for the period of spring tides during the 3 days of

water injection dredging before returning to background levels. During the

conventional dredging operations suspended sediment concentrations in the lower

0.5m of the water column are predicted to remain relatively low. River lamprey, Sea

lamprey and Atlantic salmon are most likely to move upstream via the navigation

channel where the peak suspended sediment concentrations during dredging in the

lowest 0.5m of the water column may be temporarily raised but mean concentrations

will remain within the Fish Directive recommended limit of 25 mg/l for salmonid

waters during the dredging period. Moreover, suspended sediment concentrations

are likely to be lower in the upper layers of the water column which salmon more

commonly utilise when swimming through estuarine and coastal waters.

Projected levels of suspended sediment are within recommended guidelines and are

not predicted to have any adverse effect the upstream and downstream migration of

River lamprey, Sea lamprey and Salmonid species.

6.2.3. Otter (Lutra lutra) (Annex II and IV)

Due to the adaptability and mobility of this species, it is unlikely that the intermittent

temporary dredging works will have a significant effect on these animals. No negative

impact is anticipated for this species. No mitigation measures are necessary for this

species.

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6.2.4. Marine mammals (Annex II and Annex IV)

No cetaceans are listed as qualifying species for the Cummeen Strand/Sligo Harbour

SAC, or as being of special importance to the SAC. The dolphins and harbour

porpoises recorded in the Cummeen Strand/Sligo Harbour SAC are highly mobile

species.

While harbour porpoises and dolphins do visit the Sligo Harbour on an infrequent

basis, they are not resident within this area. Dredging and disposal operations will not

deter them from entering the harbour and as they are mobile they can leave the site if

environmental conditions turn unfavourable, to return again once conditions become

favourable once again. Larger Odontocetes and Mysticetes have not been recorded

in this area. The proposed dredging works will have a negligible effect on cetaceans.

As a precautionary measure it is recommended that a Marine Mammal Observer

carries out several watches on the dredger during the dredging works.

6.2.5. Other fish species

Due to their mobility, impacts to fish species occurring subtidally in the Cummeen

Strand/Sligo Bay SAC are likely to be negative, slight and short-term. It is anticipated

that no mitigation measures will be necessary for these species.

In the case of European Eel (Anguilla anguilla) transiting through the site to and from

the Lough Gill SAC – these species may frequently encounter high suspended

sediment loads which do not appear to impact on migrations. Projected levels of

suspended sediment are within recommended guidelines and will not have an

adverse impact on upstream and downstream migrations.

6.3. Mitigation for Cummeen Strand SPA

6.3.1. Macrobenthos - food source for SPA bird species

The hydrodynamic modelling presented in Appendix F shows that the sediment put

into suspension by the dredger during water injection dredging will be dispersed

around the northern portion of Sligo Harbour. The sediment will be redistributed

during periods of higher current velocities during successive spring tides, before

eventually coming to rest in small deposits around the fringes of Sligo Harbour and

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Cartron Marsh (see Figure 8 in Appendix F). Some of the material will be

successfully transported out of the harbour and will settle out on the nearby sand

banks in depths of a few mm.

During subsequent conventional dredging, small amounts of sediment put in to

suspension by the dredger during dredging operations will be temporarily deposited

along the sides of the navigation channel and in sheltered areas along the north

shore of the harbour area. Significant deposition depths only occur in the sheltered

area along the coastline, particularly along the north shoreline (peak sedimentation

during dredging of 20-70mm). These peak values are typically of a short duration (a

matter of hours) and resuspension and transport of sediment during each tidal cycle

will reduce the scale of these deposits from the peak levels indicated in Figures 27

and 28 in Appendix F within hours and the residual amount and extent of deposited

sediment on final completion of operations will be substantially less (Figure 29). This

shows that the maximum final deposition depth following completion of operations

does not exceed 1mm in the majority of the harbour area and exceeds 25mm only in

very localised areas around the navigation channel and the northern shore of the

harbour. Overall, the amount of sediment deposited in the harbour area as a result

of the dredging will be insignificant and no residual impact is expected.

Due to the fact that the areas of Cummeen Strand SPA which are of greatest value to

birds will not be negatively impacted, it is suggested that no mitigation measures will

be necessary.

6.3.1.1. Noise impact on benthos

Impacts on benthos from noise in the vicinity of the dredging operation are expected

to be localised and temporary. The fact that the proposed dredging will take place in

an already busy port navigation channel suggests that the additional, temporary

noise loading of a dredger at work would be of minimal significance to benthos in the

vicinity of the dredged area. No mitigation measures will be necessary.

6.3.1.2. Mussel Beds

Impacts of the dredging plume on mussel beds in Sligo Harbour are considered

negligible. Mussels are very tolerant of extremely high turbidities (see Table 5-1).

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The proposed dredging scheme will not have any impact on mussels (adults, larvae

or spat). Neither suspended sediment levels nor sedimentation rates (as reported in

Appendix F, “Hydrodynamic Modelling”) reach lethal levels for mussels. No mitigation

measures will be necessary for this species.

6.3.1.3. Zostera Beds

Impacts of the dredging plume on the seagrass beds in Sligo Harbour are considered

to be negligible because the plumes of high turbidity and sedimentation do not reach

the seagrass beds documented in the area, and certainly not at levels that might

smother plants. Besides, intertidal seagrass is probably not affected much by

increased turbidity anyway, since it obtains most of its light during (day-time) periods

of low tide exposure (see Ochieng & Erftemeijer, 2009). Based on the final sediment

deposition depth computed for the Cummeen Strand seagrass habitat, on completion

of all dredging activities, it is anticipated that no mitigations measures will be

necessary.

6.3.2. Indirect Impacts on Natura sites in the wider locality, including Lough Gill SAC

It is likely that the three migratory species of this SAC, namely salmon and river and

sea lamprey, use the navigation channel during migrations between the sea and the

Lough Gill SAC. Timing of the works should take these migrations into account and,

despite the fact that the Lough Gill SAC will not be directly impacted by the proposed

dredging works, the link between freshwater and seawater habitats and species

should not be ignored. Consultation with Inland Fisheries Ireland should be

undertaken prior to the commencement of dredging works. No residual impacts are

anticipated.

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6.4. QUALIFYING SPECIES AND LISTED SPECIES OF IMPORTANCE FOR THE SPA

With successful implementation of mitigation measures during dredging, residual

impacts are expected to be neutral in the case of those species which occur in the

area of Sligo Harbour. No residual impacts on benthic fauna are expected.

7. Conclusions

The potential impacts during the carrying out and completion of the proposed

dredging scheme have been considered in the context of the Natura 2000 sites and

their conservation objectives. (The potential impacts and residual impacts are

summarised in Table 5-4).

7.1. Cummeen Strand/Drumcliff Bay SAC (Site code: 000627)

While there may be temporary impacts on certain species of interest for the cSAC

and other non-listed annexed species, these impacts will be highly localised and are

not expected to be of magnitude higher than moderate (Imperceptible or Slight if

using the EPA Guidelines).

As a result of the ecological impact assessment carried out it is considered that the

conservation objectives for this Special Area of Conservation will not be

compromised by the proposed development, nor will the proposed development have

any significant impact on the designated site or the habitats and species for which it

has been designated, either when taken alone or by any cumulative effects when

taken in combination with the other projects discussed in Section 5.2.4 above.

Should it be decided that, because of the effects on the site and its habitats or

species - such as they may be - it is necessary to carry out an appropriate

assessment under Article 6.3, this NIS provides the requisite information to ground

such an assessment. In the context of such an assessment it is the considered view

of the authors of this NIS that the proposed dredging project will have no adverse

effect on the integrity of the designated site as a whole or on any other designated

site.

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7.2. Cummeen Strand SPA (Site code: 004035)

Impacts are expected to be highly localised and mainly associated with the dredging

operations, and are not expected to affect the areas used by key SPA species.

Because of the manner in which the proposed channel dredging is to be carried out it

is anticipated that little effect of the dredging operation will reach the key areas of

Cummeen Strand. Impacts associated with the dredging operation itself will be

extremely localised and transient in nature owing to the relatively short periods of

operation in each location as the dredger moves along the channel path and as tides

dictate activity. This intermittent operation will enable benthic fauna to “recover”

quickly so that the food source for wading bird species will continue to be available.

Smothering by sedimentation will only be an issue for very small areas of substrate

along the navigation channel edges and along the northern shore of Sligo Harbour.

As a result of the ecological impact assessment carried out for the purpose of

preparing this NIS, it is considered that the “proposed” conservation objectives for the

proposed Special Protection Area will not be compromised by the proposed

development, nor by any cumulative effects, and no significant impact is anticipated

on any of the species for which the site was chosen for protection, either when taken

alone or by any cumulative effects when taken in combination with the other projects

discussed at paragraph 5.2.4 above.

In the context of an Appropriate Assessment under Article 6.3 it is the considered

view of the authors of this NIS that the proposed development will have no adverse

impact on the integrity of the designated site as a whole or on any other nearby

designated site.

7.3. Lough Gill SAC (Site code: 001976)

No direct impacts are anticipated for the Lough Gill SAC as it is a

terrestrial/freshwater site located upstream of Sligo town. No residual impact is

anticipated on migratory species inhabiting the site if mitigation measures are

adopted and any conditions arising strictly adhered to.

8. Acknowledgements

The following are thanked for providing assistance in compiling this report:

Gerard Morgan, Aquatic Services Unit, UCC

Michelle Cronin, UCC

Valerie Cummins, Coastal & Marine Resources Centre, UCC

Irish Whale and Dolphin Group

Michael Crowley, Riverbank Mussels Ltd., Co. Wexford

John Lambe, Wexford County Council

Dr Susan Coughlan, Sea Fisheries Protection Authority

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Peralta, G., Perez-Lorens, J.L., Hernandez, I. & J.J. Vergara. 2002. Effects of light availability on growth, architecture and nutrient content of the seagrass Zostera noltii Hornem. Journal of Experimental Marine Biology and Ecology 269: 9–26.

Picton, B.E. and Costello M. J. (editors). 1998. BioMar biotope viewer: a guide to marine habitats, fauna and flora of Britain and Ireland. Environmental Sciences Unit, Trinity College, Dublin. ISBN 0 9526 735 4 1

Pielou, E.C. (1977). Mathematical ecology. Wiley-Water science Publication, John

Wiley and Sons. pp.385.

Pollock, C. M., J.B. Reid, A. Webb and M.L Tasker, 1997. The Distribution of Seabirds and Cetaceans in the Waters Around Ireland. JNCC Report, No. 267

Prins, T.C. and A.C. Smaal (1989) Carbon and nitrogen budgets of the mussel Mytilus edulis L, and the cockle Cerastoderma edule (L.) in relation to food quality Scientia Mar 53: 477-482

Pugh, D.T., 1982. A comparison of recent and historical tides and mean sea-levels off Ireland. Geophysical Journal of the Royal Astronomical Society Vol. 71, Issue 3, pages 809–815, December 1982

Ryle, T., A. Murray, K. Connolly & M. Swann, 2009. COASTAL MONITORING PROJECT 2004-2006. A report to the National Parks and Wildlife Service, Dublin.

Shepherd, S.A., McComb, A.J., Bulthuis, D.A., Neverauskas, V., Steffensen, D.A. & R. West. 1989. Decline of seagrasses. In: Larkum, A.W.D., McComb, A.J., Shepherd, S.A. (Eds.), Seagrasses: A Treatise on the Biology of Seagrasses with Special Reference to the Australian Region. Elsevier, North Holland, pp. 346–387.

S.I. No. 291/1985. Statutory Instrument – European Communities Conservation of Wild Birds) Regulations 1985.

References

Summers, C.F., Warner, P.J., Nairn, R.G.W., Curry, M.G. & Flynn, J. (1980). An assessment of the status of the common seal Phoca vitulina vitulina in Ireland. Biol. Conserv. 17: 115-123.

Treweek, J. 1999. Ecological Impact Assessment. Blackwell Science Limited: Oxford. 351 pp.

Vermaat, J.E., N.S.R. Agawin, M.D. Fortes & J.S. Uri. 1997. The capacity of seagrasses to survive increased turbidity and siltation: the significance of growth form and light use. Ambio 26(8): 499-504.

Wentworth, C. K., 1922. A scale of grade and class terms for clastic sediments; Journal of Geology, 30: 377-392.

Whilde, A., 1993. Irish Red Data Book 2: Vertebrates – Threatened Mammals, Birds, Amphibians and Fish in Ireland. Dr. J. K. Partridge (ed.). Published by HMSO, Belfast on behalf of Environment Service (Dept. of the Env. Northern Ireland) and The OPW, (Rep. of Ireland) 224 pages

Widdows, J., P. Fieth & C.M. Worral. 1979. Relationship between seston, available food and feeding activity in the common mussel Mytilus edulis. Mar. Biol. 50: 195-207.

Wildlife Service, 1989. Index to Areas of Scientific Interest. WS. Dublin.

Wingfield Gibbons, D., J.B. Reid, R.A. Chapman, 1993. The New Atlas of Breeding Birds in Britain and Ireland: 1988-1991. British Trust for Ornithology. Published by T. & A. D. Poyser, 24-28 Oval Road, London NW1 7DX. ISBN 0-85661-075-5

www.iwdg.ie, 2010. Web resource at Irish Whale and Dolphin Group accessed in November 2010.

Young, R. (Ed.) 1977. Planning for the Use of Irish Sand Dune Systems. Proceedings of a Conference held in Wexford, April 1977. An Foras Forbatha.

9.1. Additional information sources including web resources

Legislation:Wildlife Act, 1976. Reports/ Literature etc:An Foras Forbatha County Reports Leaflets (general):Irish Geological Association Field Guide Series: Regional and local tourism authority leaflets and guides Local authority leaflets. NPWS, 2010: Internal Databases, Reports etc. National ASI Survey Guidelines for Ecologists Version 1.0; March 1993 NPWS Internal reports not listed above in the bibliography. Rare Plant Survey R.FitzGerald. 1992-1993 Protected Plant Data Base Threatened Plant Data Base Atlas 2000- Scarce Plant Project . J. Neff 1996 - 1998 Scarce Plant Database Plant Protection Order 1987. NHA Data Base

References

Inventory of Areas of Scientific Interest WS Salt marsh Inventory. 1997 - List of Provisional Special Areas of Conservation IWRB Wetland Data Sheets Greenland White-fronted Goose Inventory 1982-83. Breeding Census of Grey Seals 1984. Proposals for Nature Reserve designation. Statutory Instruments relating to Nature Reserves, Refuges etc. Leaflets:A Guide to Lough Hyne - leaflet. http://www.coastalhelicopterview.ie

References

NIS Appendix A A1

APPENDIX A - BIOMAR SURVEY DATA

From – BioMar survey, Co. Sligo, 1996

Biomar sites (from north to south – for locations refer to Figure 6 in the main report body).

Site 1 Blue Lough Bay, Ballyconnell Point, S Donegal Bay

Latitude 54° 21.90' N Longitude 008° 39.89' E

Min depth 0.3m Max depth 3.5m

Grid reference G567464

Site description The site is a large, boulder-filled, bedrock rimmed shore set in a small

bay. This bay is part of the south shore of a large, west-facing bay. At

the edges of the small bay bedrock extended partly out as breakwaters.

The inner part of the bay consists of boulders and large areas of

standing water. The largest of these pools had extensive growths of

Zostera angustifolia and a rich flora of red and brown algae.

Habitats present Upper shore pools with Paracentrotus lividus.

Bedrock with Fucus vesiculosus.

Boulders on bedrock and shingle with Fucus serratus.

Boulders on low shore with Laminaria digitata.

A large midshore pool with Zostera angustifolia.

Biotopes Coralline crusts and Paracentrotus lividus in shallow eulittoral rockpools

Fucus vesiculosus and barnacle mosaics on moderately exposed mid

eulittoral rock

Osmundea (Laurencia) pinnatifida and Gelidium pusillum on moderately

exposed mid eulittoral rock

Fucoids and kelps in deep eulittoral rockpools

Laminaria digitata and under-boulder fauna on sublittoral fringe boulders

Fucoids and kelps in deep eulittoral rockpools

Seaweeds in sediment (sand or gravel)-floored eulittoral rockpools

Substrate Bedrock, boulders, cobble/pebble, gravel

NIS Appendix A A2

Site 2 Ballyconnell Point, S Donegal Bay (subtidal)


Min depth -13.6m Max depth -28.6m

Grid reference G560461

Site description The site was adjacent to a very exposed headland near the entrance of a

west facing large bay. There was a large cliff with abundant Corynactis

viridis from 13 m BCD to approximately 26 m BCD. At the bottom of the

cliff there was stepped limestone bedrock with Caryophyllia smithii and

Corynactis viridis.

Habitats present Vertical limestone cliff, very exposed

Horizontal circalittoral limestone, very exposed.

Biotopes Corynactis viridis, Metridium senile and Alcyonium digitatum on exposed

or moderately exposed vertical infralittoral rock

Phakellia ventilabrum and axinellid sponges on deep exposed

circalittoral rock

Substrate Bedrock

Site 3 Ardtermon Strand, Sligo Bay


Min depth 0m Max depth 0m

Grid reference G581427 Sheltered

Site description The site is situated on the northern shore of Drumcliff Bay, in Sligo Bay

on the west coast of Ireland. The beach lies on the eastern side of a

small peninsula - Raghly. It is a sandy beach, approx. 2 km long and 500

m wide. A short storm beach leads to a short steep sandy stretch with

patches of fucoids then to a very wide muddy sand flat with ripple marks

and standing water on the surface. The beach faces south-east and is

protected from prevailing winds by the peninsula. There is evidence of a

diverse fauna, including Arenicola casts, Lanice tubes, live Cardium on

the surface, paired shells of various bivalve species, including Ensis,

Venus striatula, Diplodonta? Much Zostera debris. Some black patches

on sand surface. There were small Zostera beds and large areas of

Laminaria around low water. The transect was oriented 300 degrees.

Habitats present Talitrid zone, muddy sand beach

Midshore, muddy sand beach

Lower shore, muddy sand beach

Biotopes Burrowing amphipods and polychaetes in clean sand shores

Substrate Sand

NIS Appendix A A3

Site 4 Ballygilgan Strand, Drumcliff Bay, Sligo Bay



Grid reference G645432 Sheltered

Site description The site is situated on the north side and inner part of a large, sheltered

west facing bay (Drumcliff Bay) on the north-west coast of Ireland. A

large dune and grassland peninsula extending northward into the bay

from the southern shore shelters the site on the seaward (west) side. A

transect was taken from the end of a boreen, at the eastern end of

Ballygilgan strand, at a magnetic bearing of 250 degrees, parallel to the

Carney river estuary, to the main channel. The shore width was

approximately 500 m at this point. Drumcliff Bay is known to be an

important feeding area for birds and contains several Ramsar sites for

geese. This site at Ballygilgan Strand is included in a proposed NHA.

The upper part of the site was extremely sheltered and was fringed by

grassland with some stones and boulders at the top of the shore. Fucus

vesiculosus, Pelvetia canaliculata and Ascophyllum nodosum were

occasional on the boulders. Arenicola marina casts were common to

abundant on the upper shore where the sediment was dry firm, muddy

sand. In the midshore the sediment was sandier with small pools of

standing water and occasional clumps of algae. Cerastoderma edule and

Arenicola marina were common with occasional small banks of Mytilus

edulis. The lower shore had a firmer sand and shell substrate except at

the channel edge which was muddier. A large shellfish farm (clams and

Pacific oysters) dominated the lower shore area to the west of the

transect. On the opposite side of the main channel approximately 40

seals were resting on the shore of a sand bank.

Habitats present Upper shore

Midshore

Lower shore

Lower midshore

Biotopes

Substrate Sand/mud

NIS Appendix A A4

Site 5 Inner Drumcliff Bay, Sligo Bay



Grid reference G665421 Very sheltered

Site description The site is situated in the inner part of a large sheltered west facing bay

(Drumcliff Bay) on the north-west coast of Ireland. The mudflats in the

bay are thought to be important feeding grounds for birds. A transect

was taken on the south side of the inner bay, (from the end of a boreen

at G 669 408) at a magnetic bearing of 318 degrees to the channel of the

Drumcliff river across a very gently sloping mudflat which is typical of the

area. The shore width was approximately 1.8 km at this point. A band of

Zostera, approximately 100 m in width extended along the upper shore.

Arenicola marina were common to abundant on the upper and midshore.

Cerastoderma edule, Macoma balthica, Tellina tenuis and Nephtys sp.

were also frequent to common on the midshore.

Habitats present Top of shore, talitrid sample

Upper shore.

Upper midshore

Midshore

Lower shore

Biotopes

Substrate Cobble,pebble, sand, mud

Site 6 Rosses Point, Sligo Bay



Grid reference G628405 Exposed

Site description The site is located on the west coast of Ireland, in Sligo Bay. It lies at the

western end of a small peninsula which separates Sligo Harbour from

Drumcliff Bay. It is a sandy beach, approx. 1.5 km long and 200 m wide,

composed of fine, well sorted sand, backed by low dunes. Access is via

a path from the car park. The slope is gentle, with a single runnel and

bar. There is little surface evidence of life. No lugworm casts. Sparse

Lanice tubes on lower shore. No paired bivalve shells. It is a blue flag

beach. Sampling showed the presence of polychaetes, Angulus tenuis

was fairly common and juvenile Donax were present on the lower shore.

The transect lay west of Bomore Point at 280 degrees. Crangon were

present in midshore runnel and at low water and also Eurydice were

common at the water's edge.

NIS Appendix A A5

Habitats present Sandy beach, upper shore, talitrid zone

Sandy beach, midshore

Sandy beach, lower shore


Substrate Sand

Site 7 Dorrins Strand, Sligo Harbour, Sligo Bay




Site description The site is located towards the outer part, and on the southern shore of a

large narrow bay (Sligo Harbour) on the north-west coast of Ireland. The

mouth of the bay is sheltered from the prevailing westerly winds by two

islands (Coney Island and Oyster Island) with the main drainage channel

running on the north side of the bay. A transect was taken from the

southern end of the "roadway" to Coney Island, at a magnetic bearing of

334 degrees, across a large sand flat to the edge of the main channel, to

the south of Oyster Island, a distance of approximately 2 km. The shore

was backed by grassland and a narrow strip of salt marsh giving way to

fine rippled sand with a thin layer of standing water. A wide (100 m)

shallow channel (2-5 cm), split by a sandbar, was located approximately

100 m from the shore. The bed of the channel was soft rippled sand with

frequent cockles, Arenicola marina castings 1-9 per metre squared and

frequent clumps of Enteromorpha sp. on the surface. To the north of this

channel the sand was firm and, for the most part, covered with a layer of

standing water and had an anaerobic layer 1-2 cm below the surface. A.

marina castings were visible on the surface at densities of 1-9 per metre

squared with Cerastoderma edule present in the top 10-15 cm of

sediment at densities of 1-5 per metre squared. Fine tube worms were

also common. The density of cockles increased 1.5 km out from the

shore with 18 per 0.25 metres squared recorded. At 1.75 km out from the

shore the surface rose gently to the top of a large, sandbank running

adjacent to the main channel. The sediment on the bank was coarse and

dry with Scolelepis worms abundant and Lanice conchilega castings rare

to occasional (1 per 5 metres squared). The anoxic layer was greater

than 25 cm below the surface. At 2 km out from the shore, the sandbank

sloped down to the main channel with a dense band of Lanice

conchilega and filamentous brown algae 50 m from the channel. Ulva sp.

was also present attached to worm tubes. The anoxic layer was 10 cm

below the surface in the coarse sand and broken shell at the channel

NIS Appendix A A6

edge.


Midshore

Lower shore

Biotopes

Substrate Sand

Site 8 Cummeen Strand, Sligo Harbour, Sligo Bay




Site description The site is located towards the inner part of a large, sheltered bay (Sligo

Harbour) with two narrow north-west facing entrances. The bay is in the

north-west of Ireland. A transect was taken from the sea wall west of

Gibralta Point, on the southern shore, at a magnetic bearing of 342

degrees across a sand flat, to the main channel on the north side of the

bay. The transect was approximately 2 km long and crossed a small

shallow channel about 50 m from the sea wall. The beach started with an

area of mud, gravel and stone sloping gently to the shallow channel and

was characterised by Enteromorpha spp., Ulva sp , Fucus vesiculosus,

F. ceranoides and Scrobicularia plana. Beyond the channel the beach

had a short steep upward slope characterised by small burrows with very

small gastropods 1-2 mm in the burrows. The beach appeared flat for

600 m and was characterised by Arenicola marina for the first 300 m and

then by a mixture of A. marina and Cerastoderma edule. Between 600

and 700 m there was a dense mussel bed with mussel and dead cockle

shells banded together on the shoreward side. Some F. vesiculosus and

Enteromorpha spp. were present on the bed. Seaward of this the shore

sloped very gently to the channel and was covered with standing water

1-5 cm deep with cockles, in particular small cockles, present for the

next 200 m. After this cockles were occasional as were A. marina casts.

The sand was very flat with small tubes present. Close to the channel

the sand became rippled and algae, in particular Polysiphonia sp. or

Ceramium sp. were attached to dead cockle shells. Lanice conchilega

were frequent at the channel edge. Across most of the beach

Enteromorpha spp. were present attached to dead shells. The anoxic

layer varied from 1 to 10 cm below the surface but was generally 1 to 5

cm beneath the surface. Clam beds were present on the beach.

NIS Appendix A A7


Mid shore

Lower shore

Biotopes

Substrate Gravel, sand, mud, other

Site 9 Culleenamore Strand, Ballysodare Bay




Site description The site surveyed lies inside the north-west edge of Ballysodare Bay, in

Sligo Bay, on the west coast of Ireland. It is an extensive sand flat,

approx. 1.2 km long by approx. 800 m wide. It faces south into

Ballysodare Bay so there is a very limited fetch. It is a fine sandy beach

with a short steep upper section, leading to an almost flat middle section

followed by a steeper drop to the channel. Standing water on surface at

low tide. It is backed by sand dunes. Live cockles, including juveniles are

common on sand surface. Arenicola casts are common. Dense patches

of Lanice on lower shore. Sampling showed the fauna to be quite rich,

mainly of polychaetes, with cockles and Angulus. Transect taken just

north of car park at 200 degrees.

Habitats present Talitrid zone, upper shore, sand flat

Midshore, sand flat

Lower shore, sand flat


Substrate Sand

Site 10 Cartonabree, Ballysodare Bay, Sligo Bay




Site description The site is located on the northern side of the inner and sheltered part of

a north-west facing bay on the north-west coast of Ireland. The shore

was backed by grassland and a band of small, algae covered rocks and

boulders lined the top of the shore. A transect was taken from the centre

of a small shallow bay at G 634 314 at a magnetic bearing of 174

degrees to the channel of the Ballysodare river on the south side of

Ballysodare Bay. The shore was approximately 1.15 km at this point and

punctuated by a number of shallow side channels between slightly raised

NIS Appendix A A8

sandflats. The sediment was generally firm sand though slightly muddier

on the upper shore, while plant detritus and some mud was found

adjacent to the main river channel. The depth to the anoxic layer was

typically 2 to 3 cm. The upper shore had bands of Pelvetia canaliculata,

Ascophyllum nodosum (with the epiphyte Polysiphonia lanosa) and

Fucus vesiculosus (5 to 19% cover). Below the algae bands Arenicola

marina were abundant for 200 m reducing to common for the remainder

of the shore. Cerastoderma edule and Mya arenaria were frequent to

common on the midshore with fine worm castings frequent to common

on the lower shore.


Upper midshore

Midshore

Lower shore

Biotopes

Substrate Sand, gravel, mud

NIS Appendix B

APPENDIX B – NATURA 2000 SITE SYNOPSES, STANDARD DATA FORMS AND CONSERVATION OBJECTIVES

NIS Appendix B

Generic Conservation Objective16 April 2012

Conservation Objectives for Cummeen Strand SPA [004035]

European and national legislation places a collective obligation on Ireland and its citizens tomaintain habitats and species in the Natura 2000 network at favourable conservation condition.The Government and its agencies are responsible for the implementation and enforcement ofregulations that will ensure the ecological integrity of these sites.

Favourable conservation status of a habitat is achieved when:• its natural range, and area it covers within that range, are stable or increasing, and• the specific structure and functions which are necessary for its long term maintenance existand are likely to continue to exist for the foreseeable future, and• the conservation status of its typical species is favourable.

The favourable conservation status of a species is achieved when:• population dynamics data on the species concerned indicate that it is maintaining itself on along term basis as a viable component of its natural habitats, and• the natural range of the species is neither being reduced nor is likely to be reduced for theforeseeable future, and• there is, and will probably continue to be, a sufficiently large habitat to maintain itspopulations on a long term basis.

Objective: To maintain or restore the favourable conservation condition of the bird specieslisted as Special Conservation Interests for this SPA:

The overall aim of the Habitats Directive is to maintain or restore the favourable conservationstatus of habitats and species of community interest. These habitats and species are listed inthe Habitats and Birds Directives and Special Areas of Conservation and Special ProtectionAreas are designated to afford protection to the most vulnerable of them. These twodesignations are collectively known as the Natura 2000 network.

The maintenance of habitats and species within Natura 2000 sites at favourable conservationcondition will contribute to the overall maintenance of favourable conservation status of thosehabitats and species at a national level.

Start 004035

Branta bernicla hrota [wintering]Haematopus ostralegus [wintering]Tringa totanus [wintering]Wetlands []

For more information please go to: www.npws.ie/protectedsites/conservationmanagementplanning

NPWS (2011) Conservation objectives for Cummeen Strand SPA [004035]. Generic Version 4.0. Department ofArts, Heritage & the Gaeltacht.

Citation:

Appendix B B1

SITE SYNOPSIS

SITE NAME: CUMMEEN STRAND SPA

SITE CODE: 004035

Cummeen Strand is a large shallow bay stretching from Sligo town westwards to Coney Island. It is one of three estuarine bays within Sligo Bay, with Drumcliff Bay to the north and Ballysadare Bay to the south. The Garavogue River flows into the bay and forms a permanent channel.

At low tide, extensive sand and mud flats are exposed. These support a diverse macro-invertebrate fauna which provide the main food supply for the wintering waterfowl. Invertebrate species such as lugworm (Arenicola marina), ragworm (Hediste diversicolor), cockles (Cerastoderma edule), sand mason (Lanice conchilega), Baltic tellin (Macoma balthica), spire shell (Hydrobia ulvae) and mussels (Mytilus edulis) are frequent. Of particular note is the presence of eelgrass (Zostera noltii and Z. angustifolia) beds, which provide a valuable food stock for herbivorous wildfowl. The estuarine and intertidal flat habitats are of conservation significance and are listed on Annex I of the EU Habitats Directive. Areas of salt marsh fringe the bay in places and provide roosting sites for birds during the high tide periods. There are sand dunes at Killaspug Point and Coney Island, with a shingle spit at Standalone Point near Sligo town.

Cummeen Strand is of ornithological importance as it supports important concentrations of wintering waterfowl. The site supports an Internationally Important flock of Brent Geese (peak of 232 individuals in the winter of 1999/00, with the mean of peak monthly counts in the period 1996/99 (except 1998) being 228, peaking at 309) and Nationally Important populations of a further two species – Oystercatcher 891 and Redshank 501 (all figures are average peaks for the period). Other species which occurred in significant numbers included Shelduck 80, Wigeon 178, Teal 70, Mallard 170, Red-breasted Merganser 17, Golden Plover 567, Lapwing 734, Knot 18, Sanderling 18, Dunlin 601, Bar-tailed Godwit 57, Curlew 546, Greenshank 18 and Turnstone 80. Whooper Swans also occurred (9), though they are not regular visitors. The presence of Golden Plover, Bar-tailed Godwit and Whooper Swan is of particular note as these species are listed on Annex I of the EU Birds Directive.

This site is of high ornithological importance, with one species having a population of International Importance and two having populations of National Importance. In addition, there are three species that are listed on Annex I of the Birds Directive.The site is also important as a component of the much larger Sligo Bay complex.

28.02.2002

Appendix B B2

Site code: IE0004035 NATURA 2000 Data Form

NATURA 2000Site code:

STANDARD DATA FORM

FOR SPECIAL PROTECTION AREAS (SPA)

FOR SITES ELIGIBLE FOR IDENTIFICATION AS SITES OF COMMUNITY IMPORTANCE (SCI)

AND

FOR SPECIAL AREAS OF CONSERVATION (SAC)

Start Form

NF004035

1

Appendix B B3


1. SITE IDENTIFICATION

1.5. RELATION WITH OTHER NATURA 2000 SITES:

1.1. TYPE 1.2. SITE CODE 1.3. COMPILATION DATE 1.4. UPDATE

J IE0004035 200311

NATURA 2000 SITE CODES

IE0000627

1.6. RESPONDENT(S):National Parks & Wildlife Service of the Department of the Environment, Heritage and Local Government. 7 Ely Place, Dublin 2, Ireland.

DATE SITE PROPOSED AS ELIGIBLE AS SCI: DATE CONFIRMED AS SCI:

DATE SITE CLASSIFIED AS SPA:

199502

DATE SITE DESIGNATED AS SAC:

1.7. SITE NAME:Cummeen Strand SPA

1.8. SITE INDICATION AND DESIGNATION/CLASSIFICATION DATES:

2

Appendix B B4


2.1. SITE CENTRE LOCATION

LONGITUDE LATITUDE

W

W/E (Greenwich)

8 32 0 54 17 30

2.2. AREA (HA): 2.3. SITE LENGTH (KM):

1732.43

2.4. ALTITUDE (M):

-5

MINIMUM MAXIMUM MEAN

5 -2

2. SITE LOCATION

2.6. BIOGEOGRAPHIC REGION:

Alpine Atlantic Continental MacaronesianBoreal Mediterranean

NUTS CODE REGION NAME % COVER

2.5. ADMINISTRATIVE REGION:

IE011 Border 1

9Marine area not covered by a NUTS-region

3

Appendix B B5


3. ECOLOGICAL INFORMATION

3.1. HABITAT types present on the site and assessment for them:

ANNEX I HABITAT TYPES:

CODE %COVER REPRESENTATIVITY RELATIVE SURFACE CONSERVATION STATUS

GLOBAL ASSESSMENT

4

Appendix B B6


3.2. SPECIES

covered by Article 4 of Directive 79/409/EEC

and

and

listed in Annex II of Directive 92/43/EEC

site assessment for them

5

Appendix B B7


3.2.a. BIRDS listed on Annex I of Council directive 79/409/EEC

3.2.b. Regularly occuring Migratory Birds not listed on Annex I of Council directive 79/409/EEC

3.2.c. MAMMALS listed on Annex II of Council directive 92/43/EEC

PopulationSITE ASSESSMENT

MigratoryResidentPOPULATIONNAMECODE

Conservation Isolation

Breed Winter Stage

567 iPluvialisapricaria

A140 C B C

57 iLimosa lapponicaA157 C B C




Breed Winter Stage

232 iBranta berniclaA046 C A C80 iTadorna tadornaA048 C A C178 iAnas penelopeA050 C B C70 iAnas creccaA052 C B C170 iAnas platyrhynchosA053 C B C17 iMergus serratorA069 C B C

891 i Haematopusostralegus

A130 C A C

32 iCharadriushiaticula

A137 C B C

734 iVanellus vanellusA142 C B C104 iCalidris canutusA143 C B C18 iCalidris albaA144 C B C601 iCalidris alpinaA149 C B C546 iNumenius arquataA160 C A C501 iTringa totanusA162 C A C18 iTringa nebulariaA164 C A C80 iArenaria interpresA169 C B C353 iLarus ridibundusA179 C B C43 iLarus canusA182 C B C

6

Appendix B B8


3.2.d. AMPHIBIANS and REPTILES listed on Annex II of Council directive 92/43/EEC

3.2.e. FISHES listed on Annex II of Council directive 92/43/EEC

3.2.f. INVERTEBRATES listed on Annex II of Council directive 92/43/EEC

3.2.g. PLANTS listed on Annex II of Council directive 92/43/EEC

7

Appendix B B9


3.3. Other Important Species of Flora and Fauna

(B = Birds, M = Mammals, A = Amphibians, R = Reptiles, F = Fish, I = Invertebrates, P = Plants)

SCIENTIFIC NAME POPULATION MOTIVATIONB M A R F I P

GROUP

B Ardea cinerea 13 i D

8

Appendix B B10


4. SITE DESCRIPTION

4.1. GENERAL SITE CHARACTER:

Habitat classes % cover

Tidal rivers, Estuaries, Mud flats, Sand flats, Lagoons (including saltwork basins)

95

Salt marshes, Salt pastures, Salt steppes 2Shingle, Sea cliffs, Islets 2

Other land (including Towns, Villages, Roads, Waste places, Mines, Industrial sites)

1

Total habitat cover 100 %

Other site characteristicsCummeen Strand SPA comprises the greater part of Sligo Harbour, the middle one of the three 'arms' forming Sligo Bay. The site extends for up to 7 km from east to west and has an average width of c.2.5 km. The site is the estuary of the Garavoge River, a short slow-flowing river which flows from Lough Gill. The harbour is very enclosed, with the mouth of the harbour being sheltered by two islands (Coney Island and Oyster Island). A large proportion of the estuary is intertidal (> 80%). Sediments are predominantly sands or coarser materials, though muddy sands or muds also occur. Zostera beds are present. The intertidal sand and mud flats are fringed by salt marshes in places but mostly stony shoreline. Sligo Harbour is a regional port for the town of Sligo.

4.2. QUALITY AND IMPORTANCE:Cummeen Strand is of importance for the diversity of wintering waterfowl and is an integral part of the larger unit of Sligo Bay. The site has an internationally important population of Branta bernicla hrota and supports nationally important numbers of Haematopus ostralegus and Tringa totanus. Both Pluvialis apricaria and Limosa lapponica utilise the site though in relatively low numbers. The intertidal flats, which have well-developed macro-invertebrate communities and Zostera beds, provide good feeding grounds for the wintering birds. Birds roost on the salt marshes and upper shoreline though on high tides some may leave the site to roost elsewhere.

4.3. VULNERABILITYThere are no significant imminent threats to the wintering bird populations.Shellfish farming occurs in Sligo Harbour on a large scale and could cause localised disturbance to sediments and to the wintering birds. Sewage, largely untreated, currently enters the site from Sligo town, though this may not necessarily have adverse effects on the birds. A new treatment works is to be built which will significantly improve water quality.

4.4. SITE DESIGNATION:

4.5. OWNERSHIPState : Department of Communications, Marine and Natural Resources

Private

9

Appendix B B11


4.6. DOCUMENTATIONColhoun, K. (2001). I-WeBS Report 1998-99. BirdWatch Ireland, Dublin.

Curtis, T.G.F. and Sheehy Skeffington, M.J. (1998). The salt marshes of Ireland: an inventory and account of their geographical variation. Biology andEnvironment, Proceedings of the Royal Irish Academy 98B: 87-104.

Falvey, J.P., Costello, M.J. and Dempsey, S. (1997). Survey of intertidal biotopes in estuaries in Ireland. Unpublished report to the National Parks and Wildlife Service, Dublin.

Goodwillie, R. (1972). A Preliminary Report on Areas of Scientific Interest in County Sligo. An Foras Forbartha, Dublin.

Hunt, J., Derwin, J., Coveney, J. and Newton, S. (2000). Republic of Ireland.Pp. 365-416 in Heath, M.F. and Evans, M.I. (eds). Important Bird Areas in Europe: Priority Sites for Conservation 1: Northern Europe. Cambridge, UK: BirdLife International (BirdLife Conservation Series No. 8).

Irish Wetland Birds Survey (I-WeBS) Database, 1994/95-2000/01. BirdWatch Ireland, Dublin.

Jennings O'Donovan and Partners (1998). Sligo Main Drainage Waste Water Treatment Works. Environmental Impact Statement, Main Report Volumes 1 and 2.Report prepared for Sligo Corporation.

McGarrigle M.L., Bowman J.J., Clabby K.J., Lucey J., Cunningham P., MacCarthaigh M., Keegan M., Cantrell B., Lehane M., Clenaghan C. and Toner P.F. (2002). Water Quality in Ireland 1998-2000. Environmental Protection Agency, Wexford.

Merne, O.J. (1989). Important bird areas in the Republic of Ireland. In: Grimmett, R.F.A. and Jones, T.A. (eds). Important Bird Areas in Europe. ICBP Technical Publication No. 9. Cambridge.

Sheppard, R. (1993). Ireland's Wetland Wealth. IWC, Dublin.

10

Appendix B B12


5. SITE PROTECTION STATUS AND RELATION WITH CORINE BIOTOPES

5.1. DESIGNATION TYPES at National and Regional level:

5.2. RELATION OF THE DESCRIBED SITE WITH OTHER SITES:

5.3. RELATION OF THE DESCRIBED SITE WITH CORINE BIOTOPE SITES:

designated at National or Regional level:

designated at International level:

CORINE SITE CODE OVERLAP TYPE % COVER

800000473

11

Appendix B B13


6. IMPACTS AND ACTIVITIES IN AND AROUND THE SITE

6.1. GENERAL IMPACTS AND ACTIVITIES AND PROPORTION OF THE SURFACE OF THE SITE AFFECTED

6.2. SITE MANAGEMENT AND PLANS

IMPACTS AND ACTIVITIES WITHIN the site

IMPACTS AND ACTIVITIES AROUND the site

CODE INTENSITY % OF SITE INFLUENCE200 10A B C + 0 -220 20A B C + 0 -410 1A B C + 0 -520 10A B C + 0 -700 100A B C + 0 -802 1A B C + 0 -

CODE INTENSITY INFLUENCE120 A B C + 0 -400 A B C + 0 -410 A B C + 0 -502 A B C + 0 -

BODY RESPONSIBLE FOR THE SITE MANAGEMENT

SITE MANAGEMENT AND PLANS

A Conservation Plan for the management of this site is being prepared.

12

Appendix B B14


7. MAPS OF THE SITE

- Physical map

- Aerial photograph(s) included:

8. SLIDES

13

Appendix B B15

Appendix B B16

Generic Conservation Objective18 July 2011

Conservation Objectives for Cummeen Strand/Drumcliff Bay (Sligo Bay)SAC [000627]

European and national legislation places a collective obligation on Ireland and its citizens tomaintain habitats and species in the Natura 2000 network at favourable conservationcondition. The Government and its agencies are responsible for the implementation andenforcement of regulations that will ensure the ecological integrity of these sites.



Objective: To maintain or restore the favourable conservation condition of the Annex Ihabitat(s) and/or the Annex II species for which the SAC has been selected:



Start 000627

Vertigo angustior[1014]Petromyzon marinus[1095]Lampetra fluviatilis[1099]Estuaries[1130]Mudflats and sandflats not covered by seawater at low tide[1140]Phoca vitulina[1365]Embryonic shifting dunes[2110]Shifting dunes along the shoreline with Ammophila arenaria ("white dunes")[2120]* Fixed coastal dunes with herbaceous vegetation ("grey dunes")[2130]Juniperus communis formations on heaths or calcareous grasslands[5130]* Petrifying springs with tufa formation (Cratoneurion)[7220]


NPWS (2011) Conservation objectives for Cummeen Strand/Drumcliff Bay (Sligo Bay) SAC [000627]. GenericVersion 3.0. Department of Arts, Heritage & the Gaeltacht.

Citation:

Appendix B B17

SITE SYNOPSIS

SITE NAME: CUMMEEN STRAND/DRUMCLIFF BAY (SLIGO BAY)

SITE CODE: 000627

This large coastal site extends from Cullamore in the north-west to Killaspug in the south-west, and from Sligo town in the south-east to Drumcliff village in the north-east. It encompasses two large, shallow bays (Drumcliff Bay and Sligo Harbour), Ardboline and Horse Islands, sand dunes and sand hills at Rosses Point, Killaspug, Yellow Strand and Coney Island, grassland at Ballintemple and Ballygilgan (Lissadell) and a variety of other habitats (woodland, salt marsh, sandy beaches, boulder beaches, shingle, fen, freshwater marshes, rocky sea cliffs, lakes). The site is largely underlain by Carboniferous limestone, but acidic rocks are also found on the Rosses Point peninsula. At Serpent Rock in the north-western section of the site the most complete section of the north-western Carboniferous strata is exposed. Here are found an excellent series of fossilised corals which, in some strata, stand out from the rock matrix.

The dominant habitats on the site are estuaries and intertidal sand and mud flats. Sligo Harbour receives the waters of the Garavogue River, which flows from Lough Gill, while Drumcliff Bay receives the Drumcliff River which flows from Glencar Lough. At low tide extensive areas of intertidal flats are exposed in both of these sheltered estuarine bays. The intertidal flats support a diverse macrofauna, with invertebrate species such as lugworm (Arenicola marina), cockles (Cerastodermaedule), sand mason (Lanice conchilega), Baltic tellin (Macoma balthica), spire shell (Hydrobia ulvae) and mussels (Mytilus edulis) being frequent. Of particular note is the presence of eelgrass (Zostera noltii and Z. angustifolia) beds in both bays. Both estuaries and intertidal flats are of conservation significance and are listed on Annex I of the EU Habitats Directive. Areas of salt marsh fringe both bays in places.

Sand dunes, sand hills and dune grassland are found at Rosses Point, Killaspug, Yellow Strand and Coney Island. The dominant species of the dune grassland behind Yellow Strand are Sand Sedge (Carex arenaria) and Meadow-grass (Poa pratensis),with associated species including Lady's Bedstraw (Galium verum), Mouse-ear Hawkweed (Hieracium pilosella), Common Milkwort (Polygala vulgaris), Common Dog-violet (Viola riviniana), Mountain Everlasting (Antennaria dioica), Common Spotted-orchid (Dactylorhiza fuchsii), Early Marsh-orchid (D. incarnata), Frog Orchid (Coeloglossum viride) and Autumn Lady's-tresses (Spiranthes spiralis).Embryonic dunes, with characteristic species, including Sand Couch (Elymus farctus),occur at the southern end of the sand spit at Rosses Point. Sand dune habitats are rare and threatened in Europe and three types found on the site, embryonic dunes, Marram (Ammophila arenaria) dunes and fixed dunes, are listed on Annex I of the E.U. Habitats Directive, the last-named with priority status.

Wetlands on the site include Doonweelin Lake, a freshwater lake on the Rosses Point peninsula, which supports interesting vegetation communities that reflect the

Appendix B B18

juxtaposition of the underlying acidic and basic rocks. Ardtermon Fen, a small, floristically-rich area of freshwater marsh, swamp, wet grassland and fen is situated at the back of the Yellow Strand sandhills.

The site includes small areas of Hazel (Corylus avellana) and Ash (Fraxinusexcelsior) woodland on limestone (e.g. Cummeen Wood) and several other stands of mixed woodland and wet Willow (Salix spp.) woodland (as at Ardtermon Fen).

Cliff-top grassland is common in the north-western part of the site. This is dominated by Red Fescue (Festuca rubra) and White Clover (Trifolium repens), with associated species including Daisy (Bellis perennis), Common Bird's-foot-trefoil (Lotuscorniculatus), Plantains (Plantago coronopus, P. lanceolata and P. maritima),Bulbous Buttercup (Ranunculus bulbosus), Common Scurvygrass (Cochleariaofficinalis), Field Wood-rush (Luzula campestris) and Spring Sedge (Carexcaryophyllea).

The site has a good example of petrifying springs with tufa formations, with several species of bryophyte typical of the Cratoneurion. The springs occur along seepage zones in clay sea cliffs on the northern side of Sligo Harbour. Petrifying springs are listed with priority status on Annex I of the EU Habitats Directive.

The site has a very rich and diverse flora, on account of the wide variety of habitats found, and the presence of both basic and acidic substrates. Several rare, Red Data Book species have been recorded from the site, i.e. Rough Poppy (Papaver hybridum)which is also listed under the Flora (Protection) Order, 1999, Hoary Whitlowgrass (Draba incana) and Yellow Saxifrage (Saxifraga aizoides).

Both Drumcliff Bay and Cummeen Strand are important for the large numbers of waterfowl which use them in autumn/winter, including Ringed Plover, Redshank, Lapwing, Knot, Bar-tailed Godwit, Oystercatcher, Curlew, Golden Plover, Dunlin, Turnstone, Brent Goose, Grey Heron, Teal, Wigeon, Mallard, Shelduck and Red-breasted Merganser. The fields at Lissadell and Ballintemple support one of the largest populations of Barnacle Goose in the country (c2000 in winters of 1995/96 and 1996/97). Both Drumcliff Bay and Cummeen Strand have been designated as Special Protection Areas under the EU Birds Directive. The important feeding site for Barnacle Geese at Lissadell is a Statutory Nature Reserve.

The islands in the north-western section of the site hold important seabird colonies. A Cormorant colony of national importance occurs on Ardboline and Horse Islands, with a total of 261 pairs in 1998. Herring Gull and Great Black-backed Gull also breed on both islands. Common Tern formerly bred on both islands. The islands are also used by Barnacle Geese from the adjacent mainland, which roost or seek refuge here. The low sea cliffs on the adjacent mainland at Ballyconnell and Roskeeragh Points also support small numbers of seabirds and both Black Guillemot and Fulmar nest. Choughs feeds in the sandy/grassy areas of the site and one pair is known to nest. Several of the bird species that use the site are listed on Annex I of the EU Birds Directive, i.e. Barnacle Goose, Chough, Golden Plover and Bar-tailed Godwit.

Appendix B B19

At least five species listed on Annex II of the EU Habitats Directive are found within this site. Drumcliff Bay is important for the presence of a breeding population of Common Seal. Ardboline and Horse Islands on the western side of the site are also important as haul-out areas for this species. A minimum population of 12-15 individuals was estimated from counts made in various month in 2007 and 2008. Sea Lamprey and River Lamprey have been recorded in the Garavogue River, and River Lamprey are also known from further upstream in the tributaries of Lough Gill. The Marsh Fritillary butterfly is found at Rosses Point, while the rare snail, Vertigoangustior has recently been recorded from sand dunes at Killaspugbrone.

Cummeen Strand/Drumcliff Bay (Sligo Bay) is an important site of high conservation significance, which includes a wide variety of habitat types, including several listed on Annex I of the EU Habitats Directive, several species listed on Annex II of this directive, large and important populations of waterfowl and seabirds, and several rare plant species.

14.9.2010

Appendix B B20



STANDARD DATA FORM



AND


Start Form

NF000627

1

Appendix B B21





K IE0000627 199912

NATURA 2000 SITE CODES

IE0001994IE0002251


DATE SITE PROPOSED AS ELIGIBLE AS SCI:

199912

DATE CONFIRMED AS SCI:

DATE SITE CLASSIFIED AS SPA: DATE SITE DESIGNATED AS SAC:

1.7. SITE NAME:Cummeen Strand/Drumcliff Bay (Sligo Bay)


2

Appendix B B22



LONGITUDE LATITUDE

W

W/E (Greenwich)

8 31 48 54 19 21


4919.12

2.4. ALTITUDE (M):

0


33 5

2. SITE LOCATION





IE011 Border 20

8Marine area not covered by a NUTS-region

3

Appendix B B23






GLOBAL ASSESSMENT

1140 46 A A B A1130 14 A B B A5130 1 C C C C7220 1 B C B B2110 1 B C B B2130 1 C C C C2120 1 C C C C

4

Appendix B B24


3.2. SPECIES


and

and



5

Appendix B B25








Breed Winter Stage

2000 iBranta leucopsisA045 A A C A419 iPluvialis

apricariaA140 C B C

327 iLimosa lapponicaA157 C A C1 pPyrrhocorax

pyrrhocoraxA346 C B C




Breed Winter Stage

30+ pFulmarus glacialisA009 C C C261 pPhalacrocorax

carboA017 B A C A

395 iBranta berniclaA046 C A C A120 iTadorna tadornaA048 C A C750 iAnas penelopeA050 C A C250 iAnas creccaA052 C B C200 iAnas platyrhynchosA053 C B C48 iMergus merganserA070 C A C906 iHaematopus

ostralegusA130 C A C

118 iCharadriushiaticula

A137 C A C

77 iPluvialissquatarola

A141 C A C

1238 iVanellus vanellusA142 C B C1405 iCalidris alpinaA149 C A C750 iNumenius arquataA160 C B C562 iTringa totanusA162 B A C18 iTringa nebulariaA164 B A C




Breed Winter Stage6

Appendix B B26






Breed Winter Stage

86+ iPhoca vitulina1365 B A C A




Breed Winter Stage

pVertigo angustior1014 B B A

7

Appendix B B27





GROUP

P Draba incana p AP Orobanche hedera p A

B Cepphus grylle 10 i CB Somateria mollissma 2 p C

A Rana temporaria p AA Rana temporaria p C

M Lepus timidus hibernicus p AM Lepus timidus hibernicus p BM Lepus timidus hibernicus p CM Meles meles p AM Meles meles p C

8

Appendix B B28


4. SITE DESCRIPTION



Marine areas, Sea inlets 20

Tidal rivers, Estuaries, Mud flats, Sand flats, Lagoons (including saltwork basins)

60

Salt marshes, Salt pastures, Salt steppes 1

Coastal sand dunes, Sand beaches, Machair 3

Shingle, Sea cliffs, Islets 4Inland water bodies (Standing water, Running water) 1

Bogs, Marshes, Water fringed vegetation, Fens 1Heath, Scrub, Maquis and Garrigue, Phygrana 1

Dry grassland, Steppes 2

Humid grassland, Mesophile grassland 1Improved grassland 3Broad-leaved deciduous woodland 1

Artificial forest monoculture (e.g. Plantations of poplar or Exotic trees)

1

Other land (including Towns, Villages, Roads, Waste places, Mines, Industrial sites)

1


Other site characteristicsThis large coastal site is made up largely of two estuarine bays, Sligo Harbour and Drumcliff Bay. These are the estuaries of the Garavoge and Drumcliff rivers respectively. The estuaries are well sheltered and have extensive intertidal sand and mud flats. Coney Island provides the main shelter for Sligo Harbour, while a sandy/grassy spit protrudes from the Rosses peninsula and provides shelter for inner Drumcliff Bay. The site continues to the north-west of Drumcliff Bay to include the shallow marine waters of Brown’s Bay. A series of small islands, notably Ardbolin, occur here. Other coastal habitats are represented, including sand dunes, salt marshes, sandy and boulder beaches, and bedrock shoreline. In addition, there is a scattering of dry grassland, wet grassland, swamp vegetation and broad-leaved woodland. Improved grassland is included for the benefit of wintering geese. The site is largely underlain by Carboniferous limestone, but acidic rocks are also found at Rosses Point. An excellent series of fossilised corals occur at Serpent Rock in the north west of the site. The town of Sligo, a substantial urban centre with a regional port, is located along the eastern boundary of the Sligo Harbour section of the site.Agriculture is the dominant landuse in the surrounding catchments.

4.2. QUALITY AND IMPORTANCE:The estuarine and intertidal sand and mud flat habitats at this site are extensive in area, generally of good quality and show a good diversity of species and biotopes. Zostera spp. occur. These habitats are considered typical for the north-west region. The fixed dunes and shifting Ammophila dunes are small in area and only of moderate quality, though embryonic dunes are well represented.The site has a good example of petrifying springs with tufa formations, with several species of bryophyte typical of the Cratoneurion. The springs occur along seepage zones in clay sea cliffs. The site supports an area of Juniper scrub. The site has a nationally important colony of Phoca vitulina. Site is important for occurrence of the Annex II mollusc Vertigo angustior. A good diversity of waterfowl winter at site, notably internationally important populations of Branta leucopsis and Branta bernicla hrota. Site has regular

9

Appendix B B29


populations of Pluvialis apricaria and Limosa lapponica, both Annex I Bird Directive species, and eight other species winter in nationally important numbers. Phalacrocorax carbo has a nationally important breeding colony and small numbers of other breeding seabirds occur.

4.3. VULNERABILITYThe main activities affecting the estuarine and intertidal sand and mud flat habitats are pollution and aquaculture. Sewage, largely untreated, currently enters the site from Sligo town. A new treatment works is to be built which will significantly lessen this problem. Shellfish farming occurs at both Sligo Harbour and Drumcliff Bay on a large scale. While such activities cause localised disturbance to sediments and to wintering birds, all aquaculture applications are now assessed by Duchas to minimise impacts. Owing to growth of Sligo town, reclamation of estuarine habitat is a threat. The sand dune systems are subject to natural erosion which is exacerbated by intense recreational pressures. A significant area of dune has already been developed as a golf course.


4.5. OWNERSHIPState : Department of the Marine

State : Department of Arts, Heritage, Gaeltacht and the Islands

Local Authority : Sligo County Council

Semi-state : Coillte

Private : multiple

4.6. DOCUMENTATIONBowman, J.J., Clabby, K.J., Lucey, J., Mc Garrigle, M.L. and Toner, P.H. (1996). Water Quality in Ireland 1991-1994. Environmental Protection Agency, Wexford.

Cawley, M. (1996). Notes on some non-marine mollusca from Co Sligo and Co Leitrim, including a new site for Vertigo geyeri Lindholm. Irish Naturalists’ Journal 25: 183-185.

Colhoun, K. (1998). I-WeBS Report 1996-97. BirdWatch Ireland, Dublin.

Curtis, T.G.F. and Sheehy Skeffington, M.J. (1998). The salt marshes of Ireland: an inventory and account of their geographical variation. Biology and the Environment, Proceedings of the Royal Irish Academy 98B: 87-104.

Curtis, T.G.F. (1991a). A site inventory of the sandy coasts of Ireland. In Quigley, M.B. (ed.) A Guide to the Sand Dunes of Ireland. E.U.C.C. Dublin.

Curtis, T.G.F. (1991b). The flora and vegetation of sand dunes in Ireland. In Quigley, M.B. (ed.) A Guide to the Sand Dunes of Ireland. E.U.C.C., Dublin.

Falvey, J.P., Costello, M.J. and Dempsey, S. (1997). Survey of Intertidal Biotopes in Estuaries in Ireland. Unpublished report to the National Parks and Wildlife Service, Dublin.


Jennings O’Donovan & Partners (1998). Sligo Main Drainage Waste Water Treatment Works. Environmental Impact Statement, Main Report Volumes 1 and 2. Report prepared for Sligo Corporation.

10

Appendix B B30


Lockley, R.M. (1966). The distribution of grey and common seals on the coasts of Ireland. Irish Naturalists’ Journal 15: 136-143.

Lloyd, C. (1982). Inventory of Seabird Breeding Colonies in Republic of Ireland, Unpublished report, Forestry and Wildlife Service, Dublin.

Merne, O.J. (1989). Important bird areas in the Republic of Ireland. In: Grimmett, R.F.A. and Jones, T.A. (eds) Important Bird Areas in Europe. ICBP Technical Publication No. 9., Cambridge.

Moorkens, E.A. (1997). An Inventory of Mollusca in Potential SAC Sites, with Special Reference to Vertigo angustior, V. moulinsiana and V. geyeri.Unpublished report, National Parks & Wildlife Service, Dublin.

Praeger, R.L. (1934). The Botanist in Ireland. Hodges, Figgis & Co, Dublin.

Sheppard, R. (1993). Ireland’s Wetland Wealth. IWC, Dublin.

Summers, C.F., Warner, P.J., Nairn R.G.W., Curry, M.G. and Flynn, J. (1980). An assessment of the status of the common seal (Phoca vitulina vitulina) in Ireland. Biological Conservation 17: 115-123.

Warner, P. (1983). An assessment of the breeding populations of common seal (Phoca vitulina vitulina L.) in the Republic of Ireland during 1979. Irish Naturalists’ Journal 21: 24-26.

Warner, P. (1984). Report on the Census of Common Seals (Phoca vitulina vitulina) in the Republic of Ireland during 1984. Unpublished document to the Forest & Wildlife Service, Dublin.

Cronin, M., Duck, C., Ó Cadhla, O., Nairn, R., Strong, D. and O'Keeffe, C.(2004). Harbour seal population assessment in the Republic of Ireland: August 2003. Irish Wildlife Manuals No. 11. National Parks & Wildlife Service, Department of Environment, Heritage and Local Government., 7 Ely Place, Dublin 2, Ireland. 34 pp.�

Cronin, M., Duck, C., Ó Cadhla, O., Nairn, R., Strong, D. and O'Keeffe, C.(2007). An assessment of harbour seal population size and distribution in the Republic of Ireland during the 2003 moult season. J. Zool. Lond. 273 Issue 2: 131-139.�

Harrington, R. (1990). 1989 survey of breeding herds of common seal Phoca vitulina with reference to previous surveys. Report to the National Parks & Wildlife Service. 10pp.

�Lyons, D.O. (2004). Summary of National Parks & Wildlife Service surveys for common (harbour) seals (Phoca vitulina) and grey seals (Halichoerus grypus), 1978 to 2003. Irish Wildlife Manuals No. 13. National Parks & Wildlife Service, Department of Environment, Heritage and Local Government, 7 Ely Place, Dublin 2, Ireland. 67pp.

Roderick, T. (2009). Seal counts from Drumcliff Bay. Unpublished National Parks & Wildlife Service data, June 2007 - May 2008�

11

Appendix B B31








CODE % COVER

IE01 1IE05 24

TYPE CODE SITE NAME OVERLAP TYPE % COVER

IE01 Ballygilgan, Lissadell, Nature Reserve + 1IE05 Drumcliff Bay (part) Wildfowl Sanctuary * 24


800000466800000473800000476

12

Appendix B B32







CODE INTENSITY % OF SITE INFLUENCE120 2A B C + 0 -120 1A B C + 0 -140 3A B C + 0 -140 3A B C + 0 -160 1A B C + 0 -200 10A B C + 0 -211 10A B C + 0 -220 30A B C + 0 -230 30A B C + 0 -301 1A B C + 0 -420 60A B C + 0 -505 1A B C + 0 -622 5A B C + 0 -870 2A B C + 0 -900 10A B C + 0 -

CODE INTENSITY INFLUENCE120 A B C + 0 -400 A B C + 0 -410 A B C + 0 -601 A B C + 0 -



National Parks and Wildlife is responsible for managing the Ballygilgan Nature Reserve, and for maintaining the Drumcliff Bay Wildfowl Sanctuary as a No-shooting Area.

A management plan for the entire site is in preparation.

Ballygilgan Nature Reserve is managed for the benefit of Branta leucopsis and other waterfowl species. A hide and interpretative panels exist. The goose population is monitored by Duchas staff.

The Drumcliff Wildfowl Sanctuary is patrolled by Duchas staff so as to prevent shooting.

13

Appendix B B33


7. MAPS OF THE SITE

- Physical map


8. SLIDES

NUMBER AREA SUBJECT DATE

0207041 Sligo Harbour - Drumcliff Bay

Overview of Site 199506

0207045 Sligo Harbour - Drumcliff Bay

Overview of Site - Outer Party 199506

14

Appendix B B34

Generic Conservation Objective18 July 2011

Conservation Objectives for Lough Gill SAC [001976]

European and national legislation places a collective obligation on Ireland and its citizens tomaintain habitats and species in the Natura 2000 network at favourable conservationcondition. The Government and its agencies are responsible for the implementation andenforcement of regulations that will ensure the ecological integrity of these sites.



Objective: To maintain or restore the favourable conservation condition of the Annex Ihabitat(s) and/or the Annex II species for which the SAC has been selected:



Start 001976

Austropotamobius pallipes[1092]Petromyzon marinus[1095]Lampetra planeri[1096]Lampetra fluviatilis[1099]Salmo salar (only in fresh water)[1106]Lutra lutra[1355]Natural eutrophic lakes withMagnopotamion or Hydrocharition type vegetation[3150]Old sessile oak woods with Ilex and Blechnum in the British Isles[91A0]* Alluvial forests with Alnus glutinosa and Fraxinus excelsior (Alno Padion, Alnion incanae, Salicionalbae)

[91E0]


NPWS (2011) Conservation objectives for Lough Gill SAC [001976]. Generic Version 3.0. Department of Arts,Heritage & the Gaeltacht.

Citation:

Appendix B B35

SITE SYNOPSIS

SITE NAME: LOUGH GILL

SITE CODE: 001976

This site comprises Lough Gill with Doon Lough to the north-east, the Bonet River asfar as but not including Glenade Lough, and a stretch of the Owenmore River nearManorhamilton in Co. Leitrim. Lough Gill itself, 2 km east of Sligo town, lies at ageological junction of ancient metamorphic rocks which produce acid groundwater,and limestone which dissolves in the groundwater. The large 8 km long lake hassteep limestone shores and underwater cliffs and is over 20m deep in places. The lakeappears to be naturally eutrophic, and thus represents a habitat listed on Annex I ofthe EU Habitats Directive.

The site is a candidate SAC selected for alluvial wet woodlands a priority habitat onAnnex I of the E.U. Habitats Directive. The site is also selected as a candidate SACfor old Oak woodlands and natural eutrophic lakes, both habitats listed on Annex I ofthe E.U. Habitats Directive. The site is also selected for the following species listedon Annex II of the same directive - Sea Lamprey, River Lamprey, Brook Lamprey,White-clawed Crayfish, Atlantic Salmon and Otter.

The aquatic macrophyte flora is very limited, probably due to the rapid increase indepth around most of the margin. Species such as pondweeds (Potamogeton spp.) arepresent, as well as Shoreweed (Littorella uniflora). Where the lake shore has ashallow gradient, some swamp vegetation occurs, mainly dominated by CommonReed (Phragmites australis), with Common Club-rush (Scirpus lacustris) and sedges(Carex spp.).

The site contains Old Oak Woodlands, a habitat listed on Annex I of the EU HabitatsDirective. These woods are dominated by Oak (Quercus spp.), Rowan (Sorbusaucuparia) and Willows (Salix spp.). Strawberry Tree (Arbutus unedo), in its mostnortherly site in the world, Yew (Taxus baccata), in abundance, Bird Cherry (Prunuspadus), a Red Data Book species, and the nationally scarce Rock Whitebeam (Sorbusrupicola) can also be found here. Some areas of conifer plantation occur inassociation with these woodlands. The site is also notable for the presence of AlluvialForest, a priority habitat listed on Annex I of the E.U. Habitats Directive, which isfound along the banks of the Garvoge River and at the mouth of the Bonet River.These wet woodlands are dominated by Alder (Alnus glutinosa) and Willows.

Areas of unimproved wet and dry grassland occur within the site, the formerparticularly by the lake and the latter well developed in the north-east of the site andin the vicinity of O’Rourke’s Table.

Heath-covered hillsides above the woods are dominated by Heather (Callunavulgaris). Both the woods and the mountains are used by a large herd of Fallow Deer.

Appendix B B36

The site is of considerable importance for the presence of four Red Data Book fishspecies that are listed on Annex II of the E.U. Habitats Directive - Brook Lamprey(Lampetra planeri), River Lamprey (Lampetra fluviatilis), Sea Lamprey (Petromyzonmarinus) and Atlantic Salmon (Salmo salar). The Lough Gill system gets a veryearly run of spring salmon while the Bonet holds stocks of salmon from spring rightthrough to the end of the season.

White-clawed Crayfish (Austropotamobius pallipes), Otter and Pine Marten are wellestablished on this site, the former, both being Annex II species. The woodlands havea fauna which includes several rare snail species.

The site supports several rare plant species, including Yellow Bird's-nest (Monotropahypopitys), Lady’s Mantle (Alchemilla glaucescens), Ivy Broomrape (Orobanchehederae), Black Bryony (Tamus communis), Intermediate Wintergreen (Pyrolamedia) and Bird's-nest Orchid (Neottia nidus-avis). There is also an unconfirmedrecord for Melancholy Thistle (Cirsium helenioides) from the eastern side of the site.

Lough Gill supports only low numbers of wintering waterfowl, mostly Mallard(<150), Tufted Duck (20-30) and Goldeneye (<20). A small colony of CommonTerns breed on the islands (20 pairs in 1993), while Kingfishers are found on the lakeand rivers. Both of these species are listed on Annex I of the E.U. Birds Directive. Acolony of Black-headed Gulls (63 pairs in 1992) occurs with the terns. The woodssupport a good diversity of bird species including Jay, Woodcock and Blackcap.

The site is of importance for three habitats listed on Annex I of the E.U. HabitatsDirective, including one with priority status. It is also noted for the high number ofrare or scarce animal and plant species. Detailed ecological studies have been carriedout on the lake in recent years and a management plan for Lough Gill catchment wasproduced in 1998 for Sligo County Council.

6.10.2006

Appendix B B37



STANDARD DATA FORM



AND


Start Form

NF001976

1

Appendix B B38





B IE0001976 199908


DATE SITE PROPOSED AS ELIGIBLE AS SCI:

199908

DATE CONFIRMED AS SCI:

DATE SITE CLASSIFIED AS SPA: DATE SITE DESIGNATED AS SAC:

1.7. SITE NAME:Lough Gill


2

Appendix B B39



LONGITUDE LATITUDE

W

W/E (Greenwich)

8 18 30 54 16 54


3320.45

2.4. ALTITUDE (M):

7


122 10

2. SITE LOCATION





IE011 Border 100

3

Appendix B B40






GLOBAL ASSESSMENT

3150 78 B B B B91a0 3 B C C B91e0 1 B B B B

4

Appendix B B41


3.2. SPECIES


and

and



5

Appendix B B42










Breed Winter Stage

20 pSterna hirundoA193 C B C2 pAlcedo atthisA229 C B C




Breed Winter Stage

63 pLarus ridibundusA179 C B C19 iBucephala clangulaA067 C C C23 iAythya fuligulaA061 C C C128 iAnas platyrhynchosA053 C B C




Breed Winter Stage

PLutra lutra1355 C A C

6

Appendix B B43







Breed Winter Stage

pPetromyzon marinus1095 C B CpLampetra planeri1096 C B C

pLampetrafluviatilis

1099 C B C

cSalmo salar1106 C B C




Breed Winter Stage

pAustropotamobiuspallipes

1092 C B C

7

Appendix B B44





GROUP

B Cygnus olor 6 p CP Prunus padus p AP Pyrola media p AP Pseudorchis albida p AP Arbutus unedo p D

A Rana temporaria p AA Rana temporaria p CA Triturus vulgaris p C

R Lacerta vivipara p CM Meles meles p AM Meles meles p CM Martes martes p AM Martes martes p CM Mustela erminea hibernicus p CM Sciurus vulgaris p C

I Acicula fusca p DI Spermodea lamellata p DI Ena obscura p DI Limax cinereoniger p DI Marpessa laminata p DI Zenobiella subrufescens p DI Coenagrion lunulatum p DI Celastrina argiolus p DI Quercusia quercus p DI Callophrys rubi p DI Leptidea sinapis p DI Erynnis tages p D

M Mustela erminea hibernicus p B

8

Appendix B B45


4. SITE DESCRIPTION



Inland water bodies (Standing water, Running water) 80

Bogs, Marshes, Water fringed vegetation, Fens 3Heath, Scrub, Maquis and Garrigue, Phygrana 4

Dry grassland, Steppes 1Humid grassland, Mesophile grassland 2

Broad-leaved deciduous woodland 8

Artificial forest monoculture (e.g. Plantations of poplar or Exotic trees)

1

Inland rocks, Screes, Sands, Permanent Snow and ice 1


Other site characteristicsLough Gill is a moderate to large sized lake lying immediately east of Sligo town. It is fed by the River Bonet and drains into the sea via the Garvogue River, a short, wide and slow flowing river which passes through Sligo town.The lake lies along the junction between old metamorphic rocks to the south and limestone to the north. The water of the lake is thus influenced by both acidic and alkaline inputs, although nearly all the basin lies over limestone. The lake is 8 km by 2-3 km and has an area of 1,400 ha. It is a deep lake, with maximum depth at 31 m. Islands are a feature of the lake. Much of the shoreline is wooded and there is also some swamp vegetation, wet grassland and scrub along the shoreline. The lake is an important salmonid and coarse fishery and is used for a range of recreational activities. The site also includes the Shanvans and Owenmore rivers.

4.2. QUALITY AND IMPORTANCE:An important example of a lake which appears to be naturally eutrophic. Quality generally good though blooms of blue-green algae in recent years indicate some artificial enrichment. Significant areas of alluvial forest occur along the Garvoge River (Osmunda - Salicetum atrocinerea type) and at the mouth of the River Bonet (Carici remotae - Fraxientum type). Old oak woodland of varying quality is well scattered along the shoreline and on some of the islands and is an important example of this habitat for western Ireland. At least six Red Data Book plant species have been recorded from site. Site has three species of lamprey and Austropotamobius pallipes. The lake and its associated rivers support an important population of Salmo salar. Lutra lutra has a good population within the site. Of minor importance for birds though the site has a small breeding colony of Sterna hirundo. A wide range of rare or scarce invertebrates are known from the site, as well as several Red Data Book mammal species, including Martes martes.

4.3. VULNERABILITYEutrophication, mostly as a result of agricultural activities in the catchment, is the main threat to water quality in the lake. A proposed water supply scheme

9

Appendix B B46


for Sligo and its environs would lead to changes in water levels. A detailed ecological assessment of the impacts of the scheme has been carried out and the most vulnerable habitats and taxa identified - the sensitivity of the alluvial forests was highlighted. Parts of the oak woods are seriously threatened by the invasive spread of non-native species, by interplanting with conifers, and by poor regeneration as a result of grazing pressures by feral deer. A catchment management plan has recently been produced and will be beneficial for the site.


4.5. OWNERSHIPLocal Authority: Sligo Corporation

Semi-state: Coillte Teorante

Private: Multiple

State: L.Gill

4.6. DOCUMENTATIONCentral Fisheries Board (2001). Irish Salmon Catches 2000.http://www.cfb.ie/:February 2001.

Clabby, K.J., Lucey, J., McGarrigle, M.L., Bowman, J.J., Flanagan, P.J. and Toner, P.F. (1992). Water Quality in Ireland 1987-1990. Part One General Assessment. Environmental Research Unit, Dublin.

Cotton, D.C.F. (1982). Coenagrion lunulatum (Charpentier) (Odonata: Coenagridae) new to the British Isles. Entomologists’ Gazette 33: 213-214.

Cotton, D.C.F. (1993). Ecological Study of Lough Gill - to Predict the Effects of the Sligo and Environs Water Supply Scheme on the Flora and Fauna with Suggestions for Future Management. Report prepared in conjunction with Jennings O’Donovan and Partners for Sligo County Council.

Cotton, D.C.F. and Cawley, M. (1993). New records for vascular plants from Cos. Sligo (H28) and Leitrim (H29). Irish Naturalists’ Journal 24: 288-295.

Colhoun, K. (1998). I-WeBS Report 1996-97. BirdWatch Ireland, Dublin.

Doris, Y., McGarrigle, M.L., Clabby, K.J., Lucey, J., Neill, M., Flanagan, M., Quinn, M.B., Sugrue, M. and Lehane, M. (1999). Water Quality in Ireland 1995-1997. Statistical Compendium of River Quality Data. Electronic Publication on Disk. Environmental Protection Agency, Wexford.

Flanagan, P.J. and Toner, P.F. (1975). A preliminary survey of Irish lakes. An Foras Forbartha, Water Resources Division.


Jennings O’Donovan and Partners (1994). Sligo and Environs Water Supply Scheme. Ecology Study. Report prepared for Sligo County Council.

Kelly, D.L. and Iremonger, S.F. (1997). Irish wetland woods: the plant communities and their ecology. Biology and Environment - Proceedings of the Royal Irish Academy 97B: 1-32.

Kurz, I. and Costello, M.J. (1998). An Outline of the Biology, Distribution & Conservation of Lampreys in Ireland. Irish Wildlife Manual No. 5 Dúchas The Heritage Service.

O'Reilly, P. (1991). Trout and Salmon Rivers of Ireland: an Anglers Guide.Merlin Unwin Books, London.

10

Appendix B B47


Praeger, R.L. (1932). Some noteworthy plants found in or reported from Ireland. Proceedings of the Royal Irish Academy 41B (4): 95-124.

Praeger, R.L. (1934). The Botanist in Ireland. Hodges & Figgis, Dublin.

Round, F.E. and Brook, A.J. (1959). The phytoplankton of some Irish loughs and an assessment of their trophic status. Proceedings of the Royal Irish Academy 60B (4): 167-191.

Thompson, E., Ryan, S. and Cotton, D.C.F. (1998). Management Plan for the Lough Gill Catchment. Sligo County Council.

Whilde, A. (1985). The All Ireland Tern Survey 1984. Unpublished report for the Irish Wildbird Conservancy, Dublin.

Whilde, A., Cotton, D.C.F., and Sheppard, R. (1993). A repeat survey of gulls breeding in Counties Donegal, Sligo, Mayo and Galway, with recent counts from Leitrim and Fermanagh. Irish Birds 5: 67-72.

11

Appendix B B48









800000471

12

Appendix B B49







CODE INTENSITY % OF SITE INFLUENCE140 1A B C + 0 -160 2A B C + 0 -210 70A B C + 0 -220 70A B C + 0 -622 20A B C + 0 -890 80A B C + 0 -952 80A B C + 0 -954 5A B C + 0 -

CODE INTENSITY INFLUENCE120 A B C + 0 -140 A B C + 0 -160 A B C + 0 -400 A B C + 0 -403 A B C + 0 -810 A B C + 0 -



A management plan for the conservation of this site is in preparation

13

Appendix B B50


7. MAPS OF THE SITE

- Physical map


8. SLIDES

NUMBER AREA SUBJECT DATE

O227122 Lough Gill Western and central parts 199506O227123 Lough Gill Central and eastern parts 199506

14

Appendix B B51

Appendix B B52

NIS Appendix C

APPENDIX C – BENTHIC FAUNA SPECIES LIST, AQUAFACT FIELDWORK 2010

(on accompanying DVD)

NIS Appendix C

NIS Appendix D D1

APPENDIX D – IRISH WHALE AND DOLPHIN GROUP SIGHTINGS TABLES – SLIGO AREA

Date Species Animals Location

12 Sep 2009 bottlenose dolphin 7 Sligo Bay, Sligo

25 Jun 2009 bottlenose dolphin 30 Sligo Bay, Sligo

10 May 2009 bottlenose dolphin 4 Sligo Bay, Sligo

8 Nov 2008 harbour porpoise 2 Sligo Bay, Sligo

2 Aug 2008 bottlenose dolphin 1 Sligo Bay, Sligo

19 Jan 2008 harbour porpoise 1 Sligo Bay, Sligo

11 Jul 2007 harbour porpoise 2 Sligo Bay, Sligo

17 Jul 2002 bottlenose dolphin 4 Sligo Bay, Sligo

4 Aug 1995 "dolphin" species, possibly harbour porpoise 4 Sligo Bay, Sligo

13 Jul 1995 bottlenose dolphin 4 Sligo Bay, Sligo

13 Jun 1988 common dolphin 20 Sligo Bay, Sligo


2 Jun 2010 "dolphin" species 4 Drumcliff, Sligo

22 Jul 2004 bottlenose dolphin 6 Drumcliff, Sligo


16 Aug 2010 bottlenose dolphin 12 Rosses Point, Sligo

6 Jul 2002 "dolphin" species 30 Rosses Point, Sligo

1 May 2002 bottlenose dolphin 20 Rosses Point, Sligo

8 Apr 1988 common dolphin 40 Rosses Point, Sligo


5 Sep 2010 bottlenose dolphin 2 Strandhill, Sligo

26 Jun 2010 harbour porpoise 4 Strandhill, Sligo

8 Aug 2008 "dolphin" species, possibly harbour porpoise 4 Strandhill, Sligo

29 Jul 2008 harbour porpoise 5 Strandhill, Sligo

28 May 2008 harbour porpoise 2 Strandhill, Sligo

27 May 2008 "dolphin" species, possibly harbour porpoise 3 Strandhill, Sligo

8 Aug 2007 "dolphin" species 25 Strandhill, Sligo

12 Oct 2004 harbour porpoise 3 Strandhill, Sligo

10 Sep 2004 harbour porpoise 10 Strandhill, Sligo

9 Sep 2004 "dolphin" species, possibly harbour porpoise 30 Strandhill, Sligo

NIS Appendix D D2


8 Sep 2004 "dolphin" species, possibly harbour porpoise 10 Strandhill, Sligo



17 Aug 2004 harbour porpoise 2 Strandhill, Sligo

16 Aug 2004 bottlenose dolphin 6 Strandhill, Sligo

11 Aug 2004 harbour porpoise 4 Strandhill, Sligo


5 Jun 2010 bottlenose dolphin 3 Ballyconnell, Sligo

14 Jun 2009 harbour porpoise 6 Ballyconnell, Sligo

13 Jul 2002 "dolphin" species, possibly harbour porpoise 13 Ballyconnell, Sligo


3 Jun 2008 basking shark 1 Ballysodare Bay, Sligo

28 Jul 2004 harbour porpoise 3 Ballysodare Bay, Sligo

10 Jun 2004 bottlenose dolphin 4 Ballysodare Bay, Sligo


3 Jun 2008 basking shark 1 Ballysodare Bay, Sligo

28 Jul 2004 harbour porpoise 3 Ballysodare Bay, Sligo

10 Jun 2004 bottlenose dolphin 4 Ballysodare Bay, Sligo


16 Oct 2010 bottlenose dolphin 10 Dunmoran Strand, Sligo

26 Aug 2009 large fin 2 Dunmoran Strand, Sligo

24 Sep 2008 bottlenose dolphin 3 Dunmoran Strand, Sligo

24 Jun 2006 bottlenose dolphin 12 Dunmoran Strand, Sligo

17 Aug 2002 "whale" species 1 Dunmoran Strand, Sligo

26 Dec 1988 bottlenose dolphin 15 Dunmoran Strand, Sligo

18 Sep 1988 bottlenose dolphin 17 Dunmoran Strand, Sligo


30 May 2008 basking shark 1 Lisadell, Sligo

21 Sep 2005 bottlenose dolphin 7 Lisadell, Sligo

20 Sep 2005 bottlenose dolphin 3 Lisadell, Sligo

NIS Appendix D D3

16 May 2003 harbour porpoise 2 Lisadell, Sligo


16 Nov 1995 "cetacean" species 7 Long Rock, Sligo


16 May 2009 "dolphin" species 2 Portavaud, Sligo

22 Oct 1983 "dolphin" species, possibly harbour porpoise 30 Portavaud, Sligo


2 Aug 2010 harbour porpoise 1 Raugley, Sligo

NIS Appendix D D4

Appendix E E1

APPENDIX E – ECIA CRITERIA

Table (i) Ecological site evaluation criteria (derived from NRA and IEEM EcIA

guidelines)

Table (ii) NRA EcIA criteria for assessing impact magnitude (and glossary of impacts) Table (i) Ecological Site Evaluation Criteria (derived from NRA and IEEM EcIA Guidelines)

Ecological value Criteria

Internationally Important (A sites)

EU Annex habitat in an internationally designated

conservation area (or qualifying site; or site with a

proposed designation)

A viable area of a habitat type listed in Annex I of

the Habitats Directive, or smaller areas of such

habitat which are essential to maintain the viability

of a larger whole.

Non-designated high quality habitat which equates

to an EU Annex I priority habitat

A regularly occurring, nationally significant

population / number of any internationally

important species.

Nationally Important (B sites)

EU Annex habitat in a designated (or proposed)

NHA.

Non-designated good example of Annex I habitat

(Under EU habitats Directive)

Any habitat which may have been formerly

classified as EU Annex I quality, but which has

been subsequently highly modified as a result of

change in the physical environment or damaged.

Such a habitat may be still be classified as an

Annex habitat on the basis of the presence of one

or more character plant species, but can no longer

be considered a good example of that habitat type

Locally important High value

(C sites)

Sites containing semi-natural habitat types with

high biodiversity in a local context, with high

degree of intrinsic naturalness.

Locally rare habitats or species

Moderate value

(D sites)

Sites containing some semi-natural habitat or

locally important for wildlife

Low value

(E sites)

Highly modified or artificial habitats with low

intrinsic ecological value in terms of biodiversity

Artificial habitats which provide some secondary

wildlife habitat of local value

Appendix E E2

Table (ii) NRA EcIA criteria for assessing impact magnitude

Impact

magnitude

Internationally

important *(A sites)

Nationally

important (B sites)

High value

locally important

(C sites)

Moderate value

locally important

(D sites)

Low value

locally important

(E sites)

Profound negative

Any permanent

impacts

Permanent

impacts on a

large part of a

site

Significant negative

Temporary

impacts on a

large part of a

site

Permanent

impacts on a

small part of a

site

Permanent

impacts on a

large part of a

site

Moderate negative

Temporary

impacts on a

small part of a

site

Temporary

impacts on a

large part of a

site

Permanent

impacts on a

small part of a

site

Permanent

impacts on a

small part of a

site

Permanent

impacts on a

site if part of a

designated site

Slight negative Permanent

impacts on a

small part of a

site

Temporary

impacts on a

large part of a

site

Permanent

impacts on a

small part of a

site

Permanent

impacts on a

large part of a

site

Imperceptible negative

Temporary

impacts on a

large part of a

site

Temporary

impacts on a

large part of a

site

Permanent

impacts on a

small part of a

site

Neutral No impacts No impacts No impacts No impacts No impacts

Slight positive Permanent

beneficial

impacts on a

small part of a

site

Permanent

beneficial

impacts on a

large part of a

site

For ecological evaluation criteria see Table (i) above

Appendix E E3

Glossary of impacts: Quality of Impacts Significance of impacts Duration of impacts Types of impacts

Positive Impact: a

change which improves the

quality of the environment

(for example by increasing

species diversity; or the

improving reproductive

capacity of an ecosystem; or

removing nuisances or

improving amenity)

Imperceptible impact: a

measurable impact without

noticeable consequences

Short-term impact:impact lasting one to seven

years

Cumulative impact: the

addition of many small impacts to

create one larger, more significant

impact

Neutral impact: a change

which does not affect the


Slight impact: an impact

which causes noticeable

changes in the character of

the environment without

affecting its sensitivities

Medium-term impact:impact lasting seven to fifteen

years

‘Do-nothing impact’: the

environment as it would be in the

future should no development of

any ind be carried out

Negative impact: a

change which reduces the


(for example lessening

species diversity; or

diminishing the reproductive

capacity of an ecosystem; or

damaging health or property

or by causing nuisance)

Moderate impact: an

impact which alters the

character of the environment

in a manners that is

consistent with existing and

emerging trends

Long-term impact: impact

lasting fifteen to sixty years

Indeterminable impact: when

the full consequences of a change

in the environment cannot be

described

Significant impact: an

impact which by its character,

magnitude, duration or

intensity alters a sensitive

aspect of the environment

Permanent impact:impact lasting over sixty

years

Irreversible impact: when the

character, distinctiveness,

diversity or reproductive capacity

of an environment is permanently

lost

Profound impact: an

impact which obliterates

sensitive characteristics

Temporary impact:impact lasting for one year or

less

Residual impact: the degree of

environmental change that will

occur after the proposed

mitigation measures have taken

affect

Synergistic impact: where the

resultant impact is of greater

significance than the sum of its

constituents

Worst case impact: the

impacts arising from a

development in the case where

mitigation measures substantially

fail

Appendix E E4

NIS Appendix F F1

APPENDIX F – HYDRODYNAMIC MODELLING CHAPTER OF ENVIRONMENTAL APPRAISAL

11. HYDRODYNAMIC MODELLING

Hydrodynamic modelling was undertaken to investigate the impact of the dredging

operations on Sligo Harbour. The modelling examines the effect of the dispersion and fate of

material put into suspension during the period of the dredging operations.

11.1. COMPUTATIONAL MODEL OF WATER INJECTION MAINTENANCE DREDGING OPERATIONS (5,500m³)

Hydrodynamic modelling was undertaken to investigate the impact of the maintenance

dredging by water injection dredger on Sligo Harbour. The modelling examines the effect of

the dispersion and fate of material put into suspension during the period of the dredging

operations.

11.1.1. Modelling Software

The computational models used in this study were based on the MIKE 21 coastal process

software which has been developed by the Danish Hydraulics Institute. The modules of this

coastal process modelling system used in this study comprised:

2D hydrodynamic flow models

Particle tracking models

11.1.2. Hydrodynamic Flow Model

The main hydrodynamic flow model used in the study was a 2D MIKE21 nested HD flow

model consisting of a 30m grid outer model and a finer 10m grid inner model. The extent of

the nested flow model is shown in Figure 40 below.

11.1.2.1. Dredged Spoil Dispersal Model

The dredged spoil disposal modelling was undertaken using the MIKE 321npa model. This is

a particle tracking model that uses the hydraulic flow regime from the MIKE21 nHD model to

simulate the transport and fate of material discharged to the water column. The model can

include variable graded material and takes effect of re-erosion of deposited sediment so it is

particularly suitable for the simulation of the dispersal of water injected sediments.

NIS Appendix F F2

Figure 40:Extent of 30 and 10 metre grid nested flow model

11.1.3. Bathymetry

The bathymetry for the model studies was taken from very detailed LiDAR and multi-beam

hydrographic surveys of the entire model area undertaken by the Geological Survey of

Ireland in 2008 under the INFOMAR project. These surveys comprised some 46 Gigabytes

of xyz data. A narrow beam hydrographic survey was undertaken of c.850m of the

navigation channel leading to the Deepwater Jetty in October 2011 (Figure 41) to provide

accurate data on the quantity of material to be dredged.

NIS Appendix F F3

Figure 41: Extent of LiDAR Bathymetry and 2011 Bathymetric Survey

11.1.4. Model Calibration

The models were calibrated against flow measurements undertaken in December 2009 using

two ADCP current meters, one deployed to the west of Deadman's Point and the other in the

channel to Drumcliff Bay. The model and current meter velocities were compared for tidal

conditions with the same tidal range and the model results were found to be consistent with

the field measurements.

11.1.5. Model Simulations

11.1.5.1. Tidal Flow Modelling

Model Tidal Flow Regime The tidal flow modelling was undertaken for a whole month of tides based on a typical period

31 January 2003 to 2 March 2003. The fresh water flow into Sligo harbour was set at 14.7

cumecs which was derived from the annual average flow for the catchments feeding into the

Garavogue River. The tidal curve at Oyster Island for the model period is shown in Figure 42.

NIS Appendix F F4

Figure 42: Tidal curve for 1 month simulation period.

The tidal modelling was undertaken for the existing bathymetry and for the bathymetry with

the proposed dredged channel completed. Typical flow patterns are shown in Figure 43 and

Figure 44; which illustrate mid flood and mid ebb tides respectively around Sligo harbour for

a spring tide.

Figure 43: Typical flow patterns in Sligo harbour - flood tide

NIS Appendix F F5

Figure 44: Typical flow patterns in Sligo harbour - ebb tide

11.1.6. Dredging Plume Simulation Modelling

11.1.6.1. Dredging Programme

The dredged plume modelling simulations were undertaken to provide information on the

dispersion and fate of dredged material discharged to the water column during the water

injection maintenance dredging of some 5,500 cubic metres of material required to clear the

approach channel to the Deepwater jetty and remove pockets of sediment from the berths at

both the Deepwater and the Barytes jetties.

The dredging will focus on 5 target sites within the dredging area outlined, as shown in

Figure 45, where the channel depth has become dangerously shallow.

A conservative approach has been taken to calculate the dredging impacts, using the “worst

case” impacts.

General information on the water injection dredging process has been obtained from

dredging contractors Van Oord, who have substantial experience in this field.

It is proposed that dredging will take place over a period of spring tides. The water depth

and current velocities in the channel are such that the dredger will only be able to work for

approximately 4.5 hours of every tidal cycle. Dredging operations will only occur on the

NIS Appendix F F6

ebbing tide in order to assist with the travel of the mobilised sediment away from the port

area.

The quantities involved (5,500m³) are relatively small. It is thought that the dredger will be

able to remove around 1,000m³ of sediment per tide, therefore it will take only around 5 or 6

tides to complete the operations. In order to take account of the length of time it may take for

particles put in to re-suspension during subsequent tides to settle out, the model has been

run for 28 days to present a complete picture of final dispersion and settlement patterns.

11.1.6.2. Flow Model Data

The dredging plume modelling was undertaken using the M321 npa particle tracking model

which simulates the transport and deposition of material discharged into the water column.

The model uses the data from the tidal model simulation as the basic hydrodynamic input to

the simulations.

11.1.6.3. Sediment Composition

As part of the sampling regime for the larger capital and maintenance dredge project

proposed within Sligo Harbour, 12 No. samples from the bottom sediments along the entire

5.2km length of the navigation channel were collected for physical, chemical and radiological

testing. The full results of this testing are presented in Attachment C.1 and C.2.

The location of the sampling stations in relation to the dredging area is shown in Drawing 4

It can be seen that Station Dr-5 is within the proposed Water Injection Maintenance Dredging

Area, whilst Stations Dr-4 and Dr-6 are approximately 150m upstream and downstream of

the Dredging Area respectively.

NIS Appendix F F7

Figure 45: Target areas (A-E) for maintenance dredging by Water Injection Dredging

Table 5: Dredging Area Sediment Samples – Descriptions Station ID

Location Colour Smell %Water

Dr-4 Channel c. 200m south east of dredging area boundary

WGS84 54° 16' 52.79" N

8° 29' 21.3" W

Grey/brown

Mud none 66.6

NIS Appendix F F8

ITM 568140, 837059

Dr-5 Inside dredging area

WGS84 54° 17' 1.93" N

8° 29' 32.86" W

ITM 567932, 837343

Grey/brown

Muddy sand none 54.4

Dr-6 Channel c. 200m north west of dredging area boundary

WGS84 54° 17' 9.89" N

8° 29' 41.78" W

ITM 567773, 837590

Grey/brown

Muddy/sand none 64.3

Table 6: Dredging Area Sediment Samples – Granulometry Results

Station Gravel

(>4 mm) C. Sand

(1 – 4mm)M. Sand

(0.5– 1mm) Fine Sand

(0.063-0.5 mm) Silt/Clay

(<0.063mm)

Dr-4 0 2.1 5.4 52.8 39.6

Dr-5 0 1.0 2.5 83.4 13.1

Dr-6 0.5 0.4 0.3 85.4 13.4

The information from the three samples shows that the material to be dredged is

predominantly a fine grey silty sand.

NIS Appendix F F9

Water Injection Dredging puts the seabed layer into suspension by injecting water into the

subsoil, thus fluidising it. This fluidised bottom layer, the thickness of which (typically

between 1m and 3m) is highly sensitive to both the soil parameters and the distance

between the injector pipe and the seabed ("stand-off distance"), then behaves as a density

current.

The low injector pressure (approx.1 bar) and keeping a small stand-off distance are key

factors in minimising turbidity. The optimum stand-off distance, which depends upon the

settled sediments’ particle size distribution and permeability, is often determined through

practical experience. The properties of the induced fluid mud layer depend on a large

number of factors, but of prime importance are the particle size and viscosity of the sediment.

The fate of the material being put into suspension by the dredger has been assessed using

the Mike 321 npa model. The model simulates the fate of the material from the dredger by

releasing particles into the water column at a source 0.5m above the bed and tracking each

particle throughout the simulation process. A range of grain sizes have been used in the

model, in order to cater for the sediment grading of the dredged material. The grading used

for the main source was based on the grading in the PSA results from the bed material

samples. This source had the distribution of grain size shown below.

11.1.6.4. Dredging Simulations

The dredging programme and tidal conditions were as noted in the above sections.

Dredging operations were assumed to be undertaken over 5 consecutive tides.

The simulations for the dredging were run for the full 28 day tidal sequence to give the

overall pattern of dispersion and deposition including the effects of particle re-suspension

from the whole of the dredging operation.

Grain Dia mm % Occurrence

0.375 6

0.187 62

0.090 20

0.050 7

0.030 5

NIS Appendix F F10

11.1.7. Results of the Dredging Simulations

11.1.7.1. Sediment Deposition The results of the water injection dredging simulations are shown graphically by a series of

model output diagrams. The figures show the sediment deposition depths during dredging

and at the completion of the dredging, as well as the peak and average envelope values for

the suspended sediment concentrations throughout the dredging.

The maximum deposition envelope diagram (Figure 46) represents the maximum value that

occurred at each grid point in the model at any time during the simulation period, even if the

period of the peak value is very short.

The maximum peak sediment deposition depth in mm can be roughly calculated by dividing

the kg/m² by a figure of 1.65. This shows that in the areas of the harbour coloured green, the

maximum peak deposition depth is c.4mm – 6mm. However, in some areas around the

training walls, peak deposition could reach c.24mm to 48mm.

However, it should be noted that these peak values are typically of a very short duration and

tend to occur as current speeds drop during slack tide. The material may then be raised into

suspension again and moved further from the dredging area as the tidal currents pick up

during the next tide.

This re-suspension will cause the final settlement pattern to be more defined (Figure 47),

with the dredged material settling around the training wall, in sheltered areas on the northern

shore of Cartron Marsh and some of being swept out of the harbour to settle on the Bungar

Bank and offshore from Rosses Point.

The pattern of residual sediment deposition following the completion of the dredging is

shown in Figure 47.

In general, deposition depths in these areas will be beneath 3.0mm with only very limited

areas receiving more than 10mm of deposition. Overall the amount of sediment deposition in

the harbour area on completion of water injection maintenance dredging operations is

considered to be a localised temporary impact of moderate negative magnitude6.

6 When using the NRA EcIA criteria for assessing impact magnitude

NIS Appendix F F11

Figure 46: Peak sediment deposition depths in Sligo Harbour during water injection dredging operations

(also showing sensitive areas/monitoring stations – See 1.1.9)

NIS Appendix F F12

Figure 47: Final sediment deposition depths on completion of water injection dredging operations

(also showing sensitive areas/monitoring stations – see 1.1.9)

NIS Appendix F F13

11.1.8. Suspended Sediments, pH and Dissolved Oxygen

Dredging also has the potential to cause temporary increases to the amount of suspended

sediments held in the water column.

The hydrodynamic model was also used to predict the duration and extent of the changes to

suspended sediments within the sensitive environment of Sligo Harbour.

In accordance with the monitoring requirements of Council Directive 79/923/EEC, on the

quality required of shellfish waters, and Council Directive 91/492/EEC, which sets down the

health conditions for the production and placing on the market of live bivalve molluscs, the

Marine Institute collect water and shellfish samples from major shellfish growing areas at

regular intervals and analyses them for physicochemical parameters, trace metal levels and

chlorinated hydrocarbon concentrations. Sampling results were obtained from the Marine

Institute for the shellfish beds within Sligo Harbour for use as a baseline indicator of

suspended sediments.

Table 7 below shows suspended sediment concentration values measured in 2009 -2011 at

this water quality sampling location. The station is also shown as Station Mon-3 in Figure 49.

Table 7: Measured suspended sediment in Sligo Harbour by Probe By Lab

Date Actual Lat

Actual Long

Sample Depth

(m)

DOXY (%)

pH (sc)

PSAL (PSU)

TEMP (degC)

TURB (%)

CPHL ( g/l)

SUSP (mg/l)

COLOR (sc)

03/12/09 54.2893 -8.5238 0.5 99 8 16.19 8.2 25.6 18.6

16/12/09 54.2893 -8.5238 0.5 96.3 8.11 26.5 7.79

20/01/10 54.2893 -8.5238 0.5 109 8.23 13.03 7.05

16/02/10 54.2893 -8.5238 0.5 108 8.45 23.7 7.57 12 13.6

23/03/10 54.2893 -8.5238 0.5 103 8.32 31.69 9.7

14/04/10 54.2893 -8.5238 0.5 135 8.48 16.65 13.1

17/05/10 54.2893 -8.5238 0.5 124 8.31 31.85 13.7 <2 6.6

23/06/10 54.2892 -8.5287 0.5 140 8.68 28.12 18.1

13/07/10 54.2892 -8.5242 0.5 130 8.42 32.22 17.7

23/08/10 54.2898 -8.5252 0.5 102 8.34 28.46 17 72 7.9

20/09/10 54.2883 -8.5263 0.5 143 8.8 25.32 16.4

21/10/10 54.2893 -8.5232 0.5 114 8.11 30.11 13.2

13/06/11 54.2895 -8.5240 0.5 110 8.27 28.74 18.9 8 <4

11/07/11 54.2895 -8.5242 0.5 131 8.15 24.5 18.8 <2 30.2

14/12/11 54.2893 -8.5238 0.16 108 7.97 25.58 5.3 22.9 136

(Source: Marine Institute data request)

NIS Appendix F F14

It can be seen that measured values vary widely depending on the date when the

measurements were taken (from <2 to 72 mg/l). The sediments disturbed by the dredging

process in the navigation channel will cause temporary increases in suspended sediment

concentration within Sligo Harbour during dredging operations.

As stated above, actual dredging operations will only occur for around 4.5 hours per tide

(12.4 hours) and dredging should be substantially completed over a period of 5 tides. The

dredging should be timed to occur only during the early part of the ebbing tide, in order to

give the mobilised particles the greatest opportunity of being transported a sufficient distance

downstream.

The influence of the dredging may continue for several more days, as the sediments

removed from the site are brought into re-suspension during subsequent tides, therefore the

simulations were run for a total of 28 days.

The average value envelopes for the suspended sediment concentrations throughout the

dredging is presented below in Figure 48.

On this figure the green areas show mean suspended sediment concentrations of 80-

100mg/l, rising to 200-300mg/l in the yellow areas immediately surrounding the dredging

area during the water injection maintenance dredging campaign.

In practice however, dredging does not cause a continuous increase above background for

the duration of operations but rather causes the suspended sediment concentration to rise

rapidly shortly after active dredging begins during each tide, achieving a peak around the

period of slack water, before returning back to background or near-background values before

the next dredging session begins on the next tide. Following completion of dredging, the

displaced material lying on the seabed will be swept up into suspension during subsequent

tides as current speeds increase, settling out temporarily as speeds drop again during slack

water before being picked up again and moved on during the next tide.

NIS Appendix F F15

Figure 48: Mean suspended sediment concentrations during water injection dredging operations (for bottom 0.5m of water column)

(also showing sensitive areas/monitoring stations – see 1.1.9)

NIS Appendix F F16

11.1.9. Sensitive Areas During the ecological baseline studies (see Appendix D.1(viii)), four areas which have the

potential to be vulnerable to adverse impacts of the dredging activities were identified.

These areas are indicated on Figure 49.

Figure 49: Location of Identified Sensitive Areas and Timeseries Locations Google aerial photo dated 2006 © Google/Digitalglobe/NASA

Area 1: The area surrounding Cartron Marsh and Standalone Point, where dredging activity

has the potential to cause impacts on important bird feeding areas by affecting forage or prey

species.

Area 2: an environmentally important habitat of seagrass (Zostera) which may be vulnerable

to smothering caused by the dredging.

Area 3: encompassing the main area of commercial and natural shellfish beds, including the

large mussel bank in the centre of the harbour.

Area 4: a commercial clam production area

In order to portray in a more appropriate manner the magnitude and duration of the changes

to the suspended sediment concentrations within the harbour, a time series showing the

NIS Appendix F F17

peak concentration of suspended sediments in the bottom 0.5m of the water column during

and after dredging as well as sedimentation depths has been produced for 4 points:

Point Mon-1 (Cartron Marsh)

Point Mon-2 (Southern Cummeen Strand)

Point Mon-3 (Commercial mussel bed and Marine Institute baseline monitoring station)

Point Mon-4 (Commercial clam bed)

The results are presented only for the bottom 0.5m as it is changes to this part of the water

column that will have greatest impacts on the shellfish and intertidal/subtidal bird prey and

forage species which are present within the harbour.

Figure 50 to Figure 53 shows the time series of peak suspended sediments and peak

sedimentation for the duration of the proposed water injection dredging campaign at each of

the four stations within Sligo Harbour.

Figure 50: Time series showing peak Suspended Sediment Concentration in bottom 0.5m and Sedimentation for Carton Marsh Area during dredging campaign (Point Mon-1)

NIS Appendix F F18

It can be seen in Figure 50 that the area most affected, with the highest peak values of all of

the time series recorded is in Cartron Marsh, due to it being the closest station to the

dredging area. The red lines show the predicted peak suspended sediment concentrations

in the bottom 0.5m of the water column while the blue lines show the peak depth of sediment

settling out (depths in mm being approximately equivalent to the kg/m² divided by 1.65). It

can be seen that during dredging operations, which will occur for 3 days over the first spring

tide period in the model, the peak suspended sediment levels increase rapidly with

increasing current speed during each tide. The highest peaks, occurring on 3 of the spring

tides, reach levels of around 4-5g/l, but more typical peak values are below 1.5g/l.

The temporary rises in suspended sediment concentration typically last up to 3 hours, but

with the peak values (seen as “spikes” on Figure 11) lasting for a much shorter period of only

15-30 minutes. The period between peaks (tides), when concentrations return back to

baseline, or near baseline, levels will be much longer (around 9 hours). The short duration of

the peak concentrations is confirmed when we revisit the mean suspended sediment

concentration values for the time series (Figure 9) which shows a mean concentration of

60mg/l throughout the duration of the timeseries at Point Mon-1.

It can be seen from the blue lines in the Carton Marsh time series that when the current

speeds drop, the material settles out with the greatest peak sedimentation depth of around

13mm occurring during the tide immediately following the completion of the dredging

operations. After 5 days, the depth of sediment being settled out during the slack tide is in

the order of 2.5mm. It can be seen that during the neap tides the current speeds are not

sufficiently strong to pick up the deposited material during each tide and it remains in place

for several days, however during the next spring tide the stronger current speeds pick up

more sediment, causing a brief rise in both suspended sediments and subsequent

settlement, before the material is finally flushed out of the area at the end of the spring tide,

around 20 days after dredging operations began.

The effects of the water injection dredging at Cartron Marsh can therefore be predicted to be

moderate negative in magnitude but temporary in duration.

NIS Appendix F F19

Figure 51 : Time series showing peak Suspended Sediment Concentration in bottom 0.5m and Sedimentation for Southern part of Cummeen Strand during dredging campaign (Point Mon-2)

At Point 2, on the southern shore of Cummeen Strand, it can be seen that it takes until the

next spring tide before the sediment mobilised by the dredging reaches the site. Peak

suspended sediments at this site are modelled to reach around 600mg/l on the highest

spring tide following the dredging, with more typical peak values below 100mg/l. The

average suspended concentration at this point across the modelling period is less than

20mg/l. In between tides, sedimentation will be barely perceptible with levels of around

0.4mm occurring during slack tide. The impact arising from this small increase in suspended

sediment and sedimentation is predicted to be neutral and temporary.

NIS Appendix F F20

Figure 52 : Time series showing peak Suspended Sediment Concentration in bottom 0.5m and Sedimentation near commercial shellfish farm during dredging campaign (Point Mon-3)

At Point 3, which is located at the Marine Institute monitoring station close to the commercial

shellfish farm on Cummeen Strand, small peaks in suspended sediment (red lines) can be

seen during the spring tides. These peak increases will be in the order of 50-250mg/l with a

small number of tides where material in suspension will settle out temporarily in this site.

Average suspended sediment concentrations throughout the modelled period at this site are

below 20mg/l. The depths of sedimentation are not predicted to be significant, with temporary

sedimentation depths in the order of 0.4 to 0.8mm (blue line) predicted. The impact arising

from this small increase in suspended sediment and sedimentation at Point 3 is predicted to

be neutral and temporary.

NIS Appendix F F21

Figure 53: Time Series showing peak Suspended Sediment Concentration in bottom 0.5m and Sedimentation for commercial clam farm during dredging campaign (Point Mon-4)

At Point 4, the commercial clam farm to the west of Cummeen Strand, the effects of the

dredging will be barely perceptible. During the spring tide following the dredging, very small

peak suspended sediment concentrations of less than 60mg/ will be experienced at this site.

The predicted impact at this site is anticipated to be neutral and temporary.

11.1.10. Conclusion

It can be seen from the modelling results that significant elevations in suspended sediment

within Sligo Harbour caused by the dredging only occur in the immediate vicinity of where the

dredger is working, and within the confines of the navigation channel.

The areas in which sensitive habitats have been identified, at Cartron Marsh, southern

Cummeen Strand and at the nearby aquaculture sites will experience very short term

increases in suspended sediment concentrations in the lowest 0.5m of the water column and

small amounts of temporary sedimentation, particularly during the water injection dredging

phase. However, the majority of the dredged material will eventually settle out around the

NIS Appendix F F22

training walls or will be transported out of the harbour during the following spring tide where

the material will settle out on the sand banks at the entrance to Sligo Harbour and the

residual effects will not be significant.

The chemical analysis of the proposed material to be dredged has shown that it has a

relatively low organic content. The risk of the dredging causing significant impacts to

dissolved oxygen levels in the harbour is therefore considered to be low. Mitigation

measures including real time monitoring of suspended sediment levels and dissolved oxygen

levels are described in Attachment F.1.

NIS Appendix F F23

11.2. COMPUTATIONAL MODEL OF CONVENTIONAL DREDGING OPERATIONS (250,000m³)

11.2.1. Introduction Hydrodynamic modelling was undertaken as part of the study to investigate the impact of the

conventional dredging of c. 250,000m³ of sediments from the navigation channel on the

hydraulic regime of Sligo Harbour and on the sedimentation in the harbour area during the

dredging operations. The modelling was used to examine the effect of:

1. The change in channel bathymetry on the tidal flows and water levels, and 2. The dispersion and fate of material spilled during the period of the dredging

operations.

11.2.2. Computational Models

11.2.2.1. Modelling Software

The computational models used in this study were based on the MIKE 21 coastal process

software which has been developed by the Danish Hydraulics Institute. The modules of this

coastal process modelling system used in this study comprised:

2D hydrodynamic flow models Particle tracking models

Hydrodynamic Flow ModelThe main hydrodynamic flow model used in the study was a 2D MIKE21 nested HD flow

model consisting of a 30m grid outer model and a finer 10m grid inner model. The extent of

the nested flow model is shown in Figure 54 below.

NIS Appendix F F24

Figure 54: Extent of 30 and 10 metre grid nested flow model

Dredged Spoil Disposal ModelsThe dredged spoil disposal modelling was undertaken using the MIKE 321npa model. This is

a particle tracking model that uses the hydraulic flow regime from the MIKE21 nHD model to

simulate the transport and fate of material discharged to the water column. The model can

include variable graded material and takes effect of re-erosion of deposited sediment so it is

particularly suitable for the simulation of the disposal of dredged spoil.

11.2.2.2. Bathymetry

The bathymetry for the model studies was taken from very detailed LiDAR and multi-beam

hydrographic surveys of the entire model area undertaken by the Geological Survey of

Ireland in 2008 under the INFOMAR project. These surveys comprised some 46 Gigabytes

of xyz data.

11.2.2.3. Model Calibration

NIS Appendix F F25

The models were calibrated against flow measurements undertaken in December 2009 using

two ADCP current meters, one deployed to the west of Deadman's Point and the other in the

channel to Drumcliff Bay. The model and current meter velocities were compared for tidal

conditions with the same tidal range and the model results were found to be consistent with

the field measurements.

11.2.3. Model simulations

11.2.3.1. Tidal Flow Modelling

Model Tidal Flow RegimeThe tidal flow modelling was undertaken for a whole month of tides based on a typical period

31 January 2003 to 2 March 2003. The fresh water flow into Sligo harbour was set at 14.7

cumecs which was derived from the annual average flow for the catchments feeding into the

Garavogue River. The tidal curve at Oyster Island for the model period is shown in Figure 55.

Figure 55: Tidal curve for 1 month simulation period.

The tidal modelling was undertaken for the existing bathymetry and for the bathymetry with

the proposed dredged channel completed. Typical flow patterns are shown in Figure 56 and

NIS Appendix F F26

Figure 57; which illustrate mid flood and mid ebb tides respectively around Sligo harbour for

a spring tide.

Figure 56: Typical flow patterns in Sligo harbour - flood tide

Figure 57: Typical flow patterns in Sligo harbour - ebb tide

NIS Appendix F F27

Impact of Dredging on Tidal Flow RegimeThe impact of the proposed dredging of the channel to the deepwater quay was assessed in

terms of changes to overall tidal levels and tidal flow velocities.

Figure 58 – Figure 60 show a comparison of the tidal curves at Sligo town for the existing

situation (blue) and with the post-dredging channel in place (red). It can be seen in Figure 58

that during a neap tidal cycle there is an imperceptible difference in water levels between the

existing and post-dredging channels.

The overall average tidal curve shows a minor reduction in water level during low tide, but no

increase in water level at high tide. During an extreme spring tide, there is a slightly greater

reduction in the water level during low tide. The proposed dredging will not result in any

increase in water level at high tide, therefore the proposed dredging of the channel will not

cause any increase in the risk of flooding in Sligo from high spring tides.

The reduction in water level during an extreme low spring tide is caused by the removal of

the bar within the shipping channel by the proposed dredging. At present, this bar slows

down the passage of water exiting the channel at low tide, causing some water be retained

or pooled behind it. If the bar is dredged, the water will be able to drain more freely at low

tide, thus causing lower water levels and possible drying out of the channel upstream of the

bar at extreme low spring tides. As can be seen on Figure 60 this drying will last for a

maximum of 2 hours.

NIS Appendix F F28

Figure 58: Comparison of existing and dredged channel tidal curves at Sligo (neap tide)

Figure 20: Comparison of existing and dredged channel tidal curves at Sligo (overall average)

NIS Appendix F F29

Figure 60: Comparison of existing and dredged channel tidal curves at Sligo (extreme spring tide)

The impact of the proposed dredging on the flow regime in Sligo Harbour has been assessed

by comparing the mean and peak flow velocities for both flood and ebb tides. Different plots

have been used to highlight the magnitude and location of changes in the tidal current

velocities which are predicted to occur due to the proposed dredging of the channel into

Sligo's deep water quay. The analysis has been shown only for spring tides, as the

differences will be more pronounced during spring tides compared to the effect at neap tides.

Figure 22 and Figure 23 show the difference in the mean tidal velocity for both flood and ebb

spring tides. In these diagrams, the difference in the tidal velocity is calculated by comparing

the average tidal velocity over the flood or ebb period for the model with the dredged channel

in place and subtracting the equivalent flows for the model with the existing bathymetry. It will

be seen from these diagrams that the difference in the mean velocities is generally very

small (less than 0.1 m/s) and the changes are restricted to the area around the channel and

the northern section of the harbour area.

NIS Appendix F F30

Figure 22: Difference in mean spring flood tide velocity - proposed minus existing

Figure 23: Difference in mean spring ebb tide velocity - proposed minus existing

Figure 24 and Figure 25 show the difference in the peak tidal velocity for both flood and ebb

spring tides. The diagrams show the difference in the maximum tidal velocity that occurs at

any time during the period at every grid cell within the model area. It should be noted that

these peak velocities will not necessarily occur at the same time in each part of the harbour

area. In these diagrams the difference in the tidal velocity is calculated by taking the peak

tidal velocity during the flood or ebb period for the model with the dredged channel in place

and subtracting the equivalent flows for the model with the existing bathymetry.

NIS Appendix F F31

Figure 24: Difference in peak spring flood tide velocity - proposed minus existing

Figure 25: Difference in peak spring ebb tide velocity - proposed minus existing

As with the mean tidal flow difference plots, it can be seen that the impact of the dredging on

the peak tidal flow speeds is generally insignificant, except in the area of the channel itself

where increases of up to 0.4m/s may be experienced in localised areas. Peak speeds in the

area north of the navigation channel may be slightly decreased by around 0.1m/s.

In summary, the tidal flow modelling indicates that while the proposed dredging will lower the

level of the low water spring tides in the channel at Sligo, the high spring tide level will be

unaffected by the proposed dredging works. The dredging will have an insignificant effect on

NIS Appendix F F32

the current flows in the harbour area except in the area of the channel and adjoining northern

section of the harbour. The secondary main harbour drainage channel, to the south of middle

bank, experiences a drop in peak current speeds of up to 0.2 m/s whilst parts of the

navigation channel have increased speeds of up to +0.4 m/s in very localised areas with

more typical peak speed changes in the order of -0.05 to +0.05m/s.

11.2.3.2. Dredging Plume Simulation Modelling

Dredging ProgrammeThe dredged plume modelling simulations were undertaken to provide information on the

dispersion and fate of dredged material discharged to the water column during the dredging

of some 250,000 cubic metres of material required to deepen the approach channel.

The precise methodology for dredging will not be known until a dredging contractor has been

appointed, therefore a conservative approach has been taken to calculate the dredging

impacts, using the “worst case” impacts. The water depths in the existing channel are such

that it is likely that the dredger will have to dig its way upstream and that it will only be able to

dredge during the upper half of the tidal cycle. Thus for the modelling simulations it has been

assumed that the dredging programme will be organised to dredge during periods when the

water levels are above mid tide level and sail to and from the disposal area during the lower

half of the tidal cycle. For the purposes of the simulation it was assumed that it will take four

months to undertake the dredging work. This gives an average dredging quantity of about

2,100 m³ per day and an excavation rate of about 175 m³ per hour while the dredger is

working in the channel. These figures represent a “worst case” scenario using a stationary

dredger and more than one transportation barge to transport the dredged material to the

proposed dump site. In the event of the dredging operations using a mobile dredger or

single barge, the dredging will take place over a longer period of time with lesser quantities of

suspended sediments being released and the impacts on the environment will be reduced.

Flow Model DataThe dredging plume modelling was undertaken using the M321 npa particle tracking model

which simulates the transport and deposition of material discharged into the water column.

The model uses the data from the tidal model simulation as the basic hydrodynamic input to

the simulations.

The tidal models for both the existing channel and with the proposed dredged channel in

place were used for the dredging simulation modelling. The hydrodynamics with the existing

NIS Appendix F F33

channel were used for the dredging of lower section of the channel, i.e. seaward of the end

of the rebuilt training wall, while the hydrodynamics with the proposed deepened channel in

place were used for the simulations of the dredging of the upper channel section up to the

deep water quay. The 30 day tidal curve used in the simulations is shown in Figure 26.

Figure 26: Tidal curve for hydrodynamic regime used in the dredging simulations

NIS Appendix F F34

Bed sediments and dredging lossesAs noted in Attachment D.1 and Appendix D.1(iv), a number of bed samples were analysed

as part of the study. The information from the various samples shows consistently that the

material to be dredged is predominantly a fine grey silty sand. Even though there is an

increase in the shell and gravel fraction further downstream in the channel, only the finer

fractions are suspended into the water column during dredging, with the heavier fractions

settling out within a few metres of the dredger.

The losses from the dredger have been assessed using on on-site measurements made

during the construction of the Denmark – Sweden fixed link tunnel and bridge and by

reference to data contained in “Scoping the Assessment of Sediment Plumes from Dredging”

CIRIA 547. As the exact type of dredger which will undertake the work is unknown at this

stage, a conservative approach to the losses of material to the water column was taken.

Thus the total losses to the water column were assumed to be 3% of the dredged volume

represented by a 2% source at 2.5 metre below the surface and a 1% source at the surface.

The Mike 321 npa model simulates the fate of the loss of material from the dredgers by

releasing particles into the water column and tracking each particle throughout the simulation

process. A range of grain sizes have been used in the model, in order to cater for the

sediment grading of the dredged material. The grading used for the main source located at

2.5 metres below the surface was based on the grading in the PSA results from the bed

material samples. This source had the distribution of grain size shown below.

The source at the surface had a finer grading, as the losses at the surface come from

overspill or washout of finer fractions of the dredged material. The grading of the source at

the surface used in the study was as follows:


0.375 6

0.187 62

0.090 20

0.050 7

0.030 5

NIS Appendix F F35


0.090 45

0.050 30

0.030 25

Dredging SimulationsThe dredging programme and tidal conditions were as noted in Sections 0 and 0 above. The

dredging of the channel was considered in two halves, i.e. a lower section comprising the

channel up to the commencement of the rebuilt training wall on the western side of the

channel and an upper section consisting of the section of the channel beside the rebuilt

training wall, up to the deep water berth. Each section of the channel was assumed to take 2

months to dredge giving a total of 4 months dredging. This is the worst case scenario,

assuming the dredging would be done as quickly as possible. In reality the dredging could

take longer in which case the scale of the impact on the harbour will be reduced.

In the simulations the dredger was assumed to work its way up the channel from seaward

dredging half the channel width at a time. The sources in the model were moved to keep

track of the dredger with breaks in the sequence while the dredger was travelling to and from

the dump site.

The simulations for the lower and upper channel sections were each run for the 30 day tidal

sequence and then results for each area multiplied up by two to match the appropriate

dredging period. Finally, the results of the dredging of the two channel sections were

combined to give the overall deposition from the whole of the dredging operation.

Results of the Dredging SimulationsThe results of the dredging simulations are shown graphically by a series of model output

diagrams. The figures show the sediment deposition depths at the completion of the

dredging as well as the average value envelopes for the suspended sediment concentrations

throughout the dredging of each of the channel sections. The maximum sediment deposition

depth envelopes are also shown for the deposition of sediment during the dredging of each

of the channel sections.

The maximum deposition envelope diagrams represent the maximum value that occurred at

each grid point in the model at any time during the simulation period, even if the period of the

peak value is very short. The average concentration envelope is the average value at each

NIS Appendix F F36

grid cell in the model throughout the period when the cell is wet. In these diagrams the period

when the cell dries out (e.g. at low tide) is ignored when calculating the average.

Figure 27 - Figure 29 show the peak sedimentation depth during the dredging of the lower

and upper channel sections and on final completion of dredging operations. It will be seen

from these diagrams that sediment is temporarily deposited in a small number of sheltered

areas, mainly along the sides of the channel and along the north shore of the harbour area,

during dredging. Outside of these sites the deposition depth is low. It should be noted that

these peak values are typically of a short duration and tend to occur during the turn of the

tide. The material may then be re-suspended as the tidal currents pick up during the next

tidal cycle. If unacceptable localised deposits remain at the end of the dredging process,

these may be cleaned up and reinstated after dredging operations are completed.

Figure 27: Peak sediment deposition depths during dredging of lower channel

NIS Appendix F F37

Figure 28: Peak sediment deposition depths during dredging of upper channel

NIS Appendix F F38

The pattern of residual sediment deposition following the completion of the dredging is

shown in Figure 29. It will be seen that significant deposition only occurs in a small number of

sheltered areas along the coastline, particularly in the lee of the training wall and along small

parts of the north shoreline.

Figure 29: Sediment deposition depths on completion of all dredging operations

The maximum peak sedimentation during dredging in the affected areas is between 20 and

70mm (see Figure 27 & Figure 28). As described above much of this deposition is

temporary, occurring only for a very short period of time during slack tide and much of the

material will be re-suspended when current speeds pick up during the following tide.

This resuspension will significantly decrease the final residual amount of deposited sediment

(Figure 29), which is therefore lower than the “during dredging” peak values within these

localised areas.

The maximum deposition depth of dredged sediments in Sligo Harbour on completion of

dredging is less than 1mm in the majority of the harbour area. The deposition exceeds

25mm only in a small number of very localised sites, which are mainly around the training

wall and northern shore of the harbour. Outside of this area, two very small sites (less than

300m²) will experience final sediment deposition depths in excess of 25mm adjacent to

Coney Island and at the southern shore of Cummeen Strand.

NIS Appendix F F39

The combined area of the intertidal sites where deposition depths in excess of 25mm will

occur is 3.5ha. This represents 0.07% of the overall SAC area (c.4854ha).

Overall the amount of sediment deposition in the harbour area on completion of dredging is

considered to be insignificant.

NIS Appendix F F40

11.2.4. Impacts of Dredging on Sensitive Habitats

During the intertidal/subtidal and birds baseline studies, three areas which have the potential

to be vulnerable to adverse impacts of the dredging activities were identified.

These areas are outlined on Figure 30, which also shows the mean suspended sediment

concentration in lower 0.5m of water column during dredging of the lower section of the

channel.

Area 1: The area surrounding Cartron Marsh and Standalone Point, where dredging activity

has the potential to cause impacts on important bird feeding areas. The mean suspended

sediment concentration at this location arising from the dredging operations in the lower part

of the channel is shown in more detail on Figure 31 and the upper part of the channel in

Figure 35.

Area 2: an environmentally important habitat of seagrass (Zostera) which may be vulnerable

to smothering caused by the dredging. The mean suspended sediment concentration at this

location arising from the dredging operations in the lower part of the channel for this area are

shown in detail on Figure 32 and for operations in the upper channel in Figure 36.

Area 3: encompassing the main area of commercial and natural shellfish beds, including the

large mussel bank in the centre of the harbour. The mean suspended sediment

concentration at this location arising from the dredging operations in the lower part of the

channel is shown in more detail in Figure 33 and for operations in the upper channel in

Figure 37.

In all cases the suspended sediment concentration within the bottom 0.5m of the water

column has been plotted as it is changes to this part of the water column that will have

greatest impacts on the shellfish and intertidal/subtidal bird prey and foraging species which

are present within the harbour.

NIS Appendix F F41

Figure 30: Mean suspended sediment concentration in lower 0.5m of water column during conventional dredging of the lower section of the channel

(showing location of potentially vulnerable areas and monitoring stations)

Figure 31: Lower channel conventional dredging - mean suspended sediment concentration in Area 1 – Cartron/Standalone Point

NIS Appendix F F42

Figure 32: Lower channel conventional dredging - mean suspended sediment concentration in Area 2 – seagrass habitat in southern part of Cummeen Strand

Figure 33: Lower channel conventional dredging - mean suspended sediment concentration in Area 3 – commercial and natural shellfish beds

The average level of suspended sediment in the bottom 0.5m of the water column during the

conventional dredging operations in the upper section of the channel is shown in Figure 34

and in more detail on Figure 35 - Figure 37.

NIS Appendix F F43

Figure 34: Mean suspended sediment concentration in lower 0.5m of water column during conventional dredging of the upper section of the channel

(showing location of potentially vulnerable areas and monitoring stations)

Figure 35: Upper channel conventional dredging - mean suspended sediment concentration in Area 1 –Cartron Marsh/Standalone Point

NIS Appendix F F44

Figure 36: Upper channel conventional dredging - mean suspended sediment concentration in Area 2 – Seagrass habitat in southern part of Cummeen Strand

Figure 37: Upper channel conventional dredging - mean suspended sediment concentration in Area 3 – commercial and natural shellfish beds

The concentrations shown in Figure 30 - Figure 37 are above background values and are the

average over the time when the particular part of the area is wet during the period of time

that particular section of the channel is being dredged.

NIS Appendix F F45

Overall the impact of the dredging is expected to be relatively small, as both the deposition

depths and the increase in the level of the suspended sediment concentrations in the greater

part of the harbour area are not particularly significant.

In accordance with the monitoring requirements of Council Directive 79/923/EEC, on the

quality required of shellfish waters, and Council Directive 91/492/EEC, which sets down the

health conditions for the production and placing on the market of live bivalve molluscs, the

Marine Institute collect water and shellfish samples from major shellfish growing areas at

regular intervals and analyses them for physicochemical parameters, trace metal levels and

chlorinated hydrocarbon concentrations. Sampling results were obtained from the Marine

Institute for the shellfish beds within Sligo Harbour for use as a baseline indicator of

suspended sediments.

Table 8 below shows suspended sediment concentration values measured in 2009 to 2012

at the same sample location.

NIS Appendix F F46

Table 8: Water Quality Measurements in Sligo Harbour

by Probe Lab Analysis

Date (yymmdd) Fixed Lat

Fixed Long

Sample Depth (m)

DOXY (%) PH (sc)

PSAL (PSU)

TEMP (degC)

TURB (%)

CPHL (ug/l)

AG (ug/l)

AS (ug/l)

CD (ug/l)

CR(ug/l)

CU (ug/l)

NI (ug/l)

PB (ug/l)

ZN (ug/l)

SUSP (mg/l)

COLOR (sc)

091203 54.2893 -8.5238 0.5 99 8 16.19 8.2 25.6 18.6

091216 54.2893 -8.5238 0.5 96.3 8.11 26.5 7.79

100120 54.2893 -8.5238 0.5 109 8.23 13.03 7.05

100216 54.2893 -8.5238 0.5 108 8.45 23.7 7.57 12 13.6

100323 54.2893 -8.5238 0.5 103 8.32 31.69 9.7

100414 54.2893 -8.5238 0.5 135 8.48 16.65 13.1

100517 54.2893 -8.5238 0.5 124 8.31 31.85 13.7 <2 6.6

100623 54.2893 -8.5238 0.5 140 8.68 28.12 18.1

100713 54.2893 -8.5238 0.5 130 8.42 32.22 17.7

100823 54.2893 -8.5238 0.5 102 8.34 28.46 17 72 7.9

100920 54.2893 -8.5238 0.5 143 8.8 25.32 16.4

101021 54.2893 -8.5238 0.5 114 8.11 30.11 13.2

110613 54.2893 -8.5238 0.5 110 8.27 28.74 18.9 8 <4

110711 54.2893 -8.5238 0.5 131 8.15 24.5 18.8 <2 30.2

111214 54.2893 -8.5238 0.16 108 7.97 25.58 5.3 22.9 136

111214 54.2893 -8.5238 0.5 - - - - - - <1 <1 <0.04 <0.5 0.7 0.47 0.19 2.88 - -

120423 54.2893 -8.5238 0.5 - - - - - - - - - - - - - - <5 11.8

120423 54.2893 -8.5238 1.72 105 7.99 30.17 11.2 - 0.49 - - - - - - - - - -

120521 54.2893 -8.5238 1.35 122 8.22 30.76 16.74 9.7 5.83 - - - - - - - - - -

Source: Marine Institute Data Request

NIS Appendix F F47

Figure 38 shows the locations of 4 model points which have been chosen as they

represent potentially vulnerable areas. These stations are also replicated as

suggested monitoring points Mon-1 to Mon-4. Month-long time series of the

suspended sediment concentration at these stations have been extracted from the

model and are presented in Figure 39 - Figure 42. Point 3 (Mon-3) marked on this

figure represents the location of the measured baseline values shown in Table 8.

Figure 38: Mean suspended sediment concentration in bottom 0.5m during conventional dredging at location of 4 points in potential vulnerable areas

It can be seen that measured values vary widely depending on the date when the

measurements were taken (from <2 to 72 mg/l). The sediments disturbed by the

dredging process in the navigation channel will cause temporary increases in

suspended sediment concentration within Sligo Harbour during dredging. Figures

Figure 39 to Figure 42 show a time series of the modelled peak suspended sediment

concentrations spanning a typical month at each of the four “vulnerable area” points.

NIS Appendix F F48

Figure 39: Time series showing Suspended Sediment Concentration in Cartron Marsh Area during conventional dredging (Point 1)

Figure 40: Time series showing Suspended Sediment Concentration in Southern part of Cummeen Strand during conventional dredging (Point 2)

Figure 41: Time series showing Suspended Sediment Concentration near commercial shellfish farm during conventional dredging (Point 3)

NIS Appendix F F49

Figure 42: Time Series showing Suspended Sediment Concentration near commercial clam farm during conventional dredging (Point 4)

It can be seen that when dredging operations occur during spring tides, the

suspended sediment concentration at each of the four sites shown in Figure 39 -

Figure 42 rises quickly (around the period of slack water during each tide) but it also

quickly returns back to the background values.

During spring tides, the suspended sediment concentrations reach relatively high

peak values during each tide (when compared to the measured background in Table

8), however the actual duration of each “spike” is very short (as dredging only occurs

for a short period each tide). The concentration peaks, or “spikes” at any given point

will typically last up to two hours, but with the highest values lasting for a period of

only 15-30 minutes. The period between peaks (tides), when concentrations return

back to baseline levels, will be much longer (around 10 hours).

As can be seen on Figure 39 to Figure 42, during the neap tides suspended

sediment concentration levels at each of the four sites remain at background levels

during dredging operations.

In summary, the modelling shows that significant elevations in suspended sediment

within Sligo Harbour caused by the dredging only occur in the immediate vicinity of

where the dredger is working, within the confines of the navigation channel during

periods of spring tides.

The areas in which sensitive habitats have been identified, at Cartron Marsh,

southern Cummeen Strand and at the various aquaculture sites will experience very

short term increases in suspended sediment concentrations in the lowest 0.5m of the

water column, mainly during slack water at spring tides. As described in the Natura

NIS Appendix F F50

Impact Statement (Appendix D.1.(viii)) these increases are of short term duration

and are well within the tolerance levels of the sensitive flora and fauna within the

harbour, they are not considered to be significant

NIS Appendix G G1

APPENDIX G – LAMPREY, EEL AND SALMON DESKTOP REVIEW

SALMONID MIGRATIONS

Life Cycle Atlantic salmon Salmo salar and sea trout Salmo trutta (Plate G1 and G2) both have

marine and freshwater phases of the life cycle. Adult fish spawn in freshwater rivers

where their young develop for 1-3 years before migrating to richer feeding grounds at

sea. The maturing adult fish return to freshwater to breed after 1-2 years at sea.

Migrations to and from local rivers will require these fish to pass through the dredging

area in Sligo Harbour.

Plate G1 Atlantic salmon

Plate G2 Sea trout

NIS Appendix G G2

Salmon Conservation

The Atlantic salmon is listed in Annex II of the EU Habitats Directive (92/43/EEC) as

a species of European importance. EU member states are required to designate and

manage sites for listed species or habitats as a part of wider measures to ensure the

conservation of the habitats and species.

For several years fisheries scientists have been concerned about the declining

numbers of salmon returning to the Irish Coast due to a persistent phase of low

marine survival. Since 1996 a progressive series of conservation initiatives have

been introduced to address this decline in stocks culminating in the closure of mixed

stock coastal fisheries in 2007. Salmon stocks in Ireland are now managed on an

individual river basis with the objective that each river must exceed its Conservation

Limit for there to be any exploitation of fish to be permitted either by nets or rods.

The Scientific Sub-Committee of the National Salmon Commission provides annual

advice on harvest options for individual rivers in order to ensure that there are

sufficient spawning salmon remaining in each system to meet the required

conservation limit. The leading salmon rivers in the Sligo fisheries district are

currently open for salmon angling, although the Garravogue is subject to specific

restrictions due to a restricted quota.

Local salmon/sea trout rivers

There are a number of rivers discharging to Sligo Bay via Drumcliff Bay, Sligo

Harbour and Ballysodare Bay, all of which support one or both of the migratory

salmonids species, Atlantic salmon Salmo salar and sea trout Salmo trutta. The

principal rivers in this regard are the Ballysodare, the Garravogue and the Drumcliff

(Figure G1). Annual salmon catches in each of these river systems is shown inFigue

G2. There is currently no commercial netting for salmon in the estuaries of these

rivers.

NIS Appendix G G3

Figure G1 Map of region showing principal salmonid rivers draining to Sligo Bay

FigureG2 Annual salmon catch from principal local rivers, 2001-10 (Source: IFI)

0

500

1,000

1,500

2,000

20 01 20 02 20 03 20 04 20 05 20 06 20 07 20 08 20 09 20 10

Adj

uste

d to

tal s

alm

on c

atch

Ballisodare

Garravogue

Drumcliff

NIS Appendix G G4

Ballysodare River

This is one of the leading and most productive salmon rivers in Ireland. Due to

extensive conservation measures by the Ballysodare Fishing Club and IFI in recent

years, there is now a substantial run of spring salmon in the river from April to mid

June. This is followed by a large grilse run which peaks in June – July. There is some

substantial run of sea trout into the estuary on rising tides.

Garravogue River, Lough Gill and Bonet River system

The Garavogue is only just over 4 km in length from Lough Gill to the tidal reach. It is

predominantly fished on the east side of Sligo town close to where it flows out of. The

river gets a run of spring fish early in the year and later a larger run of grilse. There

are a series of angling clubs and privately owned fisheries throughout the system.

Drumcliff River and Glencar Lake

This system has a good stock of sea trout and also a modest run of salmon, both

early spring fish and summer grilse.

RECREATIONAL SEA ANGLING

Shore Angling

There are strong currents in the navigation channel in Sligo Harbour but there good

fishing is available in the channel from the north side between Rosses Point and

Deadman’s Point for sea trout, mackerel, bass, dogfish, bull huss, ray and tope. The

channel can also be accessed from the south side via Coney Island. The beach on

the west side of Coney Island is also noted for bass, flounder and occasional ray.

Boat Angling

Two charter boats based in Rosses Point and operate specifically in Sligo Bay and

provide reef fishing and general inshore angling for tope, ray, spurdog, dogfish and

occasional large skate. A number of boats based in Mullaghmore offer fishing in the

wider Donegal Bay area.

The Turbot Bank to the north west of the mouth of Ballysadare Bay is a recognised

area for turbot, thornback ray and blonde ray. Another reef is ‘the Ledge’ which lies

about 6.44km west of Coney Island with excellent pollack fishing. Ling, conger, tope

NIS Appendix G G5

and bull huss may also been taken in the vicinity while the area south of ‘Wheat

Rock’ produces common skate to more than 150lbs (68kg).

Sligo Bay also provides good fishing opportunities locally for small boat angling and

as this niche of saltwater angling increases in popularity so the fishing on Sligo Bay

will be opened up to a wider public.

EEL & LAMPREY MIGRATIONS

Eel (Anguilla anguilla)

Eels have a catadromous life cycle - young eels (elvers) migrate from the sea into

freshwater to feed and the resultant adults later return to sea to spawn. Juvenile eels

are likely to be present in the local estuaries in the Sligo area during March and April.

They are then believed to spend 10-15 years in freshwater systems before beginning

their return migration to sea during the autumn period as silver eels. Silvers are

therefore likely to be moving out through local estuaries during late autumn and early

winter.

Eels have been fished commercially in the Ballysadare and Garravogue systems.

However a long term and widespread decline in European eel stocks has been a

matter of concern for some time leading to EC European Eel Regulation (EC) No

1100/2007 in 2007. This Regulation aims to establish measures for the recovery of

the European eel stock in the form of Eel Management Plans for each eel river basin

including Western River Basin District which includes all catchments draining to Sligo

Bay. This will require Member States to reduce exploitation on all major eel river

basins and must demonstrate that at least 40% of the biomass of adult eels are

escaping to sea to spawn.

Lamprey

There are two migratory species of lamprey with marine phase in their life cycle, Sea

lamprey (Petromyzon marinus) and River lamprey (Lampetra fluviatilis) – both are

listed in Annexe 2 of the EC Habitat Directive. Adult sea lamprey enter the estuaries

of rivers from April onwards, and migrate some distance upstream to spawn which

usually takes place in late May or June.

NIS Appendix G G6

The juvenile larval phase is variable but averages about five years with subsequent

metamorphosis to the adult form takes between July and September. The timing of

the main migration downstream also varies and relatively little is known about the

adults after they reach the sea, where they have been found in both shallow coastal

and deep offshore waters.

The life cycle of the River lamprey is very similar to that of the sea lamprey. Mature

adults, having spent one to two years mainly in estuaries, stop feeding in the autumn

and move upstream into medium to large rivers, usually migrating into fresh water

from October to December.

Spawning takes place during March and April. The juveniles live and feed within silty

river substrates for up to 5 or 6 years before metamorphosing into fully formed adults

and then migrating downstream to estuaries or the open sea for the adult feeding

cycle.

The presence of eel and lamprey including (migratory phases) in local estuaries is summarised in Table G1

Month Eel Sea lamprey River Lamprey

Jan Adults present in estuary

Feb Adults present in estuary

Mar Elvers moving in through estuary Adults present in estuary

Apr Elvers moving in through estuary

Adults moving upstream Adults present in estuary

May Adults moving upstream Adults present in estuary

Jun Adults present in estuary

Jul Silvers moving out through estuary

Young moving downstream Adults present in estuary

Aug Silvers moving out through estuary


Sep Silvers moving out through estuary


Oct Adults present in estuary / Adults moving upstream

Nov Adults present in estuary / Adults moving upstream

Dec Adults present in estuary / Adults moving upstream

Table G1 Summary of migrations/presence of eel and lamprey in local estuaries at different times of year

The Proposed Dredging of the Navigation Channel …...The Proposed Dredging of the Navigation Channel at Sligo Harbour Vol. 3: Natura Impact Statement, to inform Appropriate Assessment

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