Bergen Covers/inside pages - NASCO · NINA SPECIAL REPORT 34 Norwegian Institute for Nature Research (NINA) Conveners’ Report Lars Petter Hansen Malcolm Windsor Hansen, L.P. & Windsor,

ICESCIEM

NINA SPECIAL REPORT 34

Conveners’ ReportLars Petter HansenMalcolm Windsor

Interactions Between Aquacultureand Wild Stocks of Atlantic Salmon

and Other Diadromous Fish Species:Science and Management,Challenges and Solutions

AcknowledgementsThe Symposium organizers would like to gratefully acknowledge the support of the

following Organizations:

Research Council of Norway Directorate of Nature Management (Norway)

Directorate of Fisheries (Norway)

Royal Norwegian Ministry of Fisheriesand Coastal Affairs

Norwegian Institute for Nature Research

Scottish Executive

Royal Norwegian Ministry of the Environment

DEFRA (UK)

Fisheries and Aquaculture Research Fund (Norway)

National Marine Fisheries Service (USA)

Directorate of Freshwater Fisheries and SalmonidEnhancement Fund (Iceland)

The Worshipful Company of Fishmongers (UK)

Atlantic Salmon Trust (UK)

Marine Institute (Ireland)

Intervet International BV (Netherlands)

Pharmaq AS (Norway)

ScanVacc AS (Norway)

Norwegian Farmers Union

Norwegian Salmon Rivers

City of Bergen

NINA SPECIAL REPORT 34Norwegian Institute for Nature Research (NINA)

Conveners’ ReportLars Petter HansenMalcolm Windsor

Hansen, L.P. & Windsor, M. 2006. Interactions between aquaculture and wild stocks of Atlantic salmon and otherdiadromous fish species: science and management, challenges and solutions. – NINA Special Report 34. 74 pp.Trondheim, October, 2006.

ISSN: 0804-412X

ISBN 10: 82-426-1736-8

ISBN 13: 978-82-426-1736-1

Copyright © Norwegian Institute for Nature ResearchThe publication may be freely cited where the source is acknowledged

Availability: Open. Publication type: Printed publicationCover picture Courtesy of the Scottish Salmon Producers’ Organisation, Perth, UK

Key words: Atlantic salmon, aquaculture, interactions, diadromous fish

Requests for copies of this report should be addressed to NASCO. Any enquiries about this report should be addressed to the Co-Conveners Dr Lars Petter Hansen ([email protected]) or Dr Malcolm Windsor ([email protected]).

NINA NASCO ICESNO-7485 Trondheim 11 Rutland Square H.C. Andersens Boulevard 44-46NORWAY Edinburgh EH1 2AS DK-1553 Copenhagen VPhone: +47 7380 1400 UNITED KINGDOM DENMARK Fax: +47 7380 1401 Phone: +44 131 228 2551 Phone: +45 33 38 6700http://www.nina.no Fax: +44 131 228 4384 Fax: +45 33 93 4215

http://www.nasco.int http://www.ices.dk

Interactions Between Aquacultureand Wild Stocks of Atlantic Salmon

and Other Diadromous Fish Species:Science and Management,Challenges and Solutions



C O N T E N T SPage

Preface (i)Executive Summary (ii)

1. Introduction 1

1.1 Background 2

1.2 Objectives of the Symposium 3

1.3 Structure of the Symposium 3

1.4 Acknowledgements 3

2. Overview of the Meeting 5

2.1 Session 1: Opening Addresses and Keynote Presentations 6

2.2 Session 2: Genetic and Ecological Interactions and their Management 7

2.3 Session 3: Disease and Parasite Interactions and their Management 10

2.4 Session 4: Poster Session 12

2.5 Session 5: Synthesis Session - Challenges and Solutions 14

3. Conclusions by the Conveners 17

3.1 Introduction 18

3.2 The Salmon Farming Industry 18

3.3 Disease and Parasite Interactions and their Management 19

3.4 Genetic and Ecological Interactions and their Management 19

3.5 Research Recommendations 21

3.6 Final Thoughts 21

4. References 23

Annexes

Annex 1 Abstracts 25

Annex 2 Keynote Presentations - Session Chairmen’s Summary 45

Annex 3 Genetic and Ecological Interactions and their Management - Session 49Chairmen’s Summary

Annex 4 Disease and Parasite Interactions and their Management - Session 55Chairmen’s Summary

Annex 5 Poster Session - Session Chairmen’s Summary 59

Annex 6 Take-Home Messages 63

Annex 7 List of Participants 71


(i)

Preface by the Presidents of NASCO and ICES

The subject of this Symposium is of vital importance notonly to those who are involved with conservation andmanagement of wild salmon stocks, but also to thoseinvolved in salmon farming. It is also a fine example ofscientists making their research relevant and responsive tothe needs of policy makers. As Presidents of NASCO andICES, we commend this report to you, and we reaffirmthe commitment of our Organizations to cooperate ontopics of mutual interest, like this one.

The two Conveners have done an excellent job indrawing together dozens of papers and presentations,hours of discussion and summaries by Chairmen andother participants. They have used all this information todraw conclusions that all of us should consider verycarefully. It is clear that while considerable progress isbeing made in improving understanding of interactionsbetween wild and cultured salmon and managing them,two significant challenges remain. These are to improvecontainment of farmed salmon either through physical orbiological means, and to control sea lice on farms, so thatdamage to the wild stocks is avoided. The stakes are high.For example, if the fears about genetic impacts ofescapees come true, and there is evidence that they arehappening, then we run the risk of compromising veryancient and diverse stock structures. This will harm boththe wild fish and the fish farming industry. We urge allthose concerned to read this report, and to actappropriately. We believe that there is now a basis forimproved cooperation between wild and farmed salmoninterests that should give confidence that solutions can befound to the remaining challenges in managing interactionsbetween cultured and wild salmon. These solutions arerequired urgently.

Ken Whelan, President of NASCO and Michael Sissenwine,President of ICES

Since the early 1980s, farming of Atlantic salmon hasbecome a major industry with a production in the NorthAtlantic in 2005 of approximately 0.8 million tonnes, or380 times the reported catch of wild salmon in the samearea. There are concerns about the disease, parasite,genetic and ecological interactions of salmon farming onthe wild salmon stocks and a regime is required thatallows the industry to prosper while safeguarding the wildstocks. Interactions between wild and cultured salmon arenot restricted to those arising from salmon farming.Where fish are deliberately released to the wild, a regimeis also required under which the risks as well as thebenefits are carefully considered.

In response to concerns about interactions betweensalmon aquaculture and the wild salmon stocks, a series ofinternational meetings has been convened over the last 16years to review scientific understanding of interactions andprovide guidance on appropriate management responses.The most recent of these symposia, held in Bergen,Norway, during 18 - 21 October 2005, is reported here.It is clear that since the first symposium in 1990 scientificunderstanding of the interactions between cultured andwild salmon has increased considerably. The latestinformation presented in Bergen confirms that culturedsalmon can have significant negative impacts on the wildstocks. While real progress has been made in managingthese interactions, some very significant challenges remain,particularly with regard to further reducing the impacts ofescapees and sea lice. A further major development sincethe last symposium in 1997 is that the representatives ofthe industry present in Bergen accepted that theirindustry can have damaging impacts on the wild stocks.This is very welcome because it is a prerequisite tocooperative action, which has developed considerablybetween wild and farmed salmon interests but whichneeds to continue and be enhanced if solutions are to befound to the remaining challenges.

The Conveners propose that interactions between farmedand wild salmon need to be virtually eliminated, not justreduced. There are risks not only from farmed salmon butalso from inappropriate stocking practices to beaddressed. While progress is being made in managinginteractions, the large scale of the salmon farming industrymeans that solutions are urgently required. We believethat progress in addressing the sea lice problem has beenmade and can continue to be made by concerted actionand widespread use of best practice but it is clear thatdifficulties remain, particularly with regard to protectingwild sea trout populations. The prospect of resistance

developing to the available lice treatments is a realconcern for both wild and farmed salmon interests.Progress has also been made in reducing escapees buttheir numbers remain large relative to the wild stocks andthey may be irreversibly damaging the stock structure anddiversity of the wild Atlantic salmon. In our view, thissymposium confirms that containment of farmed salmonmust be made much more effective. If physicalcontainment cannot be achieved then the use of sterilesalmon may be necessary.

We believe that if no action is taken now, and if the viewsof the many scientists and experts at the symposium, andthe two preceding symposia, are correct, we risk the lossof the diversity of local adaptations in the wild stocks ofsalmon in the North Atlantic. This may well have seriousconsequences for their fitness, productivity and ability tosurvive environmental change.

Lars Petter Hansen (ICES Co-Convener) and

Malcolm Windsor (NASCO Co-Convener)

6 October, 2006

Executive Summary


(ii)


(iii)

Sammendrag

Fra tidlig på 1980 tallet til i dag har oppdrett av Atlantisklaks utviklet seg til en betydelig industri. I 2005 ble detprodusert ca 0,8 mill tonn laks i Nord Atlanteren, eller ca380 ganger så mye som rapportert fangst av villaks i detsamme området. Effekter av lakseoppdrettet på villaks,som sykdommer, parasitter, genetikk og økologi erbekymringsfullt, og det er behov for å utvikle en strategifor å sikre de ville laksebestandene samtidig somlakseoppdrettet fortsatt forblir en viktig næring.Interaksjonene mellom vill og kultivert laks er dessutenikke bare begrenset til oppdrettet. En strategi hvor båderisikoer og fordeler blir nøye vurdert, er påkrevet også forlaks som skal settes ut i naturen for kultivering/havbeite.

Over de siste 16 årene har det blitt arrangert flereinternasjonale møter hvor både vitenskapelig forståelse ogrådgiving til forvaltningen om interaksjonene mellomlakseoppdrett og vill laks har vært tema. Det siste av dissesymposiene som ble holdt i Bergen 18 - 21 oktober 2005rapporteres her. Siden det første symposiet i 1990 har detvitenskapelige grunnlaget for å forstå interaksjonenemellom oppdrettet og vill laks økt betydelig. Informasjonensom ble presentert i Bergen bekreftet at oppdrettslaks kanha negativ effekt på ville laksebestander. Selv om det harvært framgang i forvaltningen av disse, gjenstår detbetydelige utfordringer, spesielt for å reduserelakselusproblemet. En viktig utvikling siden det sistesymposiet i 1997 var at representantene fra industriensom var tilstede i Bergen nå aksepterte at industrien kanha ødeleggende effekt på ville bestander. Dette er viktigfordi det er en forutsetning for samarbeid, og selv omdette nå har bedret seg betydelig må samarbeidetfortsette og bli ytterligere forbedret hvis man skal finneløsninger på utfordringene.

Vi foreslår at interaksjonene mellom opprettslaks og villaksmå praktisk talt elimineres, ikke bare reduseres. Problemerogså i forbindelse med feilaktig utsetting av laks forkultivering og havbeite må det også fokuseres på. Selv omdet er framgang i å forvalte interaksjonene krever detbetydelige volumet i oppdrettsvirksomheten hurtigeløsninger.Vi tror at framgangen som har kommet iforvaltningen av lakseluseproblemet kan videreføres ifelleskap og sørge for at kunnskapen om de besteløsningene blir spredt, men det er også klart at det erstore problemer som må løses, spesielt for å beskyttebestandene av sjøørret. Resistensutvikling mot deforskjellige avlusingsmedikamenter er også bekymringsfullbåde for oppdretts- og villaksinteressene. Det er ogsågjort framskritt i å redusere rømmingene fraoppdrettsanlegg, men det er fremdeles svært mange

oppdrettslaks som rømmer i forhold til størrelse påbestandene av villaks. Disse rømlingene kan medføreirreversible forandringer i bestandsstruktur og diversitet avvill laks.Vi mener at dette symposiet bekreftet at tiltak forå hindre rømming må effektiviseres og forbedres. Hvisdette ikke er mulig kan sterilisering av oppdrettslaksen blinødvendig.

Vi tror at hvis resultatene av forskningen som blepresentert på dette symposiet og de to tidligere erkorrekte, og at hvis ikke betydelige tiltak blir satt inn,risikerer vi tap av lokal tilpasning og diversitet av den villelaksen i Nord Atlanteren. Dette kan ha betydeligekonsekvenser for villaksens overlevelsesevne, produktivitetog evnen til å overleve forandringer i miljøet.

Lars Petter Hansen (ICES Co-Convener) og

Malcolm Windsor (NASCO Co-Convener)

6 October, 2006

1

1INTRODUCTION

The River Imsa, Norway where life-cycle experiments with farmed and wild salmon and their crosseshave contributed to understanding the interactions between wild and cultured salmon.


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1. Introduction1.1 Background

Paradoxically, at a time when there is serious concernabout the status of wild Atlantic salmon stocks, theabundance of salmon in the North Atlantic Ocean hasprobably never been higher as a result of the rapid growthof salmon farming.

Since the early 1980s, farming of Atlantic salmon hasbecome a major industry, with production in 2005 ofapproximately 785,000 tonnes in the North Atlantic, areduction compared to 2004 (831,000 tonnes) but a 5%increase on the previous five-year mean production. Mostof this production occurred in Norway (72%) andScotland (17%). The provisional worldwide production in2005 was approximately 1.3 million tonnes with Chileproducing approximately 405,000 tonnes. The worldwideproduction of farmed Atlantic salmon is approximately600 times the reported catch of salmon in the NorthAtlantic (ICES, 2006a). Progress is being made inmanaging the interactions between wild and farmedsalmon, and collaboration between wild and farmedsalmon interests is improving (Anon, 2006). However, thewild stocks are in a weakened state and vulnerable to awide range of anthropogenic impacts. There are,therefore, concerns about the disease, parasite, genetic,and ecological impacts of salmon farming on wild salmonstocks (Hansen et al., 1991; Hutchinson, 1997;Youngson etal., 1998; Hutchinson, 2006). A regime is required thatallows the industry to prosper but, at the same time,safeguards the wild stocks so as to maintain the social andeconomic benefits from both wild and farmed salmon.This has not been, and will not be, easy. Currently, theAtlantic salmon is to the fore but, as aquaculture developsand diversifies into other species, the wild stocks of theseand other species may be affected, and the nature ofinteractions may be similar.

Interactions between cultured and wild salmon are notrestricted to those arising from salmon farming. Inresponse to the decline in the abundance of wild salmonstocks, cultured fish are stocked for mitigation, restoration,and rehabilitation purposes. Furthermore, although‘commercial’ ranching of salmon is no longer undertakenin the North Atlantic, there is interest in ranching tosupport recreational fisheries in some rivers. A regime isrequired under which the risks as well as the benefits arecarefully considered before deliberately releasing anycultured fish into the wild.

In response to concerns about interactions betweensalmon aquaculture and the wild salmon stocks, a series ofinternational meetings aimed at reviewing scientificunderstanding of interactions and providing guidance onappropriate management responses has been convened.The first major international symposium on this subject,sponsored by the Norwegian Directorate for NatureManagement and NASCO, was held in Loen, Norway, in1990 (Hansen et al., 1991). NASCO was sufficientlyconcerned by the gravity of the threats and theirpotentially irreversible nature that, in 1991, it adoptedguidelines designed to minimise impacts of aquaculture onthe wild stocks. These guidelines were replaced threeyears later by the Oslo Resolution, which in turn wasreplaced in 2003 by the Williamsburg Resolution(NASCO, 2006a). This Resolution was developed toensure that the measures taken by NASCO Parties andtheir relevant jurisdictions to minimise the impacts ofaquaculture, introductions and transfers, and transgenicswere consistent with the Precautionary Approach. Thedevelopment of the Williamsburg Resolution drew oninformation presented at a second major internationalsymposium, convened by ICES and NASCO, held in Bath,England, in 1997, which reviewed the scientific andmanagement aspects of interactions between salmonculture and the wild salmon stocks (Hutchinson, 1997;Youngson et al., 1998).

Since the first symposium in 1990, production of farmedsalmon in the North Atlantic has more than trebled.Aquaculture is certainly not the only threat to the wildsalmon stocks, and NASCO is addressing a wide range ofother issues relating to salmon conservation andmanagement (e.g. the management of fisheries and habitatprotection and restoration) and has recently establishedan International Atlantic Salmon Research Board toinvestigate the factors influencing the mortality of salmonat sea and the opportunities to counteract them. TheBoard has recently endorsed an ambitious internationalprogramme of research, the SALSEA programme,containing a comprehensive mixture of freshwater,estuarine, coastal and offshore elements, ensuring athorough overview of factors which may affect themortality of Atlantic salmon at sea.

NASCO and ICES believe that the progress now beingmade in managing the interactions between wild andcultured salmon must be maintained, enhanced, and givenmore urgency to ensure that all aquaculture practices areconducted in a sustainable manner that does not threatenwild stocks. They therefore agreed to hold a third


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international symposium in Bergen, Norway, during 18 - 21October 2005.

This publication forms the report of the Bergensymposium. It is intended to serve as a record for ICESand NASCO of the symposium and of the Conveners’conclusions, which have been based on all the informationpresented. It also represents a report to the sponsoringorganizations and a record of the state of internationalknowledge of this subject in 2005, the challenges thatremain in managing interactions between cultured andwild salmon and possible solutions to these challenges, andit provides recommendations for future researchrequirements. The intention is that this report will bemade widely available to those involved in the culture ofsalmon, to managers of wild salmon stocks and to thoseinvolved in research on interactions between wild andcultured fish.

A second publication containing those scientific papersaccepted following peer review has been published as aSpecial Symposium Volume of the ICES Journal of MarineScience that has been guest-edited by Dr PeterHutchinson (Hutchinson, 2006).

1.2 Objectives of the Symposium

The objectives of the symposium were:

(i) to summarise available knowledge of the interactions between aquaculture and wild salmon stocks and other diadromous fish species;

(ii) to identify gaps in current understanding of these interactions and to develop recommendations for future research priorities;

(iii) to review progress in managing interactions, the remaining challenges, and possible solutions; and

(iv) to make recommendations for additional measures to ensure that aquaculture practices are sustainable and consistent with the Precautionary Approach.

The aim of the symposium was to build on the existingcollaboration between wild and farmed salmon interestsso as to identify the remaining challenges and possiblesolutions in moving toward sustainable culture of Atlanticsalmon. As such, the focus was on practical approaches tomanaging interactions between wild and cultured salmon.

1.3 Structure of the Symposium

Ms Janne Sollie, Director General of the Directorate forNature Management in Norway, opened the symposiumwhich was structured into four plenary sessions and a

poster session. In total, 4 keynote papers, 35 invited andcontributed papers and 13 poster papers were presented.The abstracts of these papers are contained in Annex 1.

The first of the plenary sessions was a keynote sessionintended to set the scene with reviews of the value ofwild Atlantic salmon, developments in the sustainability ofthe salmon farming industry, the stock status andmanagement of wild Atlantic salmon, and the ecology ofcultured Atlantic salmon and their interactions with wildfish. Following this keynote session there were plenarysessions focusing on genetic and ecological interactionsand their management, and on disease and parasiteinteractions and their management. The final plenarysession was a synthesis session intended to highlight theremaining challenges and their possible solutions.Following summaries of the three plenary sessions (seeAnnexes 2 - 4) and poster session (see Annex 5) by theCo-Chairmen, six participants from different interestswere asked to give their perspectives on the informationpresented during the symposium, i.e. their ‘take-home’messages (see Annex 6). There were two representativesof non-governmental organizations, two representatives ofthe fish farming industry, and two representatives ofadministrations involved in the management of salmonfarming or wild salmon. There was then a general periodof discussion.

The symposium was closed by Mr Peter Gullestad,Director of the Norwegian Directorate of Fisheries and aVice-President of ICES.

About 110 participants from 15 countries attended thesymposium, including delegates with experience ofresearch into, and management of, interactions betweencultured and wild salmon in the North Atlantic Ocean,Baltic Sea and North Pacific Ocean. A list of participantsis given in Annex 7.

1.4 Acknowledgements

The Conveners express their sincere thanks to thesymposium Steering Group: Dr Malcolm Beveridge, MsMary Colligan, Professor Tom Cross, Mr Knut Hjelt, DrPeter Hutchinson, Mr Arni Isaksson, Mr Geoff Perry, andMr Chris Poupard. We would also like to thank Dr PeterHutchinson for his assistance in preparing this report andMs Margaret Nicolson and Ms Bente Halsteinsen foradministrative support. The Conveners also thank theparticipants who provided their take-home messagesduring the final session: Ms Katherine Bostick, Ms FionaCameron, Mr Knut Hjelt, Dr Jens Christian Holm, Mr James


3

Ryan, and Mr Øyvind Walsø. The details of the affiliationsof those mentioned here and elsewhere in this report aregiven in Annex 7.

Finally, ICES and NASCO acknowledge with gratitude thegenerous support of the following organizations: ResearchCouncil of Norway, Directorate for Nature Management(Norway), Directorate of Fisheries (Norway), NorwegianInstitute for Nature Research, Royal Norwegian Ministry ofFisheries and Coastal Affairs, Royal Norwegian Ministry ofthe Environment, Scottish Executive, DEFRA (UK),Fisheries and Aquaculture Research Fund (Norway),Directorate of Freshwater Fisheries and SalmonidEnhancement Fund (Iceland), National Marine FisheriesService (USA), the Worshipful Company of Fishmongers(UK), Atlantic Salmon Trust (UK), Intervet International BV(the Netherlands), Marine Institute (Ireland), Pharmaq AS(Norway), ScanVacc AS (Norway), Norwegian FarmersUnion, Norwegian Salmon Rivers, and the City of Bergen.


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2OVERVIEW OF THE MEETING

Photograph courtesy of the Scottish Salmon Producers’ Organisation.

2. Overview of the Meeting2.1 Session1: Opening Addresses and Keynote

Presentations

The symposium was opened by Janne Sollie, the DirectorGeneral of the Directorate for Nature Management, whonoted that while the topics on the symposiumprogramme were similar to those at the Loen and Bathmeetings in 1990 and 1997, respectively, the situation hadchanged because of the significant growth of the salmonfarming industry since 1990 and the continuing decline inwild stocks. She noted that it is now recognised thatsalmon farming can pose serious threats to the wild stocksand that while progress has been made in managingimpacts and in improving cooperation among the salmonfarming industry, the authorities and various stakeholders,additional measures are required in order to movetowards sustainable culture of Atlantic salmon. To highlightthis she referred to two events in Norway in 2005 thathad resulted in 600,000 farmed salmon escaping to thewild.

ICES and NASCO representatives then highlighted theimportance of the topic of the symposium to theirorganizations, challenging the participants to urgently findsolutions to the real problems that remain in managinginteractions between cultured and wild salmon.

The first keynote presentation by Pat O’Reilly highlightedthe social and economic values of wild Atlantic salmon. Inaddition to the very significant values associated with thefisheries and eco-tourism, the symposium was remindedthat the Atlantic salmon has a high profile and the generalpublic care about conserving the resource even if they donot use it. He noted that there are many pressures onthe wild salmon stocks, which are extremely vulnerablegiven their present status, and that while there has beenprogress in minimising impacts of salmon farming,containment is not adequate given the growth inproduction. He indicated that the continuing escape offarmed salmon to the wild poses risks of genetic damageto the wild stocks, which would not be in the salmonfarming industry’s long-term interests because the diversitypresent in the wild stocks is the industry’s seed corn. Hebelieved that if the industry is perceived to be damagingthe wild salmon stocks, consumers may reject its products.

The second keynote presentation by Helge Midttunfocused on the development of the salmon farmingindustry since the 1960s and its importance to coastalcommunities around the North Atlantic and elsewhere.

Worldwide production of farmed salmon has trebled inthe last ten years but he stressed that the continuedsuccess of the industry will require that it is conducted inharmony with the environment and that where conflictsarise, these are resolved through cooperation andplanning. He indicated that while the industry hadaddressed environmental concerns with regard to effluentsof nutrients and organic matter, and antibiotic usage hadbeen dramatically reduced, the level of escapes remainstoo high relative to the abundance of the wild stocks,although around 98% of all farmed salmon are successfullycontained. He concluded that for the salmon farmingindustry to continue its growth, the product must beperceived to be safe and healthy, the industry must not beassociated with damage to the natural environment, andthe industry should be seen to be open and transparentand willing to focus on animal welfare and environmentallysustainable practices.

In the third keynote presentation Walter Crozier reviewedthe status and management of wild salmon stocks. Allfour European stock complexes were considered by ICESto be outside precautionary limits in 2004 and in NorthAmerica 31% of monitored rivers achieved less than 50%of their conservation limits. Some stocks are criticallyendangered and the projections for stock rebuilding forlow productivity stocks are very long-term. He referredto the wide range of pressures on wild salmon stocks,including habitat loss and degradation, pollution, predation,climate change effects, and interactions with culturedsalmon. Progress is being made in reducing exploitationand in addressing other factors, but the clear message wasthat given the status of the wild stocks, it is essential thathuman activities do not exacerbate the situation.

The fourth and final keynote presentation by Bror Jonssonprovided a comprehensive review of the literatureconcerning the ecology of cultured Atlantic salmon innature and their interactions with wild salmon. Heconcluded that cultured salmon compete for food, spaceand breeding partners with wild salmon in nature and thattheir performance and reproductive success in nature arevariable but can be much poorer than those of wild fish ofsimilar size. The reduced fitness is the result ofmorphological, physiological, ecological and behaviouralchanges that occur in hatcheries. The success of culturedfish increases with the amount of time they have spent innature. Cultured fish may, through density-dependentmechanisms, displace wild fish, increase their mortality andreduce their growth rates, with effects on associated life-history traits, biomass and production. He highlighted the


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need for further research on the factors influencing theperformance of hatchery fish in nature and the ecosystemeffects of increasing salmon abundance in fresh and seawater.

2.2 Session 2: Genetic and Ecological Interactions and their Management

This session comprised twenty presentations. The topicsaddressed were modelling studies of genetic andecological impacts; environmental impacts of salmonfarming in Chile; selection programmes in aquaculture; thelevel and causes of escapes and incidence of escapees inthe wild; behaviour of escapees; physical and biologicalcontainment of farmed salmon; genetic impacts ofescapees; stocking programmes; striped bass/salmoninteractions and genetic stock identification.

Modelling studies

Two presentations reported on modelling studies. Sincethe Bath symposium there has been significant progress intwo areas related to genetic and ecological interactions.First, genetic methods to distinguish individuals andpopulations have been refined and genetic information onboth wild and farmed salmon populations has increased.Second, studies on the spawning success and survival offarmed and wild salmon and their crosses have beencompleted in the Rivers Imsa (Norway) and Burrishoole(Ireland). Data on relative fitness and spawning success ofwild and cultured salmon were used to model the geneticand ecological effects of farmed salmon on wild salmonunder various intrusion scenarios. The model suggeststhat with a fixed intrusion rate of 20% escaped farmedsalmon at spawning, substantial changes take place in wildsalmon populations within ten salmon generations. Lowintrusion scenarios (varying from 0 to 25% per year)suggest that farmed offspring are unlikely to becomeestablished in the population, while under high intrusionscenarios (varying from 0 to 75% per year), the modelsuggests that the wild salmon populations eventuallybecome mixtures of hybrid and farmed descendants. Thelow and high intrusion scenarios were based on theincidence of escapees found in Norwegian rivers. Themodel also indicated that recovery is not likely under allscenarios, even after many decades with no furtherintrusions, and the authors concluded that furthermeasures to reduce escapes of farmed salmon, and theirspawning in the wild, are required urgently.

Population dynamic modelling using data on catches,returns, juvenile densities and escapements was used to

estimate the impacts of marine salmon farming on survivalof wild salmonids using populations less exposed tofarming as controls. While there are significant challengesin analysing these data (including data quality, a high degreeof natural variability and missing data), impacts on thesurvival of wild fish related to the scale of farmed fishproduction in the area were identified.

Environmental impacts of salmon farming in Chile

A review of the impacts of Atlantic salmon farming onmarine coastal ecosystems in Chile indicated that whenthis subject was last reviewed in 1996, the evidence didnot suggest significant impacts. Today, the industry isconsidered to be consolidated but with potential forfurther expansion to the south into pristine coastal areas.After almost ten years of sustained growth, recentresearch indicates a significant loss of benthic biodiversityand localised changes in physico-chemical properties ofsediments in areas with salmonid farms. The presence offarms was also found to increase the density ofdinoflagellates and the abundance of omnivorous andcarrion-feeding sea birds. Farmed salmon escapees arealso a concern in Chile. The authors concluded that it isurgent that an ecosystem approach is implemented toassess and manage all impacts from salmonid farming inChile.

Selection programmes in aquaculture

In a review of the history of genetic research within theaquaculture industry it was reported that the goal withinthe Norwegian aquaculture industry is domestication toimprove production performance by reducing mortalityand increasing growth rate. Both mass selection (selectingindividual fish out of the entire population) and familyselection (selecting particular families out of thepopulation) are used but less than 5% of fish stocked inaquaculture originate from selection programmes. Mostof the genetic improvement is based on mass selectionwithout any pedigree information. Mass selection can onlybe used to improve traits recorded on breedingcandidates (e.g. growth rate, shape, colour, grilse or multi-sea-winter fish) whereas family breeding is required toimprove meat and carcass quality and resistance todiseases and parasites. In future, focus areas for breedingprogrammes will include use of selective breeding todevelop strains of salmon capable of utilizing vegetableoils, to develop more robust strains with high survival andgood production performance in farming and to reducethe fitness of escapees for survival in the wild.


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Level and causes of escapes and incidence of escapees in thewild

Five presentations focused on the level and causes ofescapes and the incidence of escapees in the wild.

In Norway, the causes of escapes are categorised as:technical failure, towing of cages, handling errors,predators, floating objects, damage by boat propellers, andescapes during smolt production. Since 1997, thereported number of escaped farmed salmon has variedbetween 200,000 and 500,000 fish annually. These areminimum estimates. The industry accepts that thesenumbers are too high and is working towards a level ofescapes that is as close to zero as practicable. Norwegianfarmed salmon producers have a ‘National Action Plan toPrevent Escapes’ which focuses on preventative measuresfor all causes of escapes. Some elements of the plan applyto all installations but there are separate elements dealingwith smolt/fry production, on-growing facilities,slaughterhouses and well-boats. The plan includeselements for improvement such as information andeducation, internal control systems, environmentalmanagement systems and stronger responses from theauthorities in relation to negligence. Most of this actionplan has been implemented in regulations and theNorwegian salmon farming industry has investedconsiderably in research and development projects aimedat reducing escapes.

While information is reported on large-scale escapes frommarine facilities in most countries, the scale of smaller butmore frequent ‘trickle losses’ (for example during handling,net changes, fish transfers, etc.) remains unquantified.Furthermore, there may be escapes from freshwaterhatcheries. A study from Canada involved monitoring forescaped juvenile farmed salmon in the proximity of morethan 90% of commercial hatcheries producing salmonsmolts at locations next to freshwater streams in NewBrunswick. Escaped juvenile farmed fish were recorded at75% of the sites sampled, although numbers varied by siteand year. The results highlight the need forimplementation of an effective containment strategy forfreshwater hatcheries, and the authors concluded that thisshould be readily achievable.

The detection of European ancestry in escaped farmedsalmon was reported from two sampled rivers in NewBrunswick. The use of European strains for commercialculture by the salmon farming industry has never beenpermitted in either Nova Scotia or New Brunswick.However, the authors concluded that their findings

highlight the need for improved containment strategies forfreshwater hatcheries and for genetic screeningprogrammes for salmon farming broodstock to minimisethe likelihood of introgression of non-local geneticmaterial into severely depressed wild salmon populationsin the Bay of Fundy region.

A study in Norway examined the relationship betweenthe frequency of farmed salmon in wild populations andfish farming activity. The data revealed a significant positivecorrelation between the incidence of escaped farmedsalmon in rivers and the number of farmed salmon in netpens at the county level, suggesting that protection areasmay reduce the impact of escapees in nearby wild salmonpopulations. The lack of a significant correlation betweenthe incidence of farmed salmon relative to the reportednumber of escaped farmed salmon suggests that thereported statistics underestimate the number of escapedfish owing to under-reporting or non-reporting (e.g. ofsmall-scale ‘trickle losses’) of some escape events. Areduction in the correlation coefficient for the relationshipbetween the stock of farmed salmon and the incidence ofescaped farmed salmon in rivers over time suggests thatthere may have been a reduction in the number of smoltsand post-smolts escaping from farms in recent years. Fishescaping at these stages would be expected to ‘home’ tothe area of escape.

A paper from the UK and Ireland reviewed thedevelopment and results of monitoring programmes forthe incidence of escaped farmed salmon in rivers andfisheries. Escapees have occurred at varying frequenciesand intervals in coastal and freshwater fisheriesthroughout Scotland and Ireland and in northwest Walesand England. While escapees occur at generally lowfrequencies in fisheries in Scotland, they have beenreported at far higher frequencies in some areas in someyears (22% in coastal fisheries and 19% in freshwaterfisheries). Similarly, in Northern Ireland escapees occur atan average level of 4.2% and a maximum of 13.8%.However, in Ireland the frequency of escapees is low in allregions, with an average of <0.1% to 0.6%, and amaximum frequency of 2.2%. No escapees werereported in fisheries in England and Wales in 2003 or2004 but in 2001, following an escape event in NorthernIreland, escapees comprised up to 19.4% of coastalcatches and 30% of catches in freshwater fisheries. Theauthors assessed the effectiveness of the monitoringprogrammes and made recommendations for theirimprovement. In particular, it was noted that ideally datashould be collected by scientific sampling from in-river


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stocks and from fishery-independent sources and thatmonitoring should be primarily targeted in regions wheresalmon farms are situated.

The results of a pilot study to trace the farm of origin ofescaped salmon using microsatellite DNA and geneticassignment tests indicated that escaped farmed salmoncould be assigned with a high degree of accuracy (>90%)to farm strain, but with lower accuracy (67%) to farm oforigin. The study suggests that genetic markers havepotential for tracing the farm of origin of escaped farmedsalmon but further work is required.

Behaviour of escapees

Three papers provided information on the behaviour ofescaped farmed salmon, two of which involved tagging andrelease of farmed fish.

In the Bay of Fundy, Canada, acoustically tagged farmedsalmon were found to disperse rapidly (within a fewhours) beyond 1km from the release site, suggesting thatrecapture efforts may be unsuccessful in environmentssubject to major tidal influence. Many of the tagged‘escapees’ were assumed to have been preyed upon byseals. None of the tagged fish were detected in any of themonitored salmon rivers draining into the Bay of Fundy.However, in the past, farmed salmon are known to haveentered rivers in the region following large-scale escapeevents.

In Norway, large farmed salmon tagged prior to releasedid not appear to home to their release site and theirdistribution appeared to be related to ocean currents.The survival and distribution of the tagged ‘escapees’depended on the time of year of the escape, with salmonreleased in the autumn, one year prior to sexualmaturation, surviving poorly, whereas those released in thewinter and spring showed higher survival. It washypothesised that salmon escaping during the autumn aretransported with currents to Arctic areas and do notsurvive the winter, and that salmon escaping during thewinter and spring move with currents and may enterhomewater fisheries and spawning populations far fromthe site of release when they mature.

A second study from Norway indicated that escapedfarmed female salmon spawned in four out of six riversstudied. The proportion of successful farmed spawners inthese rivers varied from 0 - 83% among rivers and yearsand was positively correlated to the proportion of farmedfish in autumn catches and negatively correlated to thedensity of wild fish. At high densities of wild fish, farmed

salmon appeared to be excluded from spawning, probablythrough breeding competition.

Physical and biological containment of farmed salmon

In Norway the objective of the salmon farming industry isto reduce escapes to a level at which they pose no risk tothe wild stocks. New cage designs and mooring systemswere described that are intended to reduce theprobability and consequences of accidents both withregard to technical failure and incorrect use and operationof equipment.

The use of sterile farmed salmon (all-female triploid fish)would prevent spawning of escaped farmed fish in thewild, eliminate farm production losses associated withearly maturation and protect investments made indeveloping novel genotypes. The pros and cons of usingsterile salmon in aquaculture were described. The massproduction of all-female triploid salmon is easy to achieveat a commercial scale, and inexpensive, although there aresome logistical issues concerning broodstockrequirements. There is abundant evidence that this is aneffective method of eliminating maturation and preventingspawning of farmed fish in the wild. However, there areseveral problems with regard to the performance of all-female triploid fish in aquaculture, which can include areduced ability to withstand chronic stress and anincreased incidence of deformities. Maximising theperformance of triploid fish requires a clear understandingof their biology and a long-term commitment to selectivebreeding based on triploid production characteristics anda clearer understanding of their biology. The authorconcluded that until this is done, the true advantages anddisadvantages of sterile salmon will not be known.

Genetic impacts of escapees

A study of temporal stability in Atlantic salmonpopulations in Norway indicated that significant geneticchanges were observed in three of seven study rivers,probably as a result of gene flow from farmed salmonwhich have been reported from these rivers in largenumbers. There was also some evidence of diminishinggenetic differentiation among populations.

Stocking programmes

Three papers reviewed various aspects of stockingprogrammes. A review of the Pacific salmon hatcheryprogrammes on Hokkaido Island, Japan, suggested thatmore effective use of stocking programmes would requiremore specific evaluation of the benefits of theseprogrammes and comparison of the benefits to other


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management approaches, such as harvest controls andhabitat rehabilitation. It was concluded that adaptivelearning approaches should be utilised for hatcheryprogrammes to minimise the risks associated with themand to promote sustainable wild stocks.

A study from rivers in France and Spain indicated a loss ofregional population structure in wild Atlantic salmonpopulations. Significant genetic differentiation betweenneighbouring rivers, typical in Atlantic salmon, that existedprior to stocking, was lost after only a decade of stockingwith salmon of foreign origin. The authors concluded thattheir findings highlight the risks to the genetic diversity ofwild stocks subjected to stocking with foreign-originmaterial.

In the period between 1995 -1999, approximately800,000 reared salmon from two Baltic salmon strainswere released at the islands of Bornholm and Møn in theBaltic Sea. Estimates of straying of ranched Baltic salmoninto rivers on the Swedish west coast, based on tagrecaptures, indicated that the proportion of releasesrecaptured outside the Baltic was low (on average 2%).The proportion of straying salmon in rivers on the westcoast of Sweden varied between years and among rivers.However, the ranching programme had been discontinueddue to concern about deleterious effects on the wildpopulations.

Striped bass/salmon interactions

A paper from the US described the implications of thesuccessful stock rebuilding programme for striped bass onpopulations of Atlantic salmon and other anadromousspecies. Moderate to strong negative correlations werefound between estimates of the abundance of stripedbass, a known predator of salmon smolts, and returns ofsalmon to New England rivers. Further research isrequired to quantify the proportion of smolt productionconsumed by striped bass, particularly for salmonpopulations listed under the Endangered Species Act.

Genetic stock identification

Genetic stock identification methods have been used tomonitor changes in wild and hatchery proportions ofAtlantic salmon in Finnish catches in the Baltic Sea. Theproportions of seven stock groups, important to fisheriesmanagement, were assessed in catch samples takenbetween 2000 and 2005. For example, in the Gulf ofBothnia area, the proportion of wild fish showed anincreasing trend in all areas until 2003, mainly because ofthe decrease in total catches caused by the relatively

greater mortality of hatchery-reared fish compared withwild fish. In 2004, the total number of wild fish caught hadalso increased, indicating an increase in the abundance ofwild stocks. The threatened eastern Estonian and Russianwild stocks were recorded only in the western part of theGulf of Finland, where the proportion of wild fishincreased from 9% in 2003 to 19% in 2004.

2.3 Session 3: Disease and Parasite Interactions and their Management

This session comprised fifteen presentations, many ofthem focusing on the biology and control of sea lice andtheir impacts on wild stocks.

Overview of diseases in farmed and wild salmon

A review of parasitic agents affecting Atlantic salmon, fromviruses and bacteria to ectoparasites, concluded thatepidemics can affect both farmed and wild fish and haveconsequences for both: population regulation in wild fishand economic damage and welfare effects in farmed fish.Wild fish are the ultimate source of parasites and can alsobe reservoirs for infection which impede eradicationprogrammes in farms, but farming can exacerbate diseaseproblems through promoting conditions favouringepidemics, long-range transport and spill-over back intothe wild. It was noted that epidemics among farmedpopulations do not necessarily result in epidemics amongwild fish populations, highlighting the importance of goodbio-security and husbandry in mitigating risk.

Sea lice biology, impacts on wild stocks, and control

A review of the biology and genetics of sea lice, focusingon research conducted since the last major review of thesubject in 1999, concluded that research on sea lice hasdeveloped considerably, and genetic techniques are nowbeing applied to increase understanding of sea lice lifehistory and biology. Information on the developmentalstages under different environmental conditions, thebehaviour, distribution and dispersal of free-living stages,monitoring practices and population structure hasincreased, and modelling studies have been undertaken.Molecular genetics work also raises the possibility ofdeveloping a vaccine against sea lice.

An investigation into how sea lice infestations affect thephysiology of wild sea trout was described. Since 1989sea trout stocks on the west coast of Scotland havedeclined catastrophically, accompanied by the ‘prematurereturn’ to fresh water of post-smolts typically bearingheavy sea lice infestations. Laboratory studies wereconducted to assess the sea lice infestation levels that


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trigger sub-lethal, chronic and acute physiological stress insea trout. A threshold level of thirteen lice per fish wasdetermined.

A study into the susceptibility of wild, farmed and wild-farmed hybrid Atlantic salmon to sea lice, furunculosis andInfectious Salmon Anaemia (ISA) concluded that therewere no large and systematic differences in susceptibilitybut the topic merits further research.

A review of the impacts of sea lice on farmed and wildsalmonids concluded that sea lice must presently beregarded as a potentially important population-regulatingfactor in many salmonid stocks. Methods to assessinfestation levels on migrating post-smolts have beendeveloped. Pest management measures introduced by thefarming industry to reduce the number of sea lice larvaein salmon farming areas are probably of most benefit tosalmon stocks. Reference was made to the highinfestation pressure imposed by farms on wild stocks inmany areas and the inverse relationship between theincidence of lice on wild sea trout and distance from fishfarms.

Concerns about the impacts of sea lice from Atlanticsalmon farming on wild salmonids are not restricted tothe North Atlantic area. Farming of Atlantic salmon in theBroughton Archipelago area of British Columbia has givenrise to concerns that sea lice from the farms may haveresulted in high mortality of pink salmon. In 2002,concern had been expressed that the low return of pinksalmon was the result of sea lice infestation and led to theintroduction, in 2003, of a Provincial Action Plan thatestablished a fallowed migration corridor for pink salmonand mandatory monitoring of sea lice. A study presentinginformation on marine mortality of pink salmon fromrivers in this area indicated exceptional survival of pinksalmon migrating to sea in 2003 but it was not possible toconclude whether this was due to the introduction of aProvincial Action Plan, increased freshwater flow whichcould lead to conditions less favourable to sea liceproduction, or other effects.

A study involving the treatment of Atlantic salmon smoltswith emamectin benzoate (SLICE®) prior to releaseindicated that survival did not differ between treated andcontrol groups released in May but there was a two-foldincrease in survival in treated compared to control groupsreleased in June. Furthermore, one-sea-winter fishreturning from the treated groups were about 15%heavier than controls and the authors concluded thatinfestation levels changed from non-lethal to lethal during

the smolt migration period and that sub-lethal lice levelsmay affect growth, size at spawning and, consequently,fecundity of wild fish.

Studies of sea lice dispersal and behaviour are crucial tounderstanding the infestation pressure that sea lice infarms pose for wild salmonids and two presentationsexamined these aspects. Weekly plankton samples fromLoch Shieldaig in Northwest Scotland indicated anincrease in larval densities during the farm productioncycle, followed by a decrease as the farms harvested andwere left fallow. Nauplii showed no preference for depthbut significantly greater densities of copepodids wererecovered at the surface than at depth. The densities oflarvae varied considerably over the two-year samplingperiod.

A study from Norway examined the effects of bothhydrography and lice abundance on infestation rate ofAtlantic salmon and sea trout smolts emigrating from twocontrasting fjord systems in Norway. Differences ininfestation pressure between the two fjords were foundand, in addition, within a system, year-to-year differences inhydrography could cause changes in sea lice dispersionthat markedly altered infestation risks to wild fish. In theAltafjord, infestation levels on migrating salmon post-smolts were not high enough to cause problems, and inthe Sognefjord the infestation levels declined in responseto treatments by salmon farmers at the critical time in thespring. However, reductions in infestation intensity werenot found for sea trout in either fjord. It was concludedthat wild and farmed salmon can coexist in Norwegianfjords if appropriate lice management strategies are used.

Aquaculture impacts on disease resistance

A study from the Burrishoole system in Ireland examinedthe impacts of disease associated with aquaculture on thegenetic variability of sea trout by examining variations at alocus critical to immune response (MHC1) and six neutralmicrosatellite loci before and during aquaculture activities.A decrease in genetic variability at the MHC1 locus wasobserved, indicating a selective response that was notmirrored by similar reductions at neutral loci. Thisdecrease corresponded with aquaculture activitiescommencing in the catchment. Subsequent recovery invariability seen among later samples may reflect anincreased contribution by resident brown trout to the seatrout stock.

Health management

Four presentations focused on health management


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practices. A review of health management practices inScottish salmon farms indicated that bacterial diseases arelargely under control due to use of vaccines but viraldiseases remain a serious concern. Management measuresand access to efficient medicines have been successful inreducing sea lice levels in farm salmon but more progressis required. A key message was the threat posed by theemergence of new diseases but the potential of geneticselection to improve disease resistance, the emerging fieldof nutrachemicals (dietary supplements) and thecontinued importance of application of best practice toavoid disease problems were highlighted.

A review of trends in the use of medicines in Norwegiansalmon farming concluded that there were notoxicological risks to wild fish from drugs used in thesalmon farming industry. The use of inadequate licetreatments can result in heavy lice infestations andincreased mortality of emigrating salmon and sea troutsmolts. However, extensive sea lice treatment increasesthe risk of resistance developing and may represent anincreased risk to wild salmonids.

A review of the use of ‘cleaner’ fish to control sea lice onfarmed fish indicated that wrasse are widely used inNorwegian salmon farms and that techniques to culturewrasse are now developing. The study found that giventhe correct conditions wrasse are one of the most cost-effective and environmentally benign ways to control sealice. Wrasse prefer to feed on pre-adult lice andparticularly adult female lice. Lice eggs do not survivepassage through the wrasse digestive system. The authorsconcluded that wrasse should, therefore, be considered aspart of an integrated sea lice management strategy.

In Scotland, a Tripartite Working Group providing a forumfor cooperation among regulators, farmers and wild fishinterests has been established and has resulted in thesharing of information and the development andimplementation of area management agreements (AMAs).AMAs provide local solutions to maximise theeffectiveness of sea lice management and to control andreduce escapees. Twenty areas in three regions ofScotland were targeted and eighteen agreements wereexpected to be in place by the end of 2005. Thisapproach has improved communication among the partiesinvolved, although it is too early to draw conclusionsabout the benefits to wild salmonids.

Gyrodactylus salaris

The last paper in the session reported on the introduction

and spread of Gyrodactylus salaris. The parasite wasintroduced to Norway in 1975, probably through theimportation of smolts from the Baltic, and has dramaticallyreduced stocks of salmon in 45 rivers. The parasite isknown to be present in Denmark and Germany and islikely to have been introduced to other Europeancountries with movements of live rainbow trout, althoughthe UK and Ireland are free of the parasite. In Norway, anaction plan has been developed involving surveillance,prevention of spread to other rivers, eradication andrestoration. 27 of the 45 infected rivers have beensuccessfully treated and there is growing use of acidifiedaluminium as a treatment method in addition tocontinuing use of rotenone. The dangers posed by livefish movements, particularly of rainbow trout, and theimportance of international cooperation to prevent thefurther spread of the parasite were highlighted. For theUK and Ireland preventing the importation of the parasiteis the major objective.

2.4 Session 4: Poster Session

This session comprised a total of 13 presentationsfocusing on studies of the abundance, distribution,behaviour and source of escapees; the biology of sea liceand genetic aspects of stocking programmes. There werealso posters on aquaculture-free zones, the comparativefeeding behaviour of juvenile cultured and wild salmon andthe effects of domestication on the growth, behaviour andphysiology of fish.

Escapees

Sampling in the River Teno (Tana River), a border riverbetween Norway and Finland, in the period between1987 - 2004 indicated that escapees made up a smallproportion (0.08 - 0.53%) of the catch during the fishingseason. However, small samples collected after the closeof the fishing seasons in six years suggested higherproportions of escapees in some years, raising concernsabout the genetic impacts on native salmon populations.

Research in Norway involving acoustic tagging of farmedsalmon ‘escapees’ showed that several of the tagged fishremained in the vicinity of the escape site after severalweeks, suggesting that it may be possible to recaptureescapees, although these findings contrast with the resultsof studies in the Bay of Fundy (see section 2.2) where thefish moved rapidly away from the release site.

A second study in Norway using catch data from a gill netfishery conducted after the fishing seasons for salmon andsea trout indicated that there was a low incidence of wild


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fish in the catches and, provided that the conservationstatus of local wild salmonid stocks is taken into account,such a fishery may reduce the number of escapees, thuslowering the risk of introgression with wild salmonidpopulations and removing potential sources of sea lice,and provide information on relative abundance ofescapees in the sea.

A third presentation from Norway described a study, the‘TRACES’ project, that is being conducted in theHardangerfjord to examine the costs and efficiency ofidentifying and tracing the origin of farmed salmon. In2003, a national Committee had been established inNorway to identify methods to trace the origin ofescaped farmed salmon and had concluded that nomethods were ready at that time for implementation. Twomethods were, however, identified that merited furtherinvestigation: coded-wire tagging and a ‘contingencyapproach’ based on the characteristics of the fish. In the‘TRACES’ project, DNA microsatellite markers, singlenucleotide polymorphisms, fatty acid profiles, traceelement and stable isotope composition were assessedwith regard to their utility in tracing the farm of origin ofescapes.

A study involving acoustic tracking of wild cod found thatthey occurred in the exit corridors of wild salmon smoltsfrom critically endangered salmon rivers in the Bay ofFundy. The authors expressed concern that as field trialsrearing farmed cod are now underway, escapees from codfarms might behave like the wild cod in their study, andthey could prey on wild salmon smolts. The authorsconcluded that there is a need for careful consideration tocage design and siting so as to avoid interactions with wildcod and with wild salmon and other diadromous species.

Sea lice biology

Two posters presented information on sea lice biology.The first examined the infestation success of sea lice atdifferent temperatures ranging from 6 - 16oC and showedthat lice were infectious for a longer period of time at lowtemperatures. These data are important in modelling thedispersal and survival of free-living lice larvae.

The second presentation examined the role of freshwateracidification on the sensitivity of salmon smolts to sea lice.Many rivers in southern Norway can be periodicallyacidified to sub-lethal levels and additionally there aremany fish farms in the region. This study concluded thatthe combined effects of moderate acidification in freshwater and moderate sea lice infestation in sea water can

have the same negative effect as higher acidification orhigher lice infestation. The authors concluded that there isa need, therefore, to consider the effects of multiplestressors on smolt survival rather than using single-factormodels.

Stocking programmes

A study from the rivers Ulla and Lerez in Spain examinedgenetic variation in the restored populations. Thesepopulations were close to extinction in the 1990s but arestoration programme involving habitat improvements,fishery regulations and a supportive breeding programme,based on native juveniles and returning adults, has beenundertaken since 1995. The study indicated that modernpopulations are very similar genetically to those presentprior to stocking, although the populations are moresimilar today than in the past.

The Connecticut River lost its salmon population about200 years ago due to human activities but a salmon runhas been re-established based mainly on stock from thePenobscot River. The current genetic profile of salmon inthe Connecticut was shown to be very similar to that ofits donor population in the Penobscot, indicating that theeffective number of breeders in both rivers has been largeenough to preserve genetic variability and that no geneticbottlenecks occurred during the restoration programme.The differences that were detected were considered tobe adaptive responses to environmental variation.

A study from the Burrishoole River in Ireland analysedstock and recruitment data for a population receivingvariable, but significant, quantities of naturally spawning,hatchery-origin fish over a thirty-five year period. Theresults suggest that the hatchery fish had a significantdepressive impact on the recipient population of about30% and the author concluded that removal, rather thanaddition, of hatchery fish may be the most effectivestrategy to improve productivity and resilience in wildstocks. In the last eight years, hatchery fish wereeffectively excluded from spawning in the wild and asignificant improvement in freshwater production of smoltswas observed.

Aquaculture-free zones

A presentation from Iceland reported on the rationale forthe establishment of aquaculture-free zones in wildsalmon-producing areas to protect valuable salmon anglingfisheries. Salmon farming is not permitted in bays andfjords with the most valuable salmon rivers and in theareas where it is permitted, the experience gained will be


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used to further evaluate the impacts of salmon farming inIceland.

Behaviour of cultured and wild parr

Studies in the Louvenga River in Russia highlighteddifferences in feeding behaviour between wild andcultured parr. Cultured parr were less able to differentiatefood items from non-food items than wild fish and weremore aggressive. However, wild parr were able tooptimize their feeding conditions by choosing habitats withpreferred sizes of prey, higher densities of food items andcurrent velocities that allowed them to maintain stationand feed effectively.

Domestication effects

The growth, behaviour and physiology of domesticated(fast-growing), non-selected (slow-growing) and hybridstrains of coho salmon and rainbow trout under bothculture and semi-natural rearing conditions werecompared. Under all rearing environments growth wasstrongly correlated with the proportion of domesticgenes. Anti-predator behaviours and hormone profilesshowed similar trends. The study concluded thatknowledge of the genetic changes responsible for alteredgrowth rates in fish is crucial to increasing ability to predictthe consequences of introgression between fast- andslow-growing strains of fish.

2.5 Session 5: Synthesis Session - Challenges and Solutions

This session comprised inputs from a number of sources,including a summary from each of the three plenarysessions and the poster session by the Co-Chairmen (seeAnnexes 2 - 5) and six participants from different interestswere then asked to give their perspectives on theinformation presented during the symposium, i.e. their‘take-home messages’ (see Annex 6). There wereperspectives from two representatives of non-governmentorganizations, two representatives of the salmon farmingindustry and two representatives of administrationsinvolved in the management of salmon farming and wildsalmon. There was also a wide-ranging discussion,including consideration of future research requirements.

There was general agreement in the presentations in thissession that compared to the symposium in Bath in 1997,understanding of the interactions between wild andcultured salmon has increased considerably. Thisinformation had conclusively identified a serious threat tothe wild salmon stocks from escapees, particularly wherethe wild stocks are depressed, and from sea lice. The

salmon farming industry representatives acknowledgedthat it could no longer be claimed that salmon farmingposes no threat to the wild salmon stocks, highlighted theprogress that has been made in addressing impacts andindicated that the industry would continue to addressissues related to interactions with the wild stocks in thefuture. There was recognition that there is a need toavoid a culture of blame and for wild and farmed salmoninterests to work closely together in addressing problems.Generally there has been a significant change in attitudewithin the salmon farming industry since the Bathsymposium with regard to recognition of the impacts theindustry may have on the wild stocks. In Bath, there hadbeen a clear difference in perception between thoserepresenting the salmon farming industry and thoserepresenting wild fish interests. The former had stressedthe economic benefits of the industry and questionedwhether their industry had any significant effects on thewild stocks, while the latter believed that firmer actions bythe industry were required to protect the wild stocks.

Two concerns dominated the session: the need tominimise escapes through improved containmentstrategies and for further improvements to pestmanagement strategies to minimise the impacts of sea lice.While considerable progress has been made in relation toboth issues, the continuing increase in production offarmed salmon means that measures to minimise negativeimpacts of salmon farming must be introduced at a fastertempo than the industry expands.

It was recognised that there was no room forcomplacency despite the progress that has been made,and that there is an urgent need to reduce escapes, forexample through matching technology to site conditions,application of the NASCO/North Atlantic salmon farmingindustry Liaison Group’s containment guidelines, improvedcage design and maintenance, appropriate staff trainingwith regard to operational procedures and increasingawareness of the potential impacts of escapees on wildstocks, continuing research and development into lessvulnerable and more operator-friendly cage systems,improved monitoring systems to determine numbers offarmed salmon in cages, and development of improvedstrains of triploid, or other forms of sterile salmon, with aview to their use by the industry. For sea lice, there is aneed to reduce levels on farmed salmon to as close tozero as possible through use, for example, of areamanagement agreements involving synchronisedtreatments, single year classes and fallowing. In this regardit was recognised that there is a need for an adequate


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suite of anti-lice medications and development of vaccines.Furthermore, additional farm sites may be needed toallow for effective fallowing.

It was recognised that there is a need to further enhancethe dialogue, cooperation and trust that is developingbetween wild and farmed salmon interests and that localand regional cooperation, in addition to regulation, will berequired in future. A solution in which the wild stocks areprotected and the industry can develop in a sustainablemanner, a ‘win-win’ scenario, will require that the evidenceof impacts is accepted and that cooperative and pragmaticways of addressing them are urgently found. The viewwas expressed that the remaining challenges can only beaddressed, and a ‘win-win’ solution found, if all interestspull in the same direction rather than continuing the ‘tug-of-war’ approach that has prevailed in the past. The worstpossible outcome would be that at a subsequentICES/NASCO symposium there are more presentationson mounting evidence of problems rather than reports onthe solutions that have been implemented


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3CONCLUSIONS BYTHE CONVENERS

The trap on the Srahrevagh River, a tributary of the Burrishoole River, used in experiments designed toincrease understanding of wild and cultured salmon interactions.Photograph courtesy of the Marine Institute, Ireland.

3. Conclusions by the Conveners3.1 Introduction

It is clear that since the first symposium in Loen in 1990,scientific understanding of the interactions betweencultured and wild salmon has increased considerably andthe science confirms that cultured salmon can havesignificant negative impacts on the wild stocks. Realprogress has been made in managing interactions butsome significant challenges remain, particularly with regardto further reducing the impacts of escapees and sea lice.These two topics dominated the symposiumpresentations, the discussions and the ‘take-homemessages’ and are, in part, related to the large scale of theindustry. A further positive development since the lastsymposium relates to the extent of cooperation betweenwild and farmed salmon interests and it is clear that thisprocess needs to be further enhanced in future.Furthermore, the industry now acknowledges that itsactivities can have damaging impacts on the wild stocksand we believe that this acceptance provides a basis formaking real progress in finding cooperative solutions tothe remaining challenges.

In developing our conclusions, we have considered thekeynote speeches, the scientific and other informationpresented at the symposium, the summaries made by theChairmen, the ‘take-home messages’ and the discussionsessions. We have also taken into account the findingsfrom the recent Trondheim Workshop (Anon, 2006) andother relevant information.

We have had to evaluate a great deal of material and tomake judgements about it and about how much weight togive it in coming to conclusions. We want to make it clearthat to do this inevitably involves a great deal of personaljudgement. The reader will be aware that this is the casein coming to many professional or other judgements. Justas two different juries might well have come to differentverdicts after hearing evidence from the same trial, twodifferent conveners might have come to somewhatdifferent conclusions from this symposium. However, weare comforted that in coming to our conclusions, therewas a degree of unanimity at this meeting that was notpresent at the two earlier symposia, which helps us greatly.We want to reassure the readers of this report that wehave tried hard to be objective.

We also need to make it clear that although NASCO andICES co-convened, and other organizations sponsored, andsupported, the Bergen symposium, the views expressed

here are entirely those of the two Conveners.

We have come to a number of conclusions. It should benoted, however, that while the title of the symposiumreferred to interactions between wild and cultured salmonand other diadromous fish species, the vast majority ofpapers concerned interactions between wild and farmedAtlantic salmon and our conclusions therefore relateprincipally to these interactions and their management.

3.2 The Salmon Farming Industry

A major change, and a most welcome one, since the lastICES/NASCO symposium in Bath in 1997, is that thesalmon farming industry, certainly those representativespresent in Bergen, now fully accept that their industry canhave damaging impacts on the wild stocks. We very muchwelcome this because it is a prerequisite to cooperativeaction. We realize that, for various reasons, this has notbeen easy for them to accept, but this acceptance canhave major dividends for cooperation to mutual benefit inthe future. In Bath and before, there had been a climateof blame, public accusation and counter-accusation. Today,we feel that the climate has greatly improved, as wasdemonstrated at the symposium.

As concrete evidence, we look not only at statementsmade by representatives of the industry at the Bergensymposium, but at the newly energized NASCO/NorthAtlantic salmon farming industry Liaison Group which, forthe first time, held a joint meeting earlier in 2005, theTrondheim Workshop, which not only discussed anddebated some controversial issues (such as use of sterilefish in aquaculture) but sought new ways to cooperate(Anon, 2006). The goodwill and frankness thatcharacterized both that meeting and the Bergensymposium should encourage us all to build on thecooperation that is developing.

It will be evident from this report that we, the Conveners,believe that it is vital that actions be taken to protect andconserve the integrity of the wild stocks. But we wouldargue that it is clearly very much in the interests of ourcolleagues in industry, too. It protects their ‘seed corn’,their future, it protects them from bad publicity and intoday’s climate we expect that that aspect is vital for theirfuture marketing, sales and economic success.

Both Conveners have been involved in these issues ofinteractions between farmed and wild salmon for manyyears but, for the first time, we feel encouraged by a newatmosphere of cooperation, frankness and the will tosucceed. We hope that this will characterize the


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consideration of our conclusions from the Bergensymposium. We do not underestimate the difficulties ofimplementing some of our conclusions, but we mustemphasize the potentially severe damage to the wildstocks, and consequently the costs to society, of not doingso.

3.3 Disease and Parasite Interactions and their Management

There has been considerable progress in addressingdisease and parasite problems in aquaculture through, forexample, improved husbandry and use of vaccines. Therehas also been progress in developing managementstrategies to reduce the levels of sea lice on farms andthereby reduce transmission to the wild. While sea troutappear to be particularly badly affected there is evidenceof impacts on wild salmon stocks as well. In somesituations wild salmonid populations have suffered stockcollapses that have been linked to sea lice infestations.Such stock collapses have implications for the diversity ofthe wild stocks (see section 3.4). It is clear that actionssuch as coordinated lice treatments, use of singlegenerations and fallowing through area managementinitiatives are having benefits in protecting the wild stocksand that the cooperation between wild and farmedsalmon interests on these initiatives is a positivedevelopment. However, there may still be problems forwild stocks from sea lice, perhaps more so during thesecond year of the farm production cycle. Thesemanagement strategies may be voluntary but in somesituations they may need to be incorporated inregulations. Successful area management depends oncommitment from all partners, open dialogue,transparency and input from all interested parties.

Significant challenges remain in addressing sea lice issues,not least the need for the industry to be allocatedadditional sites to facilitate on-growing of singlegenerations, and the limited number of treatmentsapproved for sea lice control. While effective treatmentsare available, not all are licensed for use in aquaculture inall countries and we urge the regulatory authorities tomake these available as quickly as possible whereenvironmentally acceptable. Development of resistance tothe available treatments in the future would have seriousimplications for both wild and farmed salmon interests.Development of a vaccine against sea lice would be amajor step forward. Alternative approaches, such as theuse of wrasse in the cages to clean salmon of sea lice,might offer benefits.

The eradication of the parasite G. salaris from infectedrivers and prevention of its further spread are essential. InNorway, the parasite was spread by stocking following itsintroduction from the Baltic. Risk analysis suggests thatmovements of live fish, particularly rainbow trout, are themost likely source of spread among other countries. Thisis a difficult area since it raises issues associated withinternational trade agreements but it is essential thatappropriate safeguards are in place to control suchmovements in a manner that does not jeopardize the wildstocks. It is also important that the two chemicaltreatments presently in use in Norway to eradicate theparasite, rotenone and acidified aluminium sulphate, areavailable for use in future. NASCO’s North-East AtlanticCommission has developed recommendations in relationto G. salaris (NASCO, 2004; 2006b) and we believe that itis important that these recommendations areimplemented urgently.

3.4 Genetic and Ecological Interactions and their Management

Although there has been progress in reducing theproportion of farmed fish that escape to the wild, thegrowth in production by the industry means that thenumber of fish escaping is still large relative to the wildstocks. There is no doubt that a proportion of escapeesenter rivers and interbreed with the wild stocks. In somecases, they make up very high percentages of spawningstocks and genetic changes in some wild populations havebeen detected. To put it bluntly, this means that in the last30 years a large-scale, uncontrolled genetic experiment,which we believe poses the risk of irreversible changes tothe wild stocks, has been undertaken. It is still continuing.In doing so, in the North Atlantic we are running the riskof changing local adaptations that have taken centuries ormore to develop by allowing fertile farmed salmon, whichhave been selected for traits valuable to aquaculture, tointerbreed with the wild stocks that have evolved theirown characteristics over millennia.

Since the symposium we are aware of recent advice fromICES to NASCO regarding the genetic impacts of farmedAtlantic salmon on the wild populations (ICES, 2006b). Inthis advice ICES indicates that very large numbers offarmed salmon escape annually relative to wild salmonabundance; a substantial body of useful quantitative dataon genetic impacts of farmed salmon on wild stocks hasbeen collected; gene flow from farmed to wild salmon willreduce the natural inter-population heterogeneity found inthe wild Atlantic salmon, therefore reducing the adaptive


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potential of the species; and experimental studies confirmthat escaped farmed salmon can have major negativeimpacts on wild salmon populations.

In Bergen, information was presented confirming thatgenetic changes have been observed in some wildpopulations exposed to escapees but not in others,suggesting that the impacts are influenced by the numbersof farmed fish intruding, their reproductive success (whichmay be related to the time they have spent in the wild)and the abundance of the wild fish population in the river.The results of a model that simulated a 20% fixed annualintrusion rate of farmed escapees suggest that within tensalmon generations there will be substantial changes in thewild population. These changes may be irreversible. Insome Norwegian rivers the proportion of escapeesalready greatly exceeds 20%. Low intrusion scenariossuggest that farmed offspring are unlikely to becomeestablished in a population whereas high intrusionscenarios suggest that the populations eventually becomemixtures of hybrid and farmed descendants. Recovery ofwild populations is not likely under all circumstances evenafter many decades without further intrusions. Thesefindings are extremely worrying to us.

We recognize that these models may be over-simplifiedand merit further development. Nevertheless, theimplications of permanently and irreversibly altering aNorth Atlantic salmon stock structure that has probablypersisted for millennia, with consequences for the viabilityand productivity of these stocks, can hardly be overstated.

The new information both from the symposium and fromICES can only lead to the conclusion that urgent action isrequired to eliminate these interactions. The hugedisparity in numbers of wild and farmed fish means that ifthe problem is to be dealt with effectively, either physicalcontainment would have to improve so much as to beeffectively 100%, or biological containment (use of sterilefish) in aquaculture would have to be implemented.

We are well aware of the costs and difficulties associatedwith both of these options but what are the costs ofdestroying the genetic integrity of the wild stocks? Couldthe salmon farming industry itself suffer catastrophically atsome future time if the genetic diversity of the specieswas lost? Would consumers be willing to pay more forfarmed salmon that were reared in a manner thatsafeguarded the wild stocks (as with dolphin-friendlytuna)? We urge that this issue be addressed with a newurgency. There is no time to lose and it should not be aninsuperable problem to keep 100% of farmed fish in cages

or to introduce triploid fish. The technology for the latteris well established though the husbandry will need to beimproved. But even if the decision was taken today to usetriploid salmon, it would take about ten years before theycould be available on a commercial scale and considerablylonger if selection for improved performance is to beachieved. We urge that the technology and the husbandryof sterile fish be further assessed so that it might beintroduced later. It seems to be the one approach thatcan deliver 100% containment. In the interim, however,improved physical containment measures should beimplemented in both marine and fresh waters, such asgreatly improved cage design, screening, etc., andelimination of ‘trickle losses’ (for example during handling,net changes, fish transfers, etc.), and consideration shouldbe given to establishing more protection areas for wildfish. The NASCO/North Atlantic salmon farming industryLiaison Group’s containment guidelines should, therefore,be seen as a minimum standard for physical containmentthat need to be implemented widely and reviewed as totheir continuing appropriateness given the latestinformation.

It is not just intrusions from accidental escapes of farmedfish that pose a risk. There are risks, we believe, fromdeliberate stocking of salmon rivers. It is certainly not thecase that stocking is always beneficial; it can do harm. Thegoals and rationale for such stocking need to be verycarefully evaluated before such action proceeds, and weurge those involved to follow the stocking guidelinesdeveloped by NASCO (NASCO, 2006a).

The conclusions about genetic change above are, webelieve, the most important ones emerging from thesymposium. There are also some subsidiary issues:

• storms were identified as a major source of escapes in‘catastrophic’ losses and since most climate-change scenarios involve stormier weather than at present, wedo not see present containment arrangements as adequate;

• when fish escape they may disperse very quickly from the site of release, moving with the currents, and their fate is probably very variable. Thus we believe that in many situations there will be difficulties in recapturing escapees immediately, and such efforts would require contingency plans to be in place detailing the gear to be used and other arrangements. Other approaches might involve recapture efforts targeting escapees which may enter rivers later than wild fish;


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• monitoring programmes for escapees should ideally bebased on scientific sampling programmes independent of the fisheries for wild salmon and targeted on areas in proximity to the fish farming activity;

• the number of escapees is significantly under-reported,not necessarily as a result of deliberate intent but, for example, because of ‘trickle losses’. There is a need for improved reporting procedures and methods for assessing the number of fish in cages. It is important that systems are in place that provide early warning of escapes and that information is provided by farmers on the number of fish escaping, the date and time of escape, the life stage and size of the escapees, their health status, and, if available, information on their genotype.

3.5 Research Recommendations

There has been significant progress in our understandingof interactions and their management since the lastsymposium in 1997. However, there is a need for furtherresearch and development if the interactions betweenwild and farmed fish are to be managed successfully, andwe have listed the main topic areas here:

• development of improved cage technology to ensure containment of farmed fish;

• development of methods to monitor the stock of farmed salmon in cages and to detect escape events atan early stage;

• improvements to the performance of sterile (all-femaletriploid) fish for use in aquaculture and development of alternative methods to produce sterile fish;

• development of domesticated strains of farmed fish with low survival in nature;

• development of methods to identify farmed salmon in nature and trace them back to strain or farm of origin;

• improvements to understanding of the performance (migration, dispersal and survival) and life history strategies of farmed salmon escaping at different sites,times and life stages;

• development of models to predict the fate of escaped farmed salmon;

• further development of methods to control sea lice in fish farms and to minimise resistance to therapeutants;

• further development of models to predict dispersal and survival of sea lice larvae in nature;

• introduction of improved, standardised scientific monitoring of farmed salmon in wild salmon populations;

• development of improved approaches to recapturing escaped farmed salmon;

• further development and refinement of models to predict genetic and ecological impacts of farmed salmon on wild fish; and

• assessment of the socio-economic effects of escaped farmed salmon.

However, under the Precautionary Approach the absenceof adequate scientific information should not be used as areason for postponing or failing to take conservation andmanagement measures.

3.6 Final Thoughts

When, nine years later, we read the conclusions from theBath symposium we find that they are still mostly valid butwith an added urgency. The interactions between farmedand wild salmon can be damaging and need to beeliminated, not just reduced. There are risks not only fromfarmed fish but from inappropriate stocking practices,which also need to be addressed.

NASCO, all of its Parties and relevant jurisdictions haveadopted the Precautionary Approach and two centralplanks of this approach are that: the absence of adequatescientific information should not be used as a reason forpostponing or failing to take conservation andmanagement measures; and that priority should be givento conserving the productive capacity of the resourcewhere the likely impact of resource use is uncertain. Weconsider that the matter of escapees and sea lice must beseen as urgent because of the risks of irreversible changesin the wild stocks.

We believe that progress in addressing the sea liceproblem is being made. Progress can continue to bemade by concerted action and widespread use of bestpractice, but it is clear that challenges remain if the wildstocks are to be protected, particularly with regard to seatrout populations. The prospect of resistance developingto the treatments available is also a real concern for bothwild and farmed salmon interests. Much more progress inimproving containment is, however, urgently neededbecause continuing escapes of fertile farmed salmon areputting at risk the very stock structure and diversity of thewild North Atlantic salmon. Farmed salmon must bemuch more effectively contained. It is odd, to say the


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least, that the escape into the marine environment of hugenumbers of farmed fish (millions in some years) isaccepted as ‘normal’.

Farming of salmon is a very competitive sectorinternationally. Nevertheless, we can only repeat whatwas reported from Bath in 1997, that we believe that newapproaches and attitudes to escapees are required andthat they should apply to all areas of the North Atlanticso that, internationally, salmon farming operates on aneven-handed basis. There will always be the response thatone major producer, Chile, will not need such stringentpractices because it has no wild stocks to conserve andthat this will put other producers at a competitiveadvantage. That may be so but it is illogical, in our view, toallow damage to North Atlantic stocks because acompetitor operates without this concern. We might aswell argue that we will not clean up our air pollution byrequiring our car industries to have catalytic converters,because it is not required in other parts of the world.

Quite apart from NASCO’s obligation to protect wildstocks, there are requirements under the Convention onBiological Diversity to conserve genetic diversity bothwithin and among species. If no action is taken now, and ifthe views of the many scientists and experts at thissymposium, and the two preceding symposia, are correct,we risk the loss of the diversity of local adaptations in thewild stocks of salmon in the North Atlantic. This may wellhave serious consequences for their fitness, productivityand their ability to survive environmental change.


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REFERENCES

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4. ReferencesAnon. 2006.Wild and Farmed Salmon - Working Together.

Report of a one-day workshop organised by the NASCO/North Atlantic salmon farming industry Liaison Group. North Atlantic Salmon Conservation Organization (NASCO),Edinburgh, Scotland, UK. 86pp.

Hansen, L. P., Håstein,T., Naevdal, G., Saunders, R. L., and Thorpe, J. E. (Eds). 1991. Interactions between cultured and wild Atlantic salmon. Proceedings of a symposium hosted by the Directorate for Nature Management and Norwegian Institute for Nature Research, held in the Hotel Alexandria,Loen, Norway, 23 - 26 April 1990. Aquaculture,98: 1-324.

Hutchinson, P. (Ed). 1997. Interactions between salmon culture and wild stocks of Atlantic salmon: the scientific and management issues. ICES Journal of Marine Science, 54: 963-1225.

Hutchinson, P. (Ed). 2006. Interactions between aquaculture and wild stocks of Atlantic salmon and other diadromous fish species: science and management, challenges and solutions. ICES Journal of Marine Science, 63: 1159-1371.

ICES. 2006a. Report of the Working Group on North Atlantic Salmon (WGNAS), 4 -13 April 2006, ICES Headquarters. ICES CM 2006/ACFM:23. 254pp.

ICES. 2006b. Scientific Advice from ICES - Assessing Genetic Effects. Supplementary report to the North Atlantic Salmon Conservation Organization (NASCO), Edinburgh, Scotland, UK. Council document CNL(06)41. 6 pp.

NASCO. 2004. ‘Road Map’ for Taking Forward the Recommendations from the Workshop on Gyrodactylus salaris in the Commission Area. NorthAtlantic Salmon Conservation Organization (NASCO), Edinburgh, Scotland, UK. North-East Atlantic Commission document NEA(04)13. 8 pp.

NASCO. 2006a. Resolution by the Parties to the Convention for the Conservation of Salmon in the North Atlantic Ocean to Minimize Impacts from Aquaculture, Introductions and Transfers, and Transgenics on the Wild Salmon Stocks, the Williamsburg Resolution (Adopted at the TwentiethAnnual Meeting of NASCO in June 2003 and amended at the Twenty-First Annual

Meeting of NASCO in June 2004, and at the Twenty-Third Annual Meeting of NASCO in June 2006). North Atlantic Salmon Conservation Organization (NASCO), Edinburgh, Scotland, UK.Council document CNL(06)48. 44 pp.

NASCO. 2006b. Report of the Working Group on Gyrodactylus salaris in the North-East Atlantic Commission Area. North Atlantic Salmon Conservation Organization (NASCO), Edinburgh,Scotland, UK. North-East Atlantic Commission document NEA(06)3. 48 pp.

Youngson, A. F., Hansen, L. P. and Windsor, M. L. 1998.Interactions between salmon culture and wild stocks of Atlantic salmon: the scientific and management issues. Report by the Conveners of a symposium organised by ICES and NASCO, held atBath, England, UK during 18 - 22 April 1997.Norwegian Institute for Nature Research (NINA),Trondheim, Norway. ISBN 82-426-0884-9.


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ANNEX 1Abstracts

The acidified River Mandal, Norway where a stock rebuilding programme involving liming and stockingis being undertaken.


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Annex 1: AbstractsNote:These abstracts are those submitted prior to thesymposium.

Keynote PresentationsWild Atlantic salmon - so valuable, sovulnerablePat O’Reilly

After briefly surveying the environmental, social andeconomic benefits of healthy wild salmon stocks tocommunities in countries bordering the North Atlantic, inthis keynote address the author also highlights the Atlanticsalmon’s iconic significance worldwide. There follows abrief review of past and present pressures on salmonstocks not only via direct exploitation but also via damageto their environment and measures already taken orunderway to reduce impacts via the air, land and freshwater. Finally, the presenter focuses on the marineenvironment and proposes aspects which, withinternational cooperation and partnership working, needto be urgently addressed in order to forge a sustainablefuture for the salmon farming industry and to conservefor future generations healthy, abundant wild salmonstocks.

A global review of the salmon farmingindustry and developments with regard tosustainabilityHelge Midttun

Farming of Atlantic salmon is a young industry. It startedin Norway in the 1960s and has since spread to variouscorners of the world. In 2004, production of Atlanticsalmon made up close to 80% of the global production ofsalmonids, which was around 1.5 million tonnes. Thelargest salmon-producing countries today are Norway,Chile, Scotland and Canada. In the Northern hemisphere,Norway is the biggest producer of Atlantic salmon, andthe salmon industry has become an important means ofincome for many communities along the long coastline.Norway has clean waters and environmental conditionsthat are well suited for building a viable and sustainableaquaculture industry. Like any other industrialised foodproduction system, salmon farming impacts theenvironment, and the salmon producers must accept thatthey will be subject to rigorous evaluation of theenvironmental impact of their activities. Fortunately,through focus and dedication from all stakeholders in the

industry, and in close collaboration with the authorities,many of the environmental problems associated with thesalmon industry have been substantially reduced as theindustry has matured. Improvements have becomenoticeable in areas such as fish health, feed resourcesmanagement, net pen technology, etc. Through continuedefforts on R&D and technology development the industryis expected to advance even further in the future. Thesalmon industry has evolved rapidly, and in order tocontinue to grow is dependent on a clean environment.Going forward, maintaining high environmental standardsand securing a fully traceable and sustainable chain ofproduction will be a prerequisite for maintainingconsumer trust in salmon.

An overview of the status and managementof wild Atlantic salmon (Salmo salar L.)Walter W Crozier

Atlantic salmon occur naturally in over 2,000 rivers fromaround latitude 43oN to latitude 70oN along the coastsbordering the North Atlantic Ocean. Catch trends reflectvariously the evolution of fishery types, the abundance ofsalmon and also the impact of management measures.Since the adoption in 1983 of the Convention for theConservation of Salmon in the North Atlantic Ocean, thedistant-water fisheries at West Greenland and Faroes havebeen regulated by the North Atlantic SalmonConservation Organization through internationallynegotiated quotas. In the 1980s, reducing stockabundance began to seriously impact catches and, morerecently, catches have declined further as a result ofmanagement measures introduced to conserve stocks.The latter have included various compensatory non-fishingschemes in the distant-water fisheries, progressivemoratoria, buyouts and closures of commercialhomewater salmon fisheries in some countries, togetherwith restrictions on rod fisheries in many rivers. Wildsalmon have increasingly come under a wide range ofpressures, including habitat loss and degradation, pollution,predation, climate change effects and possible interactionsbetween wild and reared salmon and, as an overall result,stock status has declined in many parts of the naturalrange. The most recent assessment by the InternationalCouncil for the Exploration of the Sea shows that theNorth American and European stock complexes areoutside precautionary limits. Management advice hasevolved in response to the requirements of thePrecautionary Approach, with conservation limit referencepoints having been defined and catch advice increasingly


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being framed in terms of probability of achieving pre-agreed management objectives. With many salmon stocksaround the North Atlantic presently outsideprecautionary limits, and in some cases threatened orendangered, managers are beginning to place emphasis onseeking catch advice in terms of rebuilding objectives forparticular stocks or groups of stocks.

Cultured Atlantic salmon in nature: reviewof ecology and interactions with wild fishBror Jonsson and Nina Jonsson

Hatchery-raised Atlantic salmon released in naturecompete with wild fish for food, space and breedingpartners. Their competitive ability differs from that of wildfish owing to morphological, physiological, ecological andbehavioural changes which occur in hatcheries.The changeis partly phenotypic, partly genetic. The faster growth rateof hatchery juveniles influences age and size at smoltingand maturity, reproductive output and longevity. Fast-growing parr tend to smolt younger, produce more butsmaller eggs, and attain maturity and die younger. Juvenilelearning influences a number of behavioural traits, anddifferences in early experience appear to affect feedingand spawning success, migratory behaviour and homingability. The genetic change is chiefly due to naturalselection in hatcheries with differential mortality amonggenotypes, and brood stock selection based onproduction traits such as large adult body mass and fastgrowth rate. Due to higher aggression, experimentalevidence has revealed that hatchery parr often dominatewild parr, but hatchery parr can be subordinate if smaller,when they co-occur in fast-flowing water and when wildsmolts have prior residence. During spawning, the fitnessof wild salmon is higher than that of hatchery-rearedconspecifics. Hatchery males do poorly in intra-sexualcompetition, courting and spawning, and hatchery femaleshave higher egg retention, construct fewer nests, and areless efficient in covering of the eggs in the bottomsubstratum. In rivers, early survival of hatchery offspring isreduced compared with their wild counterparts.Experimentally, it has been found that the life-timereproductive success of farmed fish is only 1/6 of that ofsimilar-sized wild salmon. As a result of ecologicalinteractions, hatchery fish may partly displace, increase themortality and decrease the growth rate, adult size,reproductive output, biomass and production of wildconspecifics through density-dependent mechanisms.

Genetic and Ecological Interactions andTheir Management

Genetic and ecological interactions betweenwild and cultured diadromous fishKjetil Hindar, Ian A Fleming, Phillip McGinnity and Ola Diserud

Cultured salmonids are released in large numbers, eitherintentionally or accidentally, and make up significantproportions of salmonid populations in fresh and saltwater. This causes considerable concern, becauseinteractions between cultured fish and wild fish canreduce the fitness and productivity of wild populations.The interactions must be understood both within thespecies’ range and outside it, as salmon aquaculture is aworldwide enterprise. This paper reviews genetic andecological interactions between wild and cultureddiadromous fish, focusing on the effects of farm Atlanticsalmon (Salmo salar) on wild salmon. Farm salmon havebeen under artificial selection for growth and othereconomically important traits for 30 years, and aregenetically different from their origin at the molecular andquantitative genetic level. Escaped farm salmon spawn inthe wild with limited success. Their offspring outgrowthose of wild origin, but appear to suffer higher mortality.Crosses between farm and wild salmon showintermediate performance. Whole-river experiments inIreland and Norway show that the lifetime success of farmsalmon was reduced relative to wild salmon. The overallproductivity also appeared depressed. Based on thesefindings, we make model predictions about the future ofwild salmonid populations.

Interactions between salmon farming andmarine coastal ecosystems in the south-eastPacificAlejandro H Buschmann, Verónica A Riquelme, María CHernández-González, Daniel Varela, Jaime Jiménez, Luis AHenríquez, Pedro A Vergara, Ricardo Guiñez and Luis Filún

Salmon aquaculture exportation in Chile reached 311,000tons in 2004, making it the second-largest producer offarmed salmon in the world behind Norway. Because ofthis, the industry is now considered as consolidated butwith further potential expansion. In order to keep ongrowing, the salmon industry must expand its activitiesfurther south and thus reach pristine areas with littlehuman activity so far, resulting in increasing calls forconservation actions. Nevertheless, the environmentaleffects of salmon cultivation in southern Chile remain


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largely unknown. The impact of this industry before 1996has been reviewed, but evidence at that time did notsuggest significant effects. However, after almost 10 yearsof intensive growth, current evidence suggests that someeffects on the sea bed in licensed aquaculture areas areassociated with significant loss of benthic biodiversity inaddition to changes in the physico-chemical properties oflocal sediments. Another main aspect is related to theinduction of harmful algal blooms (HABs) through theinput of nitrogen into the water from fish culture facilities.A field study carried out using the beyond BACI samplingmethodology described by Underwood (1994) suggeststhat the presence of salmon pens significantly increasesthe density of dinoflagellates, in pulses however. Salmonescapees are another public concern, with data suggestingthat they prey on native species, although the lifeexpectancy of farmed salmon in the wild appears to berather low. Marine birds are also affected by theinstallation of salmon farms, where the particularabundance of omnivorous, diving and carrion-feeding birdsincreases from three to five times in areas with salmonaquaculture installations compared to control areaswithout them. Chile urgently requires an ecosystemapproach in order to fully understand all the effects ofaquaculture activities on its southern coastal ecosystems.

Past, present and future of geneticimprovement in salmon farmingOdd Magne Rødseth and Arne Storset

Historically, fish culture can be traced back to 475 B.C. inChina. In Europe, management of common carp wascommon in monasteries during the Middle Ages. Theintroduction into Europe of American salmonids, rainbowtrout and brook trout, opened the ‘modern’ era of fishfarming. A fourth period came with the development ofdry pellet feeds in the 1960s. The fifth period startedwith the development of the farming of Atlantic salmon insea cages in the 1970s. This marked the starting point oflarge-scale farming of Atlantic salmon which rapidly spreadto Scotland, Ireland, the Faroe Islands, North America andChile, the latter being the fastest-growing player in themarket. The sole effect of domestication of wild fishimproves production performance in several respects.Although data are scarce, decrease of mortality andincrease in growth rate due to domestication are welldemonstrated for species like common carp, rainbowtrout and Atlantic salmon. To increase the productionperformance considerably, the stocks must be improvedby means of selective breeding. Selection is the process

that determines which fish become parents. There aredifferent modes of selection, the most important of whichbeing: (i) selecting individual fish out of the entirepopulation (mass selection), (ii) selecting particular familiesout of the population (family selection). The number ofparents selected (selection intensity) must attempt tobalance the rate of genetic improvement needed withmaintenance of suitable genetic variation. To improve apopulation, only the fish with the best genes should beselected as parents. A breeding value is a quantitativecalculation of the value of a fish as a genetic parent, and isa measure of the potential performance of its offspring.Therefore the ‘best’ fish are those with the best breedingvalues. The definition of ‘best’ depends on the economicimportance of traits and their underlying genetics.Currently, less than 5% of the fish material stocked foraquaculture originates from selection programmes. Mostof the genetic improvement in fish is based on massselection without any pedigree information (97% ofaquaculture). Advances in selection methodologiesdeveloped for livestock animals have been transferred tofish for application in family breeding programmes(Atlantic salmon, rainbow trout, tilapia, Arctic char, shrimp).A family selection programme for Atlantic salmon wasinitiated by AKVAFORSK in the early 1970s. The basepopulations consisted of wild salmon caught in some 40Norwegian salmon rivers. This is the most long-lasting andcomprehensive breeding programme in fish and has, sincethe mid-1980s, been run by Aqua Gen AS. The presentsalmon generation is the result of the eighth selection.Mass selection can only be used to improve traits that arerecorded on the breeding candidates while they are stillalive (e.g. growth, shape, colour, low percentage of grilse),and it is not efficient to improve discrete and lowlyheritable traits such as survival rate. To improve carcassand meat quality traits family breeding must be employed- the same with resistance to specific pathogens andparasites. In Aqua Gen’s breeding programme resistanceagainst one bacterial and two viral diseases are included.Research and requirements from the fish farming industryand customers will most probably bring forth newbreeding technologies and focus areas in future fishbreeding: Molecular methods: DNA fingerprinting isalready in use in parentage assignment in family breedingprogrammes. Marker-assisted selection and genomicselection are novel technologies that in the future willsupplement traditional breeding based on quantitativegenetics and make the selection more precise and cost-efficient. Transgenic technology seems to be efficient toimprove growth in wild fish, but seems to be less efficient


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in domesticated populations. The development oftransgenic fish is in progress in many countries in Asia andLatin America. In Europe and Canada, production oftransgenic Atlantic salmon is discouraged (TheWilliamsburg Resolution, NASCO June 2003). Ability toconsume vegetal ingredients and improvement of feedconversion and feed utilization: Atlantic salmon and manyother fish species are carnivorous. Fish proteins can bereplaced by other sources, but they are highly dependenton fish oils. Selective breeding to obtain a fish that canutilize vegetal oils to a greater degree and be more feed-efficient will make aquaculture more sustainable withregard to marine feed resources. Maintain animal integrityand functional traits and animal welfare: Effects of selectionmust always be monitored as part of a selectionprogramme in order to detect any production disordersthat may arise. Selective breeding to bring forth a morerobust fish with high survival and good productionperformance under aquaculture conditions will beincreasingly important in future breeding programmes.Preservation of wild stocks: Fish can escape and breed withtheir wild conspecifics. Use of sterile triploid fish isadvocated as a tool to decrease genetic interactionbetween domesticated and wild populations. Reluctancein the industry due to negative impacts on productionperformance, and public perception of triploid fish asrepresenting unethical production, are factors that willhamper use of triploid fish in Atlantic salmon farming.Further genetic selection and domestication will probablyreduce the reproductive fitness of escapees incompetition with wild conspecifics, thus reducing theimpact of genetic interaction between domesticated andwild populations.

The causes and scale of escapes fromsalmon farmingAina Valland

In Norway, the Directorate of Fisheries has collected andpresented statistics on the scale and causes of escapesfrom salmon farming for more than the last 12 years.Through regulations the fish farmers are required toreport all escape incidents and their causes to theauthorities. The statistics are based on these reports andreports to the insurance companies. The figurespresented are based on these statistics. Escapees fromsalmon farming have varied from 200,000 to nearly500,000 each year in the last 12 years. The industry fullyaccepts that these numbers are too high, and the aim is toachieve a level of escapes that is as close to zero as

practicable. Most Norwegian farmers do achieve zeroescapees within their own company, thus only 2-3 perthousand farmed salmon escape. There are variouscauses of escapes. The Directorate of Fisheries dividesthese causes into the following categories: technicaldeficiencies, towing, handling, running over by boat, boatpropellers, predators, floating objects and technicaldeficiencies in smolt production. Working towards theaim of achieving a level of escapes that is as close to zeroas practicable, the Norwegian salmon farming producershave a ‘National Action Plan to prevent escapees’. Theplan is in active use and is continually revised, and itfocuses on preventive measures regarding all causes ofescape.

The escape of juvenile salmon fromhatcheries into freshwater streams in NewBrunswickJonathan W Carr and Fred G Whoriskey

The escape of juvenile Atlantic salmon from freshwaterhatcheries may be a major route for interactions betweenwild and farmed fish; however, the scale of this problemhas not been substantially examined. We monitoredtemporal abundance of escaped hatchery salmon at fixedsites: over several years, and surveyed more than 90% ofthe salmonid hatcheries in New Brunswick in 2004.Escaped fish were recorded at 61% of the hatcheriessituated near freshwater streams. Numbers varied persite; however, escaped fish were found every year at thefixed sites. In some rivers, juvenile escapees outnumberedwild salmon. A sample of escaped farmed salmon wasgenetically screened for the presence of European alleles.The use of European salmon strains has been prohibitedon the east coast of Canada and United States for severalyears. For the first time in eastern Canada, varying levelsof European ancestry were detected in escaped farmedsalmon. These results highlight the need for theimplementation of a containment strategy for freshwaterhatcheries and a genetic screening programme of farmedsalmon to reduce escapes and to stop the introgression ofEuropean genes into severely depressed wild Atlanticsalmon populations in the Bay of Fundy region.

Sonic tracking of experimentally releasedfarmed Atlantic salmon in the Cobscook Bayregion, MaineFred G Whoriskey, Paul Brooking and Gino Doucette

Farmed Atlantic salmon (Salmo salar) (N = 273) weresurgically implanted with sonic tags (pingers), and


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experimentally ‘escaped’ from their cage site during winter2003 and spring 2004. Experimental releases occurredduring either the day or night, on rising and falling tides.Cobscook Bay has a large tide range and fast tidalcurrents. Moored receivers were positioned to follow themovements of these fish in the Bay and surroundinginshore areas, up to the point that they dispersed fromthe coastal zone to open water in the Bay of Fundy.Additional receivers and counting facilities placed in 40rivers draining to the Bay of Fundy let us determinewhether surviving escapees strayed into them, especiallyduring spawning season. In both seasons, escapeesgenerally dispersed rapidly away from their cage sites.Heavy seal predation apparently rapidly killed manyescapees in spring, but not winter. Course tracks of thefish indicate a combination of active swimming and driftwith prevailing tidal currents. None of the escapees weredetected entering rivers in the region where they couldinteract with spawning of endangered wild populations ofAtlantic salmon.

Migration and survival of farmed Atlanticsalmon (Salmo salar L.) released from twoNorwegian fish farmsLars P Hansen

Salmon escape from fish farms, and high numbers ofescaped farmed salmon have been reported fromNorwegian fisheries and spawning populations, as well asin oceanic areas north of the Faroe Islands. Many salmonescape from fish farms in the autumn and winter, and it istherefore of interest to study the migratory pattern andsurvival to sexual maturity of farmed fish escaping at thistime of the year. The purpose of the present study was toassess migration and survival of large farmed salmonescaping from fish farms at different times in the autumnand winter. Farmed salmon were individually tagged withexternal tags and released from two fish farms, one insouth Norway and the other in north Norway. Salmonreleased in the autumn one year before attaining sexualmaturity appeared to survive poorly to sexual maturation,whereas salmon escaping later in winter showed highersurvival. The escaped salmon tended to move with thecurrent, and did not appear to have a homing instinct.Based on results from the tagging experiments, directionand speed of ocean currents, and from availableinformation of the abundance of fish farm escapees insalmon fisheries and stocks in several countries innortheast Europe, two alternative hypotheses areproposed: (1): Salmon that escape early in the autumn the

year before they become sexually mature are transportedwith the currents to arctic areas and subsequently do notsurvive the winter. (2): Large salmon escaping from fishfarms in Ireland, Scotland, the Faroe Islands and Norway inthe winter and spring move with the current and mayenter homewater fisheries and spawning populations faraway from the site of escape, the following summer andautumn, when they become sexually mature.

The incidence of escaped farmed salmon inrelation to the extent of fish farmingactivityPeder Fiske, Roar A Lund and Lars Petter Hansen

In Norway, there have been restrictions on salmonfarming in several fjords to reduce the potential negativeimpact from farming on important stocks of wild Atlanticsalmon. This practice is now being revised, and hasresulted in the establishment of ‘National salmon riversand fjords’ with similar restrictions on salmon farming.There is limited knowledge on the incidence of escapedfarmed salmon in fisheries and brood stocks related tothe extent of fish farming in nearby areas. Suchknowledge will be of significant importance whenassessing if measures such as ‘National salmon fjords’ arelikely to reduce the number of farmed salmon in nearbyrivers. A pilot study published in 1994 concluded that fishfarm escapees occur in fisheries and brood stocks moreas a result of a number of small escapement episodesrather than by large single escapements. This wasdemonstrated by a positive correlation between theproportion of escaped farmed salmon in marine salmonfisheries and brood stocks in relation to the density ofrearing units and the number of smolts released into seapens in the different geographical regions considered. Thiswork was based on results from the two first years (1989and 1990) of the nationwide surveillance programme ofthe salmon stocks in Norway. The present study has thesame scope, but is based on data from 16 years ofsurveillance (1989-2004). Norway is divided into differentregions, and we analyse the incidence of escaped farmedsalmon in the fisheries in relation to the intensity ofsalmon farming in the different regions. Our resultssuggest a positive correlation between the intensity ofsalmon farming, and the incidence of escaped farmedsalmon in the rivers in the nearby area.


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The development and results of programmesto monitor the incidence of farm-originAtlantic salmon (Salmo salar L.) in riversand fisheries of the British IslesAlan Walker, Malcolm C M Beveridge,Walter Crozier, NiallO’Maoileidigh and Nigel Milner

An inevitable consequence of the development of theAtlantic salmon (Salmo salar L.) mariculture industry in UKand Irish coastal waters over the last three decades hasbeen the loss of farm-origin fish to the wild, theiroccurrence in inshore waters and rivers, and theirexploitation by commercial and recreational fisheries.Since 1984, the International Council for the Explorationof the Sea (ICES) has reported the results of national andother programmes to quantify the occurrence of escapedfarmed salmon in international waters, homewaterfisheries and in river stocks, and more recently hasexamined methodologies to improve knowledge on thedistribution and movements of escapees. In this paper wereport on the development of programmes to quantifythe spatial and temporal distribution of escaped farmedAtlantic salmon in the UK and Ireland, and assess theimplications of the presence of these fish for the ongoingassessment and management of wild stocks.

Using genetic markers to trace escapedsalmon to farm of originVidar Wennevik, Øystein Skaala and Kevin A Glover

In Norway, and other salmon-producing countries, largenumbers of fish escapees are reported each year. Whilstofficial statistics are based upon events that are reportedto the authorities, the real number of fish escaping fromsea-cages is probably much higher, however. There is aneed for a monitoring tool that can trace salmon back tofarm of origin, especially in cases where large numbers ofescapees have been observed without an escapementhaving been reported. Here, we report the results of apilot study investigating the possibility of tracing salmon tofarm of origin using microsatellite DNA and geneticassignment tests. Seven samples from different smoltproducers, and of different strains, were collected fromfour different fish farms located in the Hardangerfjord onthe west coast of Norway. Based upon 11 microsatellites,average assignment of individual salmon to farm of originwas 67%, while assignment between strains was over 90%.This study demonstrates that the use of genetic markersfor tracing escaped salmon to farm of origin may befeasible and should be investigated further.

Density-dependent spawning success andcontribution from farmed female Atlanticsalmon to wild populationsHarald Lura

Spawning success of female Atlantic salmon (Salmo salar)was studied in six Norwegian rivers during 2-4 years.Successful reproduction of farmed salmon was found in 4rivers. Proportions of successful farmed spawners variedbetween 0 and 83 % among rivers and years. Theproportion of successful farmed spawners was positivelycorrelated to proportions of farmed fish in autumncatches and negatively correlated to density of wild fish(r2=0.79). This multiple correlation showed that morethan 30-40 % of autumn catches must be farmed fishwhen densities of wild fish are high, before anycontribution to local populations can be expected. At lowdensity of wild spawners farmed fish perform well. Onaverage, wild females produced larger eggs than farmedfemales. Due to variation in egg weight in wild fish amongrivers, this difference was only significant in two rivers.There were no differences between groups in fertilizationand survival rate. In one river, farmed fish spawned earlierthan wild fish. Salmon domesticated for severalgenerations thus contribute to local populations, but areexcluded at high densities of wild fish, likely due tobreeding competition. The contribution from escapedfarmed salmon in 59 Norwegian rivers during the latestdecade is estimated to 5.2 %, but there was high variationamong rivers.

Estimating impacts of salmon farming onsalmonid survival in the wild: a meta-analytic approach using populationdynamics dataJennifer Ford and Ransom Myers

Time series describing marine survival or abundance ofsalmonids exist in many areas for relatively long periods(30+ years). In this study, we apply population dynamicmodelling to these existing datasets to estimate impacts ofsea cage salmon farming on survival of wild salmonids,using populations less exposed to salmon farming ascontrols. Hypothesized impacts include increasedincidence of disease, competition, and genetic changes inwild populations. Cumulatively, these impacts may beexpressed in wild populations as a reduction in meansurvival, much like the impact of fisheries. Data typesbeing used include catches, returns to rivers, juveniledensities, and escapements, from around the North


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Atlantic and Canada’s Pacific Coast. While significantchallenges to analysis of this data include a high degree ofnatural variation, missing data, and variation in data quality,this approach allows for direct estimation of impacts onnatural populations.

Temporal genetic stability in Atlantic salmonpopulationsØystein Skaala, Vidar Wennevik and Kevin A Glover

Every year, farmed salmon escape from sea cages andhatcheries in high numbers. Selection programmes anddomestication have changed their genetic composition toperform better in the cultured environment, and possiblyworse in natural environments. Therefore, immigration ofhigh numbers of escaped farmed salmon in natural salmonstocks may potentially alter the genetic traits and causefitness changes in wild salmon. To investigate the temporalstability in a number of wild Norwegian salmon stocks,genetic profiles were produced from historical scalesamples and more recently collected scale material.Salmon from Rivers Namsen, Etne, Opo,Vosso, Granvin,Eio and Håelva were genotyped at the followingmicrosatellite loci: Ssa13.37, Ssa28, SsOSL85, Ssa197,Ssa20.19, SsaF43, Ssa202, Ssa85, Ssa171, SsOSL417 andSsOSL438. In Rivers Namsen and Etne no changes wereobserved in DNA profiles between historical and newsamples. In River Vosso genetic stability was observedbetween historical baseline and spawners up to 1997,while a significant change was observed in later yearclasses. This change corresponds in time to year classesspawned after high immigration of farmed salmon. Asignificant change in genetic profiles over time was alsoobserved in River Opo. A reduction in Fst values overtime was observed, indicating reduced level of populationdifferentiation.

Pros and cons of using sterile salmon inaquacultureTillmann Benfey

Sterile populations are useful for the prevention ofspawning of escaped farmed fish in the wild, theelimination of farm production losses associated with earlymaturation and/or the protection of investments made indeveloping novel genotypes. Given the generally reducedperformance of sterile fish in aquaculture to date, the trueneed for sterile populations should be assessed on a case-by-case basis prior to their large-scale use for commercialproduction. This paper briefly summarizes the optionsavailable for rendering fish reproductively sterile, and then

focuses on the pros and cons of using all-female triploidpopulations of Atlantic salmon for aquaculture. The massproduction of all-female triploid populations is easy andinexpensive to achieve, although there are some logisticalconstraints with respect to broodstock requirements.Maximizing the performance of triploid fish requires aclear understanding of their unique biology as well as along-term commitment to selective breeding based ontriploid production characteristics. As yet, neither of theseissues has been adequately addressed through commercialculture; until this is done, the true advantages (anddisadvantages) of sterile salmon cannot be known.

Development in cage technology designed tominimize escapes from salmon farmsArne Fredheim

Escape of fish from fish farms is one of the majorenvironmental impacts caused by modern fish farming.Reduction of the number of escapees has been a majorobjective for the Norwegian fish farming industry inrecent years. The long-term aim is to reduce the extentof escapes to a level where they do not pose a threat tothe wild salmon. The focus on reducing escapes hasresulted in the development of technical requirements forfloating fish farms. Improvement to operations andhandling of equipment and fish to prevent accidents hasalso been considered important. New fish farms have tobe certified according to technical requirements and toprove they have the necessary strength to withstandenvironmental conditions at the particular location.Included in the requirements are user manuals developedby the equipment manufacturers for mounting, handling,operating and maintaining of all equipment. To furtherminimize escapes from fish farms, cage design needs tofocus both on reducing probability and consequences ofaccidents both with regard to technical failure andincidents and to reduce the possibility and consequenceof incorrect use and operation of equipment. Based onsuch aspects, new net cage designs and improved mooringsystems have been developed.

Conflicts between diadromous fishrestoration programmes (e.g. shad, stripedbass) and conservation of populations ofAtlantic salmonDouglas Grout

Anadromous populations of striped bass (Morone saxatilis)are found along the Atlantic coast of North America fromMaine to North Carolina. Recruitment overfishing


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combined with water quality problems led to a substantialdecline in resource abundance during the 1970s and1980s. Cooperative interstate fishery management ofstriped bass began in 1981 when an interstate fisherymanagement plan was developed by an organization ofAtlantic coastal states, the Atlantic States Marine FisheriesCommission (ASMFC). Effective fishery managementunder the ASMFC, combined with several key pieces offederal legislation that strengthened ASMFC managementand provided funding for important research andmonitoring, contributed to a 10-fold increase inabundance of the striped bass stocks by the late 1990s.The dramatic increase in striped bass abundance hasresulted in increased predation on the populations of avariety of species including American shad, river herring,and menhaden. Predation of striped bass on Atlanticsalmon smolts in North America has been documentedbut no quantification of striped bass impacts on stocks ofAtlantic salmon has been conducted to date.

A review of the Pacific salmon hatcheryprogrammes on Hokkaido Island, JapanKentaro Morita,Toshihiko Saito,Yasuyuki Miyakoshi, Masa-akiFukuwaka,Toru Nagasawa and Masahide Kaeriyama

Hatchery programmes involving the mass release ofartificially propagated fishes have been implementedworldwide to supplement wild populations and toincrease harvests. The island of Hokkaido in Japan is oneof the most active regions for Pacific salmon hatcheryprogrammes, with ca. 1.2 billion juveniles released annuallyalong a coastline of ca. 3000 km. In the last quarter of the20th century, coastal catches of chum and pink salmonincreased dramatically, whereas those of masu salmon didnot. In addition to the development of hatcherytechnologies, several possible hypotheses may explainthese catch trends, including climate change, closing ofhigh-seas fisheries, rehabilitation of water quality, habitatloss caused by damming and channeling, and increasedpressure from recreational fisheries. Even when theseother confounding factors have been accounted for, it isstill difficult to evaluate whether all hatchery programmeshave actually resulted in net population increases. To usehatchery programmes more effectively, we need toevaluate river- and species-specific net benefits fromhatchery programmes, and compare hatcheryprogrammes with other management tools, such as fisherycontrols and habitat rehabilitation. Rather than resistingchange, future hatchery programmes should incorporateactive adaptive learning approaches to minimize the risks

associated with artificial propagation, and to promotesustainable salmon stocks.

Loss of regional population structurefollowing stock enhancement in AtlanticsalmonFernando Ayllon, Jose L Martinez and Eva Garcia-Vazquez

Many wild Atlantic salmon populations were enhancedwith domesticated stocks in the past century. To evaluatethe degree and the direction of the genetic changesproduced in wild south European populations bydomesticated stocks, variation at microsatellite loci wasexamined in historical and present scale collections ofseven Spanish and French populations. Significant geneticdifferentiation between neighboring rivers, typical ofAtlantic salmon, existed before stock enhancement butwas lost in only a decade of stocking. Introgression ofdomesticated genomes into local gene pools wasdetected in the studied populations. These results showthat losing genetic diversity is a real threat for wildpopulations subjected to enhancement practices.

Estimates of straying salmon Salmo salarinto rivers on the Swedish Kattegat westcoast from coastal releases in the Baltic SeaStig Pedersen, Gorm Rasmussen, Einar E Nielsen, LarsKarlsson and Per Nyberg

During the years 1995-99 reared salmon from two Balticstrains were released at the islands Bornholm and Møn inthe Baltic Sea. A total of (a) 600,000 reared salmon werereleased from net pens (using the ‘delayed release’technique, keeping the salmon in net-pens for approx.three months after smoltification) and (b) 208,000 rearedsalmon were released directly from the hatchery. Ofthese, 15,958 were tagged with Carlin tags. In the year2000, 65,300 coded wire tagged salmon were released asdelayed release salmon close to Bornholm. Recapturesfrom the Carlin tagged releases varied between 2.8 and26.4% (average 13.1%). Recaptures in the Baltic Seadominated (average 98%), while a minor part of thesalmon were recaptured outside the Baltic Sea, either inthe sea (1%) or in fresh water (1%). Straying rates fromthese releases into six rivers on the Swedish west coastwere estimated using information from various sources(captures in traps, information from the sports- and broodstock fisheries, genetic analysis). The proportion ofstraying salmon was estimated to vary from 1.5 - 2% inRiver Ätran to between 10 and 40% in the River Nissan,with large variation between years. Due to the possible


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deleterious effect on the local wild salmon populations,releases were discontinued.

Changes in wild and hatchery proportions ofannual Atlantic salmon (Salmo salar) catchesin the Baltic SeaMarja-Liisa Koljonen

DNA level information, an 8-loci microsatellite baselinedatabase of 32 Atlantic salmon (Salmo salar L.) stocks, hasbeen used together with a Bayesian estimation method toestimate stock and stock group proportions of Finnishcatches in the Baltic Sea area. The proportions of sevenstock groups important in terms of fisheries managementwere assessed in catch samples taken in four years (2000,2002, 2003 and 2004). In the Gulf of Bothnia area theproportion of wild fish showed a rising trend until 2003 inall areas, but was mainly the result of decreasing totalcatches, which was due to relatively higher mortality ofhatchery fish than of wild fish. In 2004 the total numbersof caught wild fish had also increased, indicating anincrease in the abundance of the wild stocks. In catchesfrom the Åland Sea, the proportion of wild fish increasedfrom 44% to 70% in 2000-2004, corresponding to catchnumbers from 4,628 to 7,329 individual fish. In the Gulfof Finland, the largest contribution was made by localhatchery fish, the Neva salmon, which are released byEstonia, Finland and Russia. In the western part of theGulf of Finland, fish originating from the Baltic Main Basinmade a substantial contribution. The threatened, easternEstonian and Russian wild stocks were recorded only inthe western part of the Gulf of Finland, with a proportionfrom 9% in 2003 to 19% in 2004.

Disease and Parasite Interactionsand Their Management

Parasite interactions between wild andfarmed fishRon Stagg, Rob Raynard and Sandy Murray

This paper will consider both micro- and macro-parasiteinduced disease of fish. Micro-parasites such as bacteriaor viruses are microscopic, they have life cycles that are ofvery short duration into relation to the life expectancy ofthe host (hours versus years) and they tend to elicit astrong immune response in the host. Macro-parasitestend to be larger and to have life spans which are similarin magnitude to the life expectancy of the host and theyonly have weak interactions with the host immune system.

Epidemics of micro-parasitic organisms are associated withthe dynamics between susceptible, infected and recovered(immune) hosts and are therefore associated with thenumber of infected hosts. In contrast macro-parasiticepidemics are associated with both the number ofinfected hosts and the intensity of infection. In both casessuccessful invasion of the host by the parasite and thespread or evolution of an epidemic is indicated when thebasic reproductive number (Ro) is greater than one. Thisoccurs when a host infected with a micro-parasite givesrise to more than one secondary infection or a macro-parasite produces more than one offspring surviving toreproductive age in the course of its life. Parasiteepidemics can affect both farmed and wild fish and haveconsequences for both: population regulation in wild,economic damage and welfare effects in farmed fish as aresult of losses, decreased growth or trade limitations.Wild fish are the ultimate source of parasites and can alsobe a reservoir of infection which impedes eradicationprogrammes in farms. However, the farming of fish canexacerbate disease problems through the promotion ofconditions leading to epidemics (such as enhancedtransmission and evolution), long-range transport (throughtrade and introductions) and spill-over of parasites backinto the wild. Normally there is a balance between theability of the host to resist invasion and the ability of theparasite to reproduce successfully. Maintaining fish inculture can alter this balance such that epidemics aremore likely. The rearing of fish under aquacultureconditions, with good husbandry and management, shouldnot necessarily cause reduced resistance to parasitesbecause of stress in the host. Much more important willbe the impact of culture conditions on the transmission ofinfection, particularly the contact rate between susceptibleand infected hosts and the duration of infection. Althoughoriginating in wild populations the emergence of parasiticinfections is an inevitable consequence of farming fish andthis is illustrated by an examination of some of the moreimportant diseases that have emerged in Scottishaquaculture in the past 20-30 years. However,examination of some of these case histories also indicatesthat epidemics in farmed fish do not necessarily result inepidemics in wild populations and that managementmeasures such as good bio-security and husbandry can beeffective risk mitigation measures.

Sea lice biology and geneticsKarin Boxaspen

Studies of sea lice biology, including both the species


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Lepeophtheirus salmonis and Caligus elongatus, have beenconducted from various perspectives over the last twodecades. Pike and Wadsworth last reviewed parts of thistopic in 1999, but new research and the application ofgenetic methods to certain aspects of the problemnecessitates an updated review. The focus of this researchhas been in areas such as life-history biology, study ofdevelopmental stages under different and varyingconditions (temperature and salinity), behaviour,distribution of sea lice and dispersal of free-living stages,monitoring practices, population structure and modelling.The results of this research have been used to refinemanagement strategies and risk analysis concerning sealice infections in wild and farmed populations ofanadromous fish. Studies implementing methods basedon molecular biology have been used to describepopulation structure, possible differences in geneticcharacterization of geographically separate populationsand population markers. Susceptibility to sea lice and thepotential for selective breeding have also been addressed.To try and understand the parasite/host relationships at amolecular level, work has been started to characteriseproteins and the main aim of the work is to explore thepossibility of developing a vaccine against sea lice.

Impacts of salmon lice on wild salmonidsBengt Finstad, Pål A Bjørn, Jens Christian Holst, Peter AndreasHeuch, Roar Kristoffersen, Chris Todd, Neil Hazon, PaddyGargan, Oliver Tully and Scott McKinley

Research carried out over the past 15 years has indicatedthat salmon lice must presently be regarded as apotentially important population-regulating factor in manysalmonid stocks. Their actual detrimental impact, in termsof absolute reductions in the sizes of the total wild salmonrun, is, however, uncertain due to a lack of systematicinvestigations. Methods to assess salmon lice infestation ofseaward-migrating post-smolts in the early stages of theirmarine phase have now been successfully developed. Asa precautionary measure, the salmon farming industry hasintroduced various strategies to reduce the numbers ofsalmon lice larvae in many aquaculture areas, and hencethe potential horizontal and vertical transmission to wildfish. The effects of these reductions are probably mostlybeneficial to the wild salmon stocks. This presentationsummarizes current knowledge on interactions betweenlice on farmed and wild salmonids, including theoreticaland empirical studies of lice production and infestationdynamics, routes of transmission and monitoring datafrom Norway, Ireland and Scotland.

Temporal changes in genetic variability inwild sea trout (Salmo trutta L.) from twoIrish rivers affected by Atlantic salmonaquacultureJames Coughlan, Elvira de Eyto, Eileen Dillane, Ola Diserud,Philip McGinnity, Brian O’Farrell, Killian O'Farrell, Rene Stetand Thomas Cross

Several studies have documented the harmful geneticeffects of intra-specific hybridisation of reared and wildAtlantic salmon (Salmo salar L.). However, the effects ofsalmon aquaculture on wild congeners are less wellunderstood. Since the late 1980s, severe sea troutdeclines have occurred in many Irish rivers, thought to becaused by sea lice infestations associated with fish farming.The effects of other introduced diseases are also likely toaffect wild salmonids. Here, we analyse how theintroductions of diseases associated with intensive salmonfarming and ranching have had an impact on the geneticvariability of cohabiting sea trout. We compared variationat a locus critical to immune response (MHCI) withvariation at six neutral microsatellite loci. Sea troutsamples (archived scales) were investigated from tworivers (the Burrishoole and Erriff) both with a history ofaquaculture. A substantial decline in allelic richness andgene diversity at an MHCI marker, that was observed inboth rivers since aquaculture started (which may be anindication of a selective response in the two populations),was not reflected by similar reductions at neutral loci inthe Burrishoole system. In the case of the Erriff, both theMHCI and the neutral markers showed evidence of areduction in genetic variability. Subsequent recovery ofvariability at MHCI seen among the later Burrishoolesamples was not apparent in the Erriff trout. Thedifferences in the observed temporal patterns of geneticvariability between the two rivers may reflect the relativeproportions of sea trout to freshwater-resident fish inthese systems.

Stress and osmoregulatory dysfunction inlaboratory-controlled sea lice infestation ofsea troutAlan Wells, Christal Grierson, Iain Russon, Sjoerd WendelaarBonga, Paal Bjorn, Bengt Finstad, Chris Todd and Neil Hazon

Since 1989, sea trout stocks on the west coasts ofScotland and Ireland have declined catastrophically,accompanied by widespread observations of ‘prematurereturn’ of post-smolts to fresh water, within a few weeksof their first migration to sea. These fish typically bore


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heavy infestations of largely juvenile stages of sea lice. Weundertook laboratory-based infestation of wild sea troutsmolts with Lepeophtheirus salmonis, in order to determinethe threshold levels of sea lice which induce sub-lethalphysiological stress and osmoregulatory dysfunction. In aparallel series of experiments for sea-lice infested post-smolt sea trout, we also examined the physiologicalconsequences of premature return to fresh water. Theosmoregulatory ability and status of these fish wasassessed by a variety of physiological, biochemical andhistological techniques including branchial, intestinal andrenal Na+K+-ATPase activity, plasma ion composition, anddrinking rate. Stress was assessed by determination ofplasma levels of cortisol, MSH, glucose and lactate andliver glycogen levels. In addition, the integrity of skin andgill tissue was assessed by SEM,TEM and confocal laserscanning microscopy. This suite of analytical techniqueshas allowed us to estimate the sea lice infestation levelsthat trigger sub-lethal, chronic and acute physiologicalstress in sea trout.

Survival and growth of sea-ranched Atlanticsalmon treated against salmon lice prior toreleaseOve T Skilbrei and Vidar Wennevik

Smolts were treated with SLICE® (orally administeredemamectin benzoate) prior to releases in the River Dale,western Norway, to study the potential effects of salmonlice during the early stay in the sea. A total of 10,470treated and control fish of 10 family groups were adiposefin-clipped, micro-tagged, and released in the Dale Riveron three different dates in 2002: May 11, May 25 and June7, in accordance with the timing of the natural smolt run.Grilse returns in 2003 did not differ between the treatedand control group smolts released in May 2002, but thegrilse returns from the treated smolts released on 7 June2002 were almost twice those derived from theuntreated control group. The weights of the grilsegenerally declined from the first to the third release date,and the treated fish were approximately 15 % heavierthan the controls. The higher return rate of smoltstreated and released on June 7 was also observed for the2-sea-winter salmon in 2004. We conclude that theinfestation level of salmon lice changed from non-lethal tolethal levels during the period of the smolt migration, andthat non-lethal infestation levels may considerably affectAtlantic salmon by reducing growth rate and spawningsize.

Exceptional production of pink salmon in2003/2004 indicates that farmed salmonand wild Pacific salmon can coexistsuccessfully in a marine ecosystem on thePacific coast of CanadaRichard J Beamish, Simon Jones, Chrys-Ellen Neville, RustonSweeting, Grace Kareman, Sonja Saksida and Elysha Gordon

Juvenile pink salmon that entered the marine waters in amarine ecosystem along the eastern margin of QueenCharlotte Strait in 2003 and returned as adults in 2004had very high marine survival. The early seawardmigration and mid-summer rearing in 2003 was in an areacontaining 16 active Atlantic salmon farms. Two species ofsea lice were commonly found on farmed salmon andwild salmon. The exceptional marine survival of pinksalmon indicates that pink salmon populations and farmedsalmon coexisted successfully in 2003.

Susceptibility to the sea louse(Lepeophtheirus salmonis), InfectiousSalmon Anemia and Furunculosis amongsalmon of wild, farmed and hybridparentageKevin A Glover

Genetic differences between Atlantic salmon of wild andfarmed backgrounds have been observed for a variety ofbiological, behavioural and life-history traits. Notably,several authors have demonstrated that salmon of farmedparentage display reduced survival in natural ecosystemscompared to the offspring of wild parentage. Despitethese key differences however, at present, potentialdifferences in susceptibility to disease have been littleexplored. Susceptibility to disease represents animportant aspect of fitness under both domestic andnatural environments. It is also conceivable that geneticdifferences in susceptibility to disease may exist betweensalmon of farmed and wild parentage due to the differentselection regimes they are exposed to in their respectiveenvironments. Here, we summarise the results of fourstudies where salmon of wild, farmed and hybridbackgrounds have been compared in their susceptibility tothe sea louse (Lepeophtheirus salmonis), Infectious SalmonAnemia and Furunculosis. Together, results from thesestudies indicate that large and systematic differences insusceptibility to disease are unlikely to exist among salmonof farmed and wild parentage. It is recommended,however, that this topic deserves further investigation.


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Salmon lice infection of running Atlanticsalmon in two Norwegian fjords: effects ofhydrography and lice abundancePeter Andreas Heuch, Jens Christian Holst, Lars Asplin, BengtFinstad, Pål A Bjørn and Audun Stien

Research carried out during the 1990s identified salmonlice as a potentially serious population-regulating factor inNorwegian salmonid stocks. Various managementmeasures were imposed, amongst them a veterinarian actin 1997 regulating the numbers and stages of salmon liceallowed per individual fish in farms. Through acomparative study between two major salmon fjords,Altafjord and Sognefjord, we focused on interactionsbetween salmon lice and wild and farmed salmonids. InAltafjord the results indicate that salmon lice were never aproblem for migrating post-smolts of salmon, while in theSognefjord the conditions have gone from negative before2002 to good during 2002-2004. This coincides with thefish farming industry’s efforts to reduce the salmon liceproduction in the farms in the critical spring period.Hydrographic-biologic modelling of data from Sogn from athree-year period showed that environmental factors donot explain the reduced infection of the running salmonsmolts. For sea trout the situation seems less positive. Aclear reduction of salmon lice infection intensity on seatrout was not recorded in either the Altafjord or in theSognefjord. It is concluded that wild and farmed salmoncan coexist in Norwegian fjords if the total amount ofsalmon lice larvae in the fjord is adapted to the localhydrographic conditions and the population characteristicsof the wild salmonids. To ensure precautionary salmonlice management in Norwegian fjords there is a need formore knowledge on environmental and biologicalparameters, in particular where there are plans forincreasing the output of farmed fish.

Two-year sea lice larvae plankton surveyMichael J Penston, Ian M Davies and Alain F Zuur

An extensive plankton survey was carried out in the LochTorridon system, on the west coast of Scotland, toinvestigate sea louse infective pressure. The surveyconsisted of plankton tows collected weekly at a numberof sites within the sea loch over a 2-year period, between2002 and 2004. In total, 884 samples were collected and8,382 lice larvae were recovered, of which 58% werenauplii and 42% were copepodids. The species of thenauplii were not determined, but copepodids wereretained for identification. From the 416 samples

containing preserved copepodids, a random selection of102 samples were examined for the presence ofLepeophtheirus salmonis and Caligus elongatus. The vastmajority of the copepodids retained were L. salmonis, andonly a few were C. elongatus. During the survey, salmonfish farms in the Loch Torridon system completed aproduction cycle. Generalised Additive Models (GAMs)were used to describe the distribution of lice larvae. Themodels suggested an increase in larvae densities duringthe farm production cycle, followed by a decrease as thefarms harvested and were left fallow. Significantly greaterdensities of copepodids were recovered at the surfacethan at 2.5 and 5 metre depths. Nauplii showed nopreference for any of the depths sampled. Densities ofsea lice larvae were found to vary considerably, rangingfrom 0 to 243 larvae m-3. This high variability in the datawas also indicated in the GAM models.

The current state of health management inaquaculture - progress to date and futurechallengesGraeme Dear and Edward Branson

Fish health management has developed from being a ‘newconcept/minor species/green-fingered/let’s try it and see’aspect of aquaculture to one which increasingly utilises themost advanced scientific technology to provide solutionsto health challenges. The current status of fish health andoptions available to the farmer to control pathogens aredescribed in the context of a rapidly evolving industry.The inter-relationship between the key parameters oflegislation, economics, environment, host, consumerconcerns and veterinary medicines are examined in thecontext of reducing antibiotic use and increasing pressureto control parasitic and viral diseases such as sea lice,IPNV and pancreas disease. While vaccine availability andhusbandry methods have advanced to the point wherethey have reduced, but not eliminated, the need forantibiotics, the future challenges revolve around theimportance of a greater understanding of the needs ofaquaculture healthcare. In an environment which isincreasingly demanding from regulatory, environmental,retailer, consumer and wider stakeholder interests - it isimportant not to forget the main purpose of the subject,i.e. fish health and welfare. These challenges will bediscussed and key areas identified for veterinary care andfuture research and development to assist in themanagement of fish health.


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Trends in the usage of drugs in NorwegianaquacultureKari Grave and Tor Einar Horsberg

All use of drugs in farmed aquatic organisms in Norway isprescription-based. Such drugs have to be dispensedthrough pharmacies or authorized feed mills and this hasfacilitated the establishment of a comprehensivesurveillance programme on drug usage in fish farming inNorway. The main aim of this surveillance system is tocarry out risk-based drug residue control, but the dataobtained are also used to make public valid drug usagedata in aquaculture. Such statistics might be used toassess the environmental consequences of drug use in fishfarming regionally or nationally, i.e. impact on wild salmon.The present paper will focus on impact of use of themajor drug groups (antibacterial drugs and drugs againstsalmon lice infestations) in Norwegian fish farming, andbasically discuss consequences for wild salmon. It isconcluded that use of drugs in fish farming is unlikely tocause any toxicological harm to wild salmon. In Norway,drug use in aquaculture is considered unlikely to be afood safety problem as regard wild salmon, e.g. causingdrug residues. However, in countries/regions withintensive farming and extensive use of drugs, food safetyrisks might be considered. Regarding use of drugs againstsalmon lice infestations, it is concluded that suboptimaltreatment against salmon lice infestations is likely to resultin heavy salmon lice infections and consequently increasedmortality in smolt approaching the sea. Likewise,extensive treatment increases the risk for resistancedevelopment which may result in a poor effect of thedrug within the farm and consequently an increased riskfor wild salmonids.

The Scottish Tripartite Working GroupApproach: Building consensus and makingprogress to protect wild fish interestsalongside salmon farmingPhil Gilmour

The objective of the Scottish Tripartite Working Group(TWG) approach is to bring together, under a voluntaryinitiative, the salmon farming industry, the wild fish sectorand Government to facilitate discussion and co-operation.Consensus between the three parties is being, and willcontinue to be, improved through the sharing ofinformation and development and implementation of areamanagement agreements (AMAs). AMAs provide localsolutions to maximise the effectiveness of sea lice

management and control and bring additional benefitswhich minimise fish disease risks. Another issue coveredin AMAs is the minimisation of escapes of farmed fishwhich can have the potential to interbreed withgenetically unique wild salmon stocks. Reachingagreement on containment and contingency planning tominimise escapes of farmed fish and facilitate efforts torecapture them is also covered within the AMA process.Three regions of Scotland (Argyle and Lochaber, north-west Scotland and the Western Isles) were targetedbecause of the presence of both salmon farms and wildfish interests. Twenty areas were originally identified assuitable for the development of AMAs. It is hoped thateighteen AMAs will have been signed before the end ofthis year. This will represent good progress over thesecond stage of the TWG process, covering the period2003-2005. The costs of staff resources and projects overthis timescale comes to almost £1 million.

Use of wrasse in the control of sea lice onfarmed salmonPer Gunnar Kvenseth, Johan Solgaard and Kristin Ottesen

Concerns over the negative effect of sea lice on farmedand natural stocks of salmonids, and the environmentalconcerns over chemicals used to control sea lice in thesalmon farming industry, have resulted in the search foralternative treatments. One successful alternative involvesthe use of cleaner fish, where one species of fish (thecleaner) feeds on parasites from another fish (the host).Widely used as cleaner fish within the Norwegian salmonfarming industry are several species of wrasse (familyLabridae). All wrasse used to date have been caught bytraps in the wild. New research is now developingmethods for the culture of wrasse. Given the rightconditions wrasse is one of the most effective, cost-efficient and environmentally benign ways of controllingsea lice on farmed salmon. Cleaner fish, used correctly,will keep the level of sea lice at a continuous low level onfarmed salmon. Stomach content analysis has shown upto 272 pre-adult/adult lice in one ballan wrasse. Over 40% of ballan wrasse examined were found to haveconsumed sea lice. Wrasse will also control sea licereproduction as they prefer grazing on pre-adults andparticularly adult female lice. Sea lice eggs do not surviveor hatch after passing through the gut of a cleaner fish.Updated information on results and protocols are givenon www.leppefisk.no.


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Control and treatment of GyrodactylussalarisJarle Steinkjer and Edmund Peeler

Gyrodactylus salaris is a freshwater, monogenean ecto-parasite of Atlantic salmon. Infection of its original host,Atlantic salmon in the Baltic watershed, is generallyinapparent. It is only on Atlantic stocks of Atlantic salmon(Salmo salar) that the parasite multiplies uncheckedcausing a high level of mortality in juveniles and,consequently, dramatic reductions in wild populations. In1975 the parasite was introduced into Norway, probablythrough the importation of Atlantic salmon smolts fromthe Baltic region, and has dramatically reduced stocks ofAtlantic salmon in 45 rivers. It is known to be present inDenmark and Germany and is likely to have beenintroduced into other European countries with theimportation of live rainbow trout (only the UK and Eirehave demonstrated freedom from the parasite). G. salariscan infect rainbow trout (Oncorhynchus mykiss)permanently, and cause infection of up to 50 days inseveral other species. In this paper the action planimplemented by the Norwegian authorities to combat theparasite will be reviewed. The plan includes surveillanceto ensure early detection, prevention of the spread of theparasite to uninfected rivers, and measures to eradicatethe parasite through chemical treatment and barriers tomigration. Chemical treatment has been implemented ina total of 27 out of 45 infected watercourses in Norway.For countries such as the UK and Eire that are free of theparasite, and have significant stocks of potentiallysusceptible Atlantic salmon, preventing the introduction ofthe parasite is the major objective of any controlprogramme. However, contingency plans to minimise theimpact of the parasite, if introduced, are also critical.Restriction of live fish movements is central to the controlof the spread of G. salaris between catchments. Thepotential importance of other routes (e.g. fishing gear) willbe considered in the light of the survival characteristics ofthe parasite off the host. Differences in the control of G.salaris in Norway and the UK will be discussed.

Poster PresentationsSonic tracking of wild cod, Gadus morhua, inan inshore region where cod aquaculture isdevelopingPaul Brooking, Gino Doucette and Fred Whoriskey

East Coast North American finfish farmers are beginningto diversify into the culture of fishes other than Atlantic

salmon. Sea cage trials have begun with Atlantic cod(Gadus morhua). We fitted inshore wild cod with sonictags during the summer of 2004, to provide data on thehabitats they used, their temporal residency, and theircoastal movements. This information can help determinethe potential for interaction among wild and escapedfarmed cod, and escaped cod and other species. Wildcod remained within a restricted corridor in the inshorezone. They generally concentrated in deep holes (~ 100m) but undertook local movements, possibly related tofeeding. There was a gradual movement offshoredetected as winter advanced, with fish of reproductive sizemoving away first, possibly to offshore spawning areas.One fish was still present in February 2005. Cod, knownAtlantic salmon smolt predators, resided in the principalmigration corridor for smolts from severely depressedwild Atlantic salmon populations. If escapes of farmedcod occur, and they occupy the same habitats as their wildcounterparts, it could increase predation upon salmonsmolts. Siting and engineering of cod farms should bedone to minimize the probability of escapes.

Genetic variation after and before theAtlantic salmon supportive breedingprogramme in the rivers Ulla and Lérez(Galicia, Spain)Maria Saura, Pablo Caballero, Armando Caballero and PalomaMorán

Management of wild Atlantic salmon (Salmo salar L.)populations based on stocking procedures has beenwidespread over the European range of this speciesduring the second half of the past century. In southernEuropean rivers, stock transfers from northern Europeancountries have been justified by a severe decline in nativepopulations. However, the efficiency of this type ofmanagement to increase effective population size hasbeen very poor, mainly because the stocks employed forsupplementation presented genetic characteristicsdifferent from those of native populations. Since 1995, allsalmon released in the rivers Ulla and Lérez (north-westSpain) are descendants of naturally returning adults and ofwild parr reared until the spawner stage wholly in freshwater (holobiotic rearing), artificially mated in Carballedohatchery. The success of this supportive breedingprogramme has been monitored using physical markers,and the results seem to be satisfactory. To investigate thegenetic variability ten years after the beginning of theprogramme and to test the genetic differences betweenthe present-day populations and those before the


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restoration programme, genetic variation at fivemicrosatellite loci was analysed in a collection of old scales(1950-1965) and samples from modern returning adults(1998-2004), including individuals born in the river and inthe hatchery. Heterozygosity values and average numberof alleles are very similar in modern and old populations.Populations inhabiting the rivers Ulla and Lérez are moresimilar nowadays than they were in the past. Althoughthe present Ulla and Lérez populations were initiallyrestored using a stock mix from other Galician rivers(including the River Ulla), there are genetic differencesbetween both populations, suggesting some degree oflocal adaptation and low straying rates.

Distribution and biological characteristics ofescaped farmed salmon in a major subarcticsalmon river (River Teno, Finland/Norway)Eero Niemelä, Jaakko Erkinaro, Jukka-Pekka Vähä, Craig RPrimmer, Sturla Brørs, Esa Hassinen and Maija Länsman

Escaped salmon from Norwegian fish farms in the ArcticOcean show a wide spatial dispersion in the largesubarctic river Teno, northernmost Scandinavia, supportingperhaps the largest wild Atlantic salmon stock complex inthe world. Farmed salmon were caught throughout the>250km-long main stem and major tributaries during thefishing season (June-August) in 1987-2004 when theproportion of escapees in catch varied between 0.08 and0.53%. However, the number of escapees increasedtowards the end of the fishing season. The proportion ofwild 1-5SW salmon caught in August represented 15-25%of the total catch, whereas the corresponding proportionfor the escaped salmon was as high as 69%. Experimentalsampling after the season (September-October) hasrevealed high proportions of escapees, up to 50%. Weightof the escaped salmon varied between 2 and 10 kg. Upto 88% of the escaped salmon caught in August showedsignificant gonad development, and there are also directobservations of escapees on spawning grounds during thebreeding season. This reflects high potential for successfulreproduction of escaped salmon. Scale analysis indicatedthat 4.5% of the escaped salmon were repeat spawners.Highly significant genetic differentiation was observedbetween wild and escaped farmed salmon captured in theriver.

Towards sustainable salmon aquaculture -zoning of the Icelandic coastlineSigurdur Gudjonsson

Over 100 Icelandic rivers foster natural salmonpopulations that are considered as important parts ofIcelandic nature. Sport fishery of Atlantic salmon is veryimportant for Iceland with annual turnover ofapproximately 125 million euros. Large fishing companiesshow interest in salmon cage rearing. Cage rearing ofsalmon was tried in Iceland in the 1980s and 1990s butwas not successful, as conditions are harsh around Iceland.Salmon has been farmed in land-based units since the1980s. Interested salmon farmers claim that cage rearingaround Iceland can be successful today because of bettersalmon strains, better cages and better knowledge. Theyhave also argued that salmon farming can be important inIceland, creating jobs and improving the economy in ruralareas. River owners fear that only a few farmed salmon intheir river can harm the image of their pristine river andsalmon. Furthermore, river owners and environmentalistsfear that salmon cage rearing will threaten the valuablewild stocks, as salmon escapees from the cages willmigrate to the rivers, cause genetic mixing and breakdownof the local adaptation of the stocks, as well as spreadingparasites and diseases. They fear that eventually it willleave the rivers without salmon, ruining their income.Discussion and debate of these different views has beengoing on in Iceland. Positive and negative sides of salmonfarming in other countries were evaluated. The Icelandicparliament, Althingi, passed new legislation on fish farmingenabling the government to manage fish farming better.Salmon farming is not allowed in the bays and fjords withthe most valuable salmon rivers. This was considered as astep towards sustainable salmon farming and as acompromise between these opposing views. Salmonfarming is only allowed in certain areas and theexperience gained there will be used for furtherevaluation and development of salmon farming in Iceland.

Use of catch statistics to monitor theabundance of escaped farmed salmon andrainbow trout in the sea in a region ofwestern NorwayOve T Skilbrei and Vidar Wennevik

Catch statistics and scale samples have been collectedfrom a gill net fishery targeted for escaped farmedsalmonids (1 October - 28 February) for the years 2001 -2004 in Hordaland County, western Norway. An attempt


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has been made to classify the fish into different groups, orescapement events, by using catch per unit effort (catchper net per day) and size distribution of the catch fromdifferent geographical sub-regions. In addition, thegenotypes of some sub-samples are compared. It isconcluded that most of the escaped farmed fish were oflocal origin and that catch per unit effort may be a usefultool for monitoring escape incidents and the relativeabundance of escaped farmed fish. There were clearindications of a decline in the stock of escaped rainbowtrout during the fishery.

The feeding behaviour features of culturedand wild salmon in Kola Peninsula riversAlexander V Orlov,Yuri V Gerasimov and Oleg M Lapshin

In order to investigate the behaviour and distribution ofyoung salmon and adaptation of cultured fish to thenatural environment, an underwater survey wasconducted on the Shugor and Luvenga rivers. Behaviourwas examined, current speed measured and drift samplescollected. The food and feeding habits of 34 wild and 44cultured smolts released from the Kandalaksha fishnursery were also studied. The young fish moved freelyover the area in all directions, 5 to 10 m away, stoppingevery 1 to 2 m. They became somewhat aggressive onlywhen, on very rare occasions, they moved within 0.3 m ofeach other. From about the same distance the parrwould flee from the approaching observer. The young fishmostly fed in the bottom 15 cm of the water column,with current speeds of 0.2 to 0.35 m/s, making 5 to 10 cmfeeding lunges every 20 seconds. When cultured fishmoved from these areas into areas with higher currentspeeds (average speeds of 0.5 m/s) and lower drift density(2.55 species/m3) they did not show a tendency to returnto slower-moving water, unlike wild fish. The smolts fed onbottom invertebrates carried with the current, and insectswhich had fallen onto the surface of the water. Thecultured fish had a significantly larger share of the formerin their diet (40% and 25% respectively). Few of the fishexamined had empty stomachs so it may be assumed thatboth the wild and cultured smolts were feeding actively.However, on the basis of the average food quantity perstomach it may be assumed that the wild smolts werefeeding more actively than the cultured ones.Invertebrate content in the above rivers is 3% of the totalquantity of formed particles, the remaining 97% beingexuvium of aquatic and terrestrial insects, algae andvarious plant remains. Non-feed remains were found in13% of wild and 25% of cultured salmon, i.e. the cultured

smolts are less capable of differentiating food in the water,making more false food lunges (from 20 to 30%) thanwild fish. The cultured fish were more aggressive, in termsof the frequency of brawls, with individual fish reacting toeach other from larger distance. Wild smolts would fleeto escape from the closing observer, while the culturedfish would allow the observer to come closer. Thecultured and wild fish have generally similar diet andfeeding behaviour. Certain differences, however, wereobserved in the saturation ratio and distance of responseto feed, to each other and to the diver.

Physiological and behavioural effects ofintrogression of salmonid fast-growingdomestic genotypes into non-selectedgenetic backgroundsWendy Tymchuk and Robert H Devlin

Domestication in fish often involves direct selection forimproved growth rates as well as other correlated traits,and can therefore have a significant impact on life history.Many fitness-related traits, such as growth, competitiveability and anti-predator behaviour, have been found tohave a genetic component. Due to an altered selectionregime, the cultured fish may not be as adapted to thenatural environment as wild fish. This researchsummarizes the growth, behaviour and physiology of fast-growing (domesticated aquaculture), slow-growing (non-selected), and hybrid (F1, F2 backcross, and F3 backcross)strains of coho salmon (Oncorhynchus kisutch) andrainbow trout (O. mykiss). Growth of the strains wascompared under both culture and semi-natural rearingconditions. Under all environments, there was a strongcorrelation between growth and the proportion ofdomestic genes within the genotype. Comparisons ofanti-predator behaviour and hormone profiles illustratedsimilar trends. Assessment of the expression of fitness-related phenotypes in the hybrid strains can provideinformation on the genetic changes that have evolvedduring the domestication process. Knowledge of thegenetic changes responsible for altered growth rates infish is crucial information needed to increase our ability topredict the consequences of introgression between fast-and slow-growing strains of fish.

Genetic history of a restoration river, theConnecticut RiverFernando Ayllon, Stephen Gephard, Francis Juanes and EvaGarcia-Vazquez

The Connecticut River lost its Atlantic salmon population


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due to human activity 200 years ago. Foreign hatchery-reared stocks were employed to restore the population.An annual run of salmon has been successfully re-established, although that population is not yet self-sustaining. We have examined variation at microsatelliteloci in historical and modern scale collections to evaluatethe degree and the direction of the genetics changesoccurred in the introduced stocks. The current geneticpattern of the Connecticut River restoration populationwas very similar to that of its Penobscot River donorpopulation. We found no difference in heterozygosity,mean number of alleles per locus, number of migrants, orFST values, all suggesting that no gene drift or foundereffects have occurred. Differences between the donorand the derivative populations for both sea-run age andallele frequencies at the isozyme locus MEP-2* are likelyadaptive responses to environmental variation.

Interactions between acidification in freshwater and sea lice sensitivity as anunderlying factor causing delayed responsesFrode Kroglund, Bengt Finstad, Sigurd O Stefansson,TorsteinKristensen, Bjørn O Rosseland, Hans C Teien and Brit Salbu

Severe acidification is acknowledged as the cause for theextinction of numerous Atlantic salmon (Salmo salar L.)populations in Southern Norway. Acidification mobilizesaluminium (Al) from the soil, resulting in elevated Alconcentrations in the freshwater ecosystem. In freshwater, cationic (labile or inorganic) forms of Al (Ali)accumulate onto fish gills, where gill-Al concentrationsexceeding 250 µg Al/g gill dry weight are associated withincreasing mortality due to respiratory and ionoregulatorydysfunction. At lower concentrations, fish health can stillbe affected (measured as reduced growth), althoughblood ion levels can remain within a range that is normalfor pre-smolts. However, at these concentrations, Al maystill interact with gill Na+K+-ATPase and inhibit enzymeactivity. Reduced Na+-K+-ATPase activity is associatedwith poor seawater performance. An exposure to Al hasno observable effect on the timing of, or the behaviourduring, downstream migration, but a gill-Al concentrationof 20 to 50 µg Al/g gill dry weight is sufficient to reduceadult return rates by 20 to 50 % relative to the untreatedcontrols. Acidification had a delayed effect, where theresponse is reduced post-smolt to adult survival.Following entry into seawater, Na+-K+-ATPase activity isrestored to normal levels over the first few weeks.During this recovery phase, the post-smolt is morevulnerable to predation due to the poor hypo-

osmoregulatory capacity affecting anti-predatorybehavioural traits like avoidance. Fish that survive thisinitial phase appear to adapt fully to sea water, as growthand the age of adult returns were not very different fromthe controls. Pre-smolts, first exposed to sublethal levelsof Al in slightly acid water (pH 5.8; 5-15 µg Ali/l) for aperiod of days (episode) to weeks (long-time), then to apost-exposure treatment to sea lice (Lepeophtheirussalmonis Krøyer) copepodids, indicate additional andhitherto unpublished delayed effects that also havepopulation responses. Infestation of the post-smolt withcopepodids had no adverse effect on hypo-osmoregulatory capacity before the sea lice reached adultstages. After 42 days, the acid-exposed fish infected withsea lice suffered elevated mortality in an Al-dose-dependent manner relative to the same untreated groups.The sub-lethally Al-exposed smolt appears to be moresensitive to disease and parasite attacks suggesting areduced tolerance to additional stressors. Many of thesalmon-bearing rivers on the South-western coast ofNorway can be periodically acidified to sublethal levels forperiod lasting from days to weeks prior to and during thesmolt run. This is also a region heavily populated with fishfarms. The combined effects of moderate acidification (infresh water) and moderate sea lice infestation (in seawater) can have the same devastating effects as higheracidification levels or higher sea lice densities. Year to yearvariations in acidification pressure and salmon licedensities can in combination obscure, but also explain,some of the year to year variation in post-smolt survivaland hence the variation in Atlantic salmon year-classstrength in Norwegian rivers located along the south-western coast. Rivers on the South coast are mainlyaffected by acid rain, while more northern rivers are notaffected by acidification. As many salmon populationsencounter multiple stressors, caution should be usedtowards using single pressure explanatory models.

Infection success of salmon lice(Lepeophtheirus salmonis) related totemperatureKarin Boxaspen

The development rate for salmon lice larvae is highlytemperature-dependent. Hence, the time from hatchingof nauplii to an infectious copepodid will vary with thenatural cycles in the sea and the copepodid’s life span isprolonged at lower temperatures. This has implicationsfor dispersal of larvae in the environment and thesubsequent decision of what is the sensible regional size


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of salmon farming areas. The infection success of salmonlice as a function of copepodid age have been studied incontrolled systems from 6°C to 14°C. Newly hatchedsalmon lice were collected every day from a hatchingsystem and placed in holding units. Copepodid groups ofspecific and different age were used to infect salmon in atemperature-controlled system and the successful moultto chalimus recorded. The salmon lice were, as expected,infectious for a longer time at the lower temperatures.The maximum staying time from hatching to lastsettlement observed for one individual was found to be30 days (at 6°C).

Measuring the impact on the naturalproduction of Atlantic salmon (Salmo salar,L.) of native origin hatchery fish spawningin the wildPhilip McGinnity

There has been a dramatic and persistent decline inAtlantic salmon numbers throughout most of the species’geographical range. This decline in wild stocks has led towidespread releases of artificially spawned and rearedAtlantic salmon in an attempt to supplement naturalproduction. ‘Common garden’ experiments undertakenunder natural river conditions, show that geneticdifferences among wild and hatchery populations, result insignificant performance differences that led to a reductionof productivity, particularly in environments where density-dependent mortality factors are important regulators ofsurvival. However, no studies have shown, either in realtime or retrospectively, losses in natural production innon-experimental wild populations of Atlantic salmon as aresult of the deliberate release of hatchery fish. Spawner-recruit relationships provide a valuable conceptualframework for predicting and may, in those few instanceswhere they exist, provide a practical opportunity ofmeasuring the effects of genetic alterations or geneticdifferences between populations on the productivity andabundance of Atlantic salmon. Here, I present an analysisof stock and recruitment data for a population receivingvariable, but significant quantities of naturally spawninghatchery fish over a 35-year period, as an indirectmeasure of changes in the productivity of a naturalpopulation. It is significant that the hatchery populationwas founded from the wild population investigated andthus might be thought to represent the most geneticallysuitable material for stock enhancement. An analysis ofthe residuals from the stock and recruitment relationshipsuggests that a significant proportion of the variation

around the relationship can be explained by theproportion of naturally spawning hatchery fish and thatthese incursions have had a significant depressive impacton the recipient population of approximately 30%.Removal, rather than addition, of hatchery fish, therefore,may be the most effective strategy to improveproductivity and resilience in natural populations.Hatchery fish have effectively been excluded fromspawning in the wild in this river for the last eight years; asignificant improvement in the freshwater production ofsalmon smolts has followed.

Movements of cultured salmon in aNorwegian fjord systemOve Skilbrei, Jens Christian Holst, Marianne Holm and OleTorrissen

A study has been initiated in 2005 in a Norwegian fjordsystem to study the behaviour and movements of escapedAtlantic salmon. Adult salmon (2-4 kg) from a commercialfish farm are tagged with coded acoustic transmitters withdepth sensors and released at different dates. A total of24 data-logging receivers record the movements andswimming depths of the simulated escapees at variouslocations in the Hardangerfjord. Some examples from thefirst recordings are shown. They show that severalindividuals are still in the vicinity of, or are passing by, thefish farm several weeks after release. Although thereleased salmon move close to the surface for most ofthe time, diving is also observed. It was a clear tendencythat salmon dived to 20 to 50 metre depth immediatelyafter release. Repeated deep diving down to more than200 metre depth was also observed.

Tracing escaped farmed salmon by means ofnaturally occurring DNA markers, fatty acidprofiles, trace elements and stable isotopes- TRACESØystein Skaala, Bengt Finstad, Vidar Wennevik, Kevin Gloverand Bjørn Barlaup

In 2003, the Norwegian Ministry of Fisheries and CoastalAffairs took the initiative to set up a national committeeto explore available methods that could be used fortagging of farmed fish, in order to trace the origin ofescaped farmed salmon. The committee, withrepresentatives from the aquaculture industry, theresearch community and the management authorities,found that there were no methods ready forimplementation. It was concluded that two differentmethods of identifying escaped salmon should be


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investigated further: snout tagging (coded wire tags) and astand-by, contingency approach, based on naturallyoccurring characteristics of the fish. Based on theserecommendations, a project group led by Dr. ØysteinSkaala, Institute of Marine Research, with specialists ingenetics, chemistry and population biology, has been puttogether. A steering group, jointly led by the FisheriesDirectorate and the Directorate for Nature Management,was also put together. A project has been designed totest out the precision of methods that potentially can beused for tracing escaped salmon back to sea pen of origin.The focus is put on naturally occurring characteristics ofthe fish, and a stand-by contingency approach. Samples ofsalmon from all fish farms in the Hardangerfjord basin, andescaped farmed salmon, will be collected. DNA profiles,lipid acid profiles, trace element composition and stableisotope composition will be established, and the usefulnessof the various methods in tracing the sea pen of origin ofescaped salmon will be investigated.


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ANNEX 2Keynote Presentations -

Session Chairmen’s Summary



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Annex 2: Keynote Presentations- Session Chairmen’s SummaryLars Petter Hansen and Malcolm Windsor

Janne Sollie, the Director General of the Directorate forNature Management, opened the symposium andreminded us that while the topics on our programme thisweek were similar to those at the previous symposia heldin 1990 and 1997, the situation has changed. She referredto the significant growth of the industry since 1990 and tothe continuing decline in wild stocks despite majorreductions in fishing effort and a wide variety of measuresto address habitat issues in fresh water. She noted thatour understanding of interactions between cultured andwild salmon has increased markedly since 1990 and that itis now recognised that salmon farming can pose a seriousthreat to the wild stocks. However, she noted thatprogress is being made - there is now improvedcooperation between the salmon farming industry, theauthorities and various stakeholders. Furthermore, newmanagement measures designed to minimise impacts havebeen introduced, not least NASCO’s Oslo/WilliamsburgResolution. She noted, however, that we cannot afford tobe complacent and to highlight the importance of ourwork she referred to two very significant escapes offarmed salmon in Norway this year, which amounted toabout 600,000 fish. She concluded that additionalmeasures are still required and she stressed the need forsolutions to the challenges that remain, in order to movecloser towards sustainable culture of Atlantic salmon.

We were then reminded of the importance of the topicof this symposium to both NASCO and ICES. Therepresentative of ICES, Dr Niall Ó Maoiléidigh, told us thatthe subject of the symposium was highly relevant to theICES work programme and the President of NASCO, DrKen Whelan, challenged us to urgently find solutions tothe real problems that remain in managing interactionsbetween cultured and wild salmon.

We then had four excellent keynote presentations, whichset the scene for the week.

Pat O’Reilly highlighted, most eloquently, the social andeconomic values of the wild Atlantic salmon. In additionto the very significant values associated with the fisheriesand eco-tourism, he reminded us that the general publiccare about the wild Atlantic salmon, an indicator ofenvironmental well-being, and are prepared to pay verysubstantially to conserve it. He described, in militaryterms, the vulnerability of the resource - assault from the

air, land battles, attacks on freshwater habitat - andreferred to the progress being made on many fronts toaddress these problems through cooperation among theinterested parties. While many problems can be tackledat a national or local level, he stressed the need forinternational cooperation in addressing the problem ofsalmon survival at sea. With regard to salmon farming, hestressed the need for further progress on implementingNASCO’s Williamsburg Resolution to minimise impacts ofaquaculture, and the need to apply a PrecautionaryApproach. He noted that progress is being made, butcontainment is not adequate, given present levels offarmed production. This, he believed, was not in theindustry’s long-term interests, not least because thegenetic diversity present in the wild stocks is their futureseed-corn. However, he believed that enhancedcooperation between wild and farmed salmon interestscan address the remaining challenges. He cautioned thatwhile sound science can inform political decision-making,the real power lies with the general public. The messagewas clear : if the salmon farming industry was perceived tobe damaging the wild stocks, consumers may reject itsproducts. He concluded with a powerful rallying call to usall: Mother Nature has thrown down the gauntlet; wemust not wait until she has thrown in the towel.

Our second keynote speaker was Helge Midttun, whoreferred to the development of the salmon farmingindustry since the 1960s, an important source of incomefor coastal and other communities around the NorthAtlantic and elsewhere. Worldwide production in the lastdecade has trebled, reaching 1.2 million tonnes in 2004,and he considered that the continued success of theindustry will require that it is conducted in harmony withthe environment, and that where conflicts arise, the wayforward is through cooperation and planning. He referredto the fact that the world’s fish stocks are fully exploitedso aquaculture has a vital role to play in meeting futuredemand for seafood. He suggested that effluents ofnutrients and organic matter from salmon farming nolonger represent a major environmental problem, andantibiotic usage has been dramatically reduced. Heaccepted that while almost 98% of all farmed salmon arecontained in cages, the level of escapes is still too highrelative to the abundance of wild stocks. He stressed thatfor the salmon farming industry to continue its growth,the product must be perceived to be safe and healthy, itmust not be associated with any form of deterioration ofthe natural environment and the industry should be seento be open and transparent, and willing to focus on animalwelfare and environmentally sustainable practices.


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Walter Crozier picked up on Pat O’Reilly’s theme of thevulnerability of wild salmon stocks, presenting informationdeveloped by ICES which confirmed the depressed stateof salmon stocks around the North Atlantic. All fourEuropean stock complexes are considered by ICES to beoutside precautionary limits, and in North America 31%of monitored rivers are achieving less than 50% of theirconservation limits. Some stocks are critically endangered.Much has been achieved with regard to reducingexploitation, particularly in the distant-water fisheries, butmany factors are influencing the stocks. He stated thatwhile over-exploitation is not always part of the problem,exploitation control is often part of the solution torebuilding stocks. However, the modelled projections forstock rebuilding for low productivity stocks are very long-term. The message is clear ; given the status of thesestocks we must ensure that human activities do notexacerbate the situation.

Then Bror Jonsson presented an extremelycomprehensive review of the literature concerning theecology of cultured Atlantic salmon in nature and theirinteractions with wild fish. He concluded that hatcherysalmon compete for food, space and breeding partnerswith wild salmon in nature, and that their performanceand reproductive success, though variable, can be muchpoorer than that of wild fish. The reduced fitness is dueto a variety of changes, including morphological andphysiological changes which occur in the hatchery, someof which are short-term, others long-term. Hatchery fishin nature may partly displace, increase the mortality andreduce the growth rate of wild fish, with effects onassociated life-history traits, biomass and productionthrough density-dependent mechanisms. He highlightedthe need for further research on the factors influencingperformance of hatchery fish in nature and the ecosystemeffects of increasing salmon abundance in fresh and seawater.

James Ryan then reported to us on the TrondheimWorkshop, ‘Wild and Farmed Salmon - Working Together’,which had examined three themes: area managementinitiatives; the pros and cons of using sterile salmon infarming and restoration initiatives. He referred to possiblefuture initiatives that might be explored through theNASCO/salmon farming industry Liaison Group in thelight of the Workshop findings, including possibledevelopment of guidelines on area management initiativesand on restoration programmes, and he suggested thatthe use of sterile salmon be given further carefulconsideration by that Group.

Following the presentations we had an interestingdiscussion which focussed on aspects such as strayingrates and their implications for natural recolonisation ofrivers; approaches to stocking; the impacts of sea lice, amajor problem for the industry and for the wild stocks;and the possible consequences of climate change oninteractions between wild and cultured salmon, includingthose arising from increased frequency and severity ofstorms.

In summary then, a number of themes emerged from thisvaluable keynote session:

• Wild salmon stocks have enormous user and existence values. The general public cares about this most charismatic of fish species. Similarly, the salmon farming industry is an important source of income for coastal communities, whose success depends on its activities being conducted in harmony with the environment. The challenge is to find ways in which wild and farmed salmon can co-exist.

• Since the first symposium in 1990, our scientific understanding of interactions has increased considerably. It is even more clear that cultured salmon can have significant impacts on the wild stocks.While there is a need for additional research, under a Precautionary Approach this must not be used to delay further management action to minimise interactions.

• Despite the major sacrifices that have been made in reducing exploitation of wild salmon, and the progress made in protecting and restoring salmon habitat, and in introducing measures to minimise impacts of aquaculture, the abundance of wild stocks remains low, and in some cases critically low, for reasons we don’t fully understand. We must, therefore, ensure that our activities do not exacerbate the situation.

• If the salmon farming industry is to continue its growth it must be seen to be environmentally sustainable. Safeguarding the wild stocks is likely to bein the long-term interests of the industry. If it is perceived to have damaged the wild stocks there could well be a consumer backlash.

• While we have made real progress with regard to understanding and managing impacts of aquaculture soas to protect the wild stocks, and the industry has made significant progress, some big challenges remain,particularly with regard to further reducing escapes and in managing sea lice. It is clear that further


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progress can be made through a cooperative approach but we believe it has to have a greater sense of urgency.

• Climate change raises considerable uncertainty both about the prospects of rebuilding the wild stocks and the further development of the industry.

• There is not much time if we are to safeguard the future genetic diversity and abundance of the wild stocks. At the same time the demand for farmed fish continues to grow. So the task for the symposium is to urgently highlight the major challenges and identify possible solutions to these.


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ANNEX 3Genetic and Ecological Interactions and their Management -




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Annex 3: Genetic and EcologicalInteractions and theirManagement - SessionChairmen’s SummaryMary Colligan and Tom Cross

Introduction

The session entitled ‘Genetic and Ecological Interactionsand their Management’ contained a wide variety ofpresentations on observed interactions betweenaquaculture and wild stocks of Atlantic salmon and otherdiadromous fish species. Significant progress has beenmade since the 1997 symposium in Bath, England, atwhich time there was some evidence, but muchspeculation, about how wild and aquaculture stocks wouldinteract in the natural environment. Since the Bathsymposium there has been more experience with, andstudy of, interactions between wild and aquaculturesalmon. As these interactions have become moreprevalent, so has experience in methods for managingthese interactions. Presentations at the Bergensymposium provided evidence of managementexperiences, highlighting both successes and failures.

The Presentations

The first paper was presented by Kjetil Hindar andentitled ‘Genetic and ecological interactions between wildand cultured diadromous fish.’ New research since theBath symposium was highlighted, particularly experimentsin Norway and Ireland. The presentation identified anumber of modelled effects farm fish escapees can haveon wild fish. In some cases the population eventuallybecomes composed entirely of hybrids as the effects arecumulative over generations.

Experiences with aquaculture in Chile were presented byAlejandro Buschmann in a paper entitled ‘Interactionsbetween salmon farming and marine coastal ecosystemsin the south-east Pacific.’ The full environmental effects ofaquaculture in Chile are not known. However, thediversity in the benthic environment has beendocumented to have been reduced in the vicinity ofaquaculture cages. The abundance of predators was alsoobserved to be higher in areas with aquacultureinstallations. It was strongly recommended that the effectson native fish needed to be studied.

A presentation on the history of genetic research within

the aquaculture industry was presented by Arne Storset,entitled ‘Past, present, and future of genetic improvementin salmon farming.’ Individual and family selection methodswere reviewed. Molecular methods of selection wereidentified as likely to increase in importance in the future.It was emphasized that the goal within the Norwegianaquaculture industry was domestication.

Aina Valland’s presentation, ‘The causes and scale ofescapes from salmon farming,’ identified the followingcauses: technical failure, predators, floating objects andboat propellers. The relative contribution of each of thesecauses was found to vary significantly from year to year.The importance of internal control systems and educationand training to ensure staff competence were emphasized.

‘The escape of juvenile salmon from hatcheries intofreshwater streams in New Brunswick,’ presented byJonathan Carr, illustrated that escapes from freshwaterhatcheries can be a significant cause for concern. Escapedfish were recorded at the majority of hatcheries locatednear freshwater streams. A call was made forimplementation of containment strategies for freshwaterhatcheries.

Information on the behavior of escaped salmon waspresented by Fred Whoriskey in a paper entitled ‘Sonictracking of experimentally released farmed Atlantic salmonin the Cobscook Bay region, Maine.’ Escapes weresimulated in the winter and spring. Escapees were foundto disperse rapidly beyond 1km from the location of theirrelease. Many of the escapees were eliminated quickly inthe spring, possibly attributable to predation by seals.

Additional information on the behavior of escaped farmedsalmon was presented by Lars Petter Hansen in thepresentation ‘Migration and survival of farmed Atlanticsalmon released from two Norwegian fish farms.’ Theescaped fish did not appear to home to their release site.The survival and distribution of escapees depended onthe time of year of the escape and the release site. Muchof the distribution could be explained by currents.

Peder Fiske’s presentation, ‘The incidence of escapedfarmed salmon in relation to the extent of fish farmingactivity,’ found a positive correlation between the intensityof fish farming and the incidence of escapes. This studysuggests that the number of salmon in net pens is a betterindicator of farm escapees in rivers than the number ofreported escapees.

Alan Walker described the development of programmesto quantify the spatial and temporal distribution of


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escaped farmed Atlantic salmon in the UK and Ireland inthe presentation, ‘The development and results ofprogrammes to monitor the incidence of farm-originAtlantic salmon in rivers and fisheries of the British Isles.’The presentation assessed the implications of thepresence of escaped fish for the ongoing assessment andmanagement of wild stocks. Farmed fish can inflate catch-based spawning escapement and may increase the risk towild stocks. He suggested that one needs to look locallyat the stock specifics in order to determine what levels ofescapees are significant.

‘Using genetic markers to trace escaped salmon to farmof origin,’ presented by Vidar Wennevik, reviewed theresults of a pilot study investigating the possibility oftracing salmon to farm of origin using microsatellite DNAand genetic assignment tests. Although genetic methodsfor tagging are difficult, the point was made that thealternative of physical tagging can be very costly. Escapedfarmed salmon were able to be assigned with a highdegree of certainty to strain, which may be somewhatindicative of farm of origin. It was suggested that furtherwork should be undertaken to determine if precision canbe increased to provide enough information to assign anescapee to its farm of origin.

Harald Lura’s presentation, ‘Density-dependent spawningsuccess and contribution from farmed female Atlanticsalmon to wild populations,’ presented results from astudy on six rivers in Norway. The proportion ofsuccessful farmed spawners was found to be positivelycorrelated to the proportions of farmed fish in autumncatches and negatively correlated to the density of wildfish. Salmon domesticated for several generationscontributed to local populations, but were excluded athigh densities of wild fish, likely due to breedingcompetition.

‘Estimating impacts of salmon farming on salmonid survivalin the wild: a meta-analytic approach using populationdynamics data,’ was presented by Jennifer Ford. Thistheoretical model was used to estimate the impacts of seacage salmon farming on survival of wild salmonids usingpopulations less exposed as controls. This theoreticalmodel identified potential impacts of up to a 1%reduction in the productivity of wild fish for each tonne offarmed fish production, in the areas studied.

Øystein Skaala’s presentation, ‘Temporal genetic stability inAtlantic salmon populations,’ indicated that wild salmonpopulations in rivers with high numbers of farmedescapees became genetically more similar to each other

over time. While no genetic changes were observed insome rivers, changes were observed in rivers which havea higher proportion of farmed fish escapees. This workwas conducted using independent assignmentmethodology.

The ‘Pros and cons of using sterile salmon in aquaculture’were presented by Tillmann Benfey, who emphasized theimportance of assessing the need for sterile populationsand the full potential benefits and negative effects. Astrain that performs very well as a diploid may or may notbe a good performer as a triploid, so development of atriploid production strain requires an intentional breedingprogramme. Research on methods of sterility wereencouraged as well as full investigation of all of thepotential consequences, including effects on stressresistance and the immune system.

Arne Fredheim reviewed existing and potential new cagedesigns in his presentation, ‘Development in cagetechnology designed to minimize escapes from salmonfarms.’ The development in Norway of technicalrequirements for floating fish farms were reviewed as wellas the certification requirements for new farms. Apotential new cage design was presented that focuses onreducing the probability and consequence of accidentsboth with regard to technical failure and incidents, and toreducing the possibility and consequences of incorrect useand operation of equipment.

‘Conflicts between diadromous fish restorationprogrammes (e.g. shad, striped bass) and conservation ofpopulations of Atlantic salmon’ was presented by DouglasGrout. Information was presented on the efforts thatresulted in successful recovery of anadromous populationsof striped bass along the Atlantic coast of North America.The dramatic increase in striped bass abundance hasresulted in increased predation of a variety of speciesincluding American shad, river herring, and menhaden.

Kentaro Morita’s presentation, ‘A review of the Pacificsalmon hatchery programmes on Hokkaido Island, Japan,’illustrated the large-scale release of salmon to supportcommercial harvests. It was suggested that to usehatchery programmes more effectively we need toevaluate river- and species-specific net benefits fromhatchery programmes, and compare hatcheryprogrammes with other management tools, such as fisherycontrols and habitat rehabilitation. Adaptive learningapproaches should be utilized for hatchery programmesto minimize the risk associated with artificial propagationand to promote sustainable salmon stocks.


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‘Loss of regional population structure following stockenhancements in Atlantic salmon’ was presented byPaloma Moran. Significant genetic differentiation wasfound between neighboring rivers in Spain but was lost inonly a decade of stocking. Introgression of domesticatedgenomes into local gene pools was detected, showing thatlosing genetic diversity is a real threat for wild populationssubjected to enhancement activities.

Gorm Rasmussen’s presentation, ‘Estimates of strayingsalmon into rivers on the Swedish Kattegat west coastfrom coastal releases in the Baltic Sea,’ reviewed releasesof salmon from 1995-1999 from two Baltic strains. Somefish were reared and then released from netpens whileothers were released directly from the hatchery. Theprogramme was discontinued due to possible deleteriouseffects on the local wild salmon populations from strays.

‘Changes in wild and hatchery proportions of annualAtlantic salmon catches in the Baltic Sea’ was presentedby Marja-Liisa Koljonen. DNA level information from aneight-loci microsatellite baseline database of 32 Atlanticsalmon stocks was used with a Bayesian estimate methodto assess the stock and stock group proportions of Finnishcatches in the Baltic Sea area. The proportion of wildsalmon showed a rising trend until 2003 in all study areasas a result of higher mortality of hatchery fish than of wildfish.

Synthesis

As illustrated by the above brief summaries, this sessionincluded a great deal of information. An attempt wasmade to identify the key information across all thepresentations and to capture the key issues and pointsmade during the discussion period. This is summarizedbelow.

Escapees

The information presented indicated that escaped farmedfish dispersed quickly from the immediate vicinity of cages(>1km) and tended to move with dominant currents. Thefate and survival of escapees is highly variable and isaffected by a number of factors, including location ofescape, season of escape, age and maturity of theescapees and the presence of predators. Heavy sealpredation appeared to be experienced by fish escaping inthe spring in North America compared to those thatescaped in the winter. Fish that escape at an early stagefrom marine cages appear to attempt to return to the siteof their release.

Interactions

Compared to the Bath symposium in 1997, there appearsto be a decline in the number of escapees andimprovements in reporting. A positive correlation hasbeen observed between intensity of fish farming andincidence of escapees. The number of salmon in net pensis a better predictor of farm escapees in rivers/fisheriesthan the reported number of escapees. This couldindicate problems with reporting or perhaps indicate that‘trickle losses’, not observable to the fish farmer, are agreater source of escapees than previously thought.Escapes from freshwater facilities are not welldocumented and it is not known if this is an isolated orwidespread problem. Risks are posed by hatcheryprogrammes designed for intentional stocking as well asunintentional escapes from commercial culture operations.Goals of hatchery programmes need to be well thoughtout - they need to match the solution to the problem andevaluate effectiveness. All of the potential implications ofintentional releases need to be well thought out(Gyrodactylus salaris implications of Baltic salmon straysinto the Atlantic).

Genetic Interactions

Modelling evidence was presented that wild populationscan eventually become composed of hybrids due toaquaculture escapees. Genetic research by theaquaculture industry has resulted in a significant increasein growth of aquaculture fish (growth has been doubled ineight generations in Norway). Emerging molecularmethods provide opportunities for DNA fingerprintingand marker-assisted selection which would make selectionmore precise and cost-effective. It was stated that thegenetic approach in Norway now is to merge the fourgenetic lines and questions were raised as to whatimplications this could have for using genetics to identifyfarm source. The fact that genetic change has beenobserved in some rivers over time and not others isinfluenced by the numbers of farmed spawners anddensity of wild fish. This finding illustrates the importanceof looking at stock specifics to determine the level ofescapees that would be significant. It was demonstratedthat significant genetic differentiation can be reducedquickly due to stocking of non-native strains.

Ecological Interactions

Observed environmental effects from aquaculture facilitiesinclude algal blooms and a significant loss of benthicbiodiversity and diversity of other fish. Predation on


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native species was also found to increase as a result ofescapees predating on native species and an increase inmarine birds near farms. The use of a theoretical modelcomparing populations exposed to salmon farming tothose not exposed identified a reduction in productivecapacity of up to 1% per tonne of production in the areasstudied. An increase in predation on salmon as a result ofa successful restoration programme for anotheranadromous species emphasized the importance ofthinking of the entire ecosystem.

Management of Interactions

Increased reporting of escapees was identified as apositive development. Reporting of all escapees andcauses is required in Norway and other countries.Interactions between vessels and cages were identified asa significant cause of escapees and the simple solution ofrequiring radar reflectors and updating navigational chartswas identified. The National Action Plan in Norway isdesigned to prevent escapees (staff competence,information and education, environmental managementsystems). In addition, new certification requirements inNorway require capability assessments to ensure that theequipment at a farm is matched to the site conditions.Solutions to freshwater escapement may be inexpensiveand relatively easy (redundant screening).

One of the tools that has been identified for managementis better information on when, where, and how escapesoccur. Mandatory reporting is one source of suchinformation. If farmed fish were marked in a way toindicate farm of origin this could prove useful in beingable to trace escapees back to a farm to learn moreabout the cause of that escape. Using genetic markers,escaped farmed salmon may be assigned with a highdegree of certainty to strain (which may be somewhatindicative of farm of origin). Both biological and physicalmethods of containment were reviewed and discussed. Inconsidering triploidy, it was emphasized that it isimportant to be explicit about the purpose of sterility.Further research into cage design was encouraged and itwas suggested that cage design should focus on reducingthe probability and consequences of accidents as well asminimizing potential for incorrect use. Anothermanagement tool presented was the decision to move tonative strains for intentional enhancement programmes.

Recommendations for Future Research

Although much has been learned since the Bathsymposium, many more questions remain unanswered.

The following research needs were identified during thediscussion:

• Environmental effects of farming of salmon in Chile;

• Information on spawning success of escapees;

• NASCO and ICES have suggested a joint experiment to track escapees;

• Need further genetic work to determine if precision can be increased to provide enough information to assign an escapee to farm of origin;

• Pros and cons of triploids warrants further investigation and discussion - effects on immunity,stress response;

• Development of a high-performing triploid strain requires a deliberate selective process.

Recommendations and Challenges for Management

The fact that the causes of escapees are diverse andhighly variable on an annual basis (technical difficulties,boat propellers, predators, floating objects) means thatthere must be multiple management actions targetingthese various sources. The question was raised as towhether management should change seasonally and/ordepending on age of fish in recognition of the anticipateddifferences in survival of the escapees. Storms wereidentified as major source of escapees and the questionwas raised as to whether climate change would increasestorm events and lead to more escapees. The aquacultureindustry appears to be moving toward larger and largercages which pose significant management challenges asthe loss of one of these cages could release more fishthan an entire site using older, smaller cages. Also, sitesare moving further away from salmon rivers and to moreexposed areas which may also increase their vulnerabilityto storms. Managers were cautioned to consider theeffects of farmed fish on catch advice as they can inflatecatch-based spawning escapement (which may increaserisk to wild fish). There was a strong emphasis on theapplication of an ecosystem approach to fully understandall of the effects of aquaculture.


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ANNEX 4Disease and Parasite Interactions and their Management -


The River Drammen, Norway where stocking is being used to mitigate losses caused by the parasiteGyrodactylus salaris.


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Annex 4: Disease and ParasiteIinteractions and theirManagement - SessionChairmen’s SummaryMalcolm Beveridge and Chris Poupard

Fifteen papers on the two broad themes of science andmanagement of disease and parasite interactions werepresented, none of them considering species other thanAtlantic salmon and sea trout.

Ron Stagg opened the session with a broad-rangingpresentation that dealt with micro- and macro-parasites, inessence covering the entire gamut of Atlantic salmondisease agents, from viruses and bacteria to ectoparasites.The paper examined some of the more importantdiseases that have appeared in salmon farms in Scotlandsince the inception of the industry and in so doingconcluded that while originating in wild populations, theemergence of parasitic infestations among farmed fish,sometimes with increasing associated virulence, is aninevitable consequence of farming. Much of thepresentation focused on epidemics, exploring the insightsbeing gained through the use of new types ofmathematical modelling tools. The paper pointed out thekey differences between micro- and macro-parasiteepidemics. It concluded that epidemics among farmedpopulations do not necessarily result in epidemics amongwild fish populations, stressing the importance of goodbio-security and husbandry in mitigating risk.

Sea lice, and Lepeophtheirus salmonis rather than Caliguselongatus, were mentioned in Ron Stagg’s presentation andindeed dominated much of the rest of the day’spresentations and discussions. Karin Boxaspen reviewedwhat we know about the biology and genetics of theparasite, focusing on recent research on life history,especially the impacts of temperature and salinity ondevelopmental rates, on behaviour and dispersion. Shereviewed new information on natural distribution andadvances in the application of genetic techniques tounderstand parasite population structure and geneticdiversity. The new discoveries are being applied to refinepest management strategies and to assess risks to wild fishpopulations. Molecular genetics work raises the possibilityof a vaccine being developed against the parasite.

A series of presentations explored the theme of wild-farmed fish pathogen interactions. Neil Hazon reported

on how sea lice infestation affected the physiology of wildsea trout. In a series of laboratory trials, the thresholdlevels of infestation at which physiological stress andosmoregulatory problems occur were determined. Athreshold level of infestation at which mortality among seatrout smolts was likely to occur was determined to be 13lice per fish. The susceptibility of wild, farmed and wild-farmed hybrid Atlantic salmon to sea lice and to InfectiousSalmon Anaemia (ISA) and furunculosis was explored byKevin Glover. No differences among fish treatmentgroups were found for furunculosis or ISA, and thedifferences apparent in exposure to sea lice disappearedwhen differences in body size among treatment groupswere taken into account. In conclusion, whiledomestication to date does not seem to have led to anysystematic divergence in disease resistance from wildsalmon, future selection programmes may.

The paper presented by Bengt Finstad summarizedpresent knowledge of interactions between lice onfarmed and wild salmonids, drawing on much monitoringdata from Scotland, Ireland and Norway. Key points fromthe presentation included the high infection pressureimposed by farms on wild stocks in many areas and theinverse relationships between incidence of lice on wild seatrout and distance from fish farms.

In determining the infection pressures that sea lice onfarmed fish pose for wild salmonids it is important tounderstand sea lice dispersal and the behaviour of wildsalmonids that makes them susceptible to infestation. Twopapers provided us with insights. Michael Penstonpresented two years of plankton survey data from LochShieldaig in Northwest Scotland. Higher nauplii densitieswere found at sample sites close to farms whilecopepodid levels were highest at sites away from farms.Dispersal of copepodids was shown to be largelyexplained by wind-driven currents; by contrast, naupliiwere found throughout the top 5 m. GeneralisedAdditive Models were used to analyse the pattern ofplanktonic lice abundance, which showed an increase fromstocking of farmed fish throughout the production cycle,followed by a marked decrease when fallowing beganagain.

Peter Andreas Heuch looked at the effects of bothhydrography and infection pressure on infection rate ofAtlantic salmon and sea trout smolts emigrating from thetwo contrasting fjord systems. These studies illustratednot only differences between areas in terms of infectionpressure, but also that within a system year-to-year


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differences in hydrography could cause changes in sea licedispersion that radically altered risks to wild fish.Differences between emerging dispersion models inNorway and Scotland were briefly discussed.

Ron Stagg had posed the question of whether anyone haddetermined the impacts of sea lice on wild fishpopulations. Bengt Finstad attributed this to the lack ofsystematic investigation, a deficiency currently beingaddressed through the collaborative research project withindustry, recently initiated in the Hardangerfjord system.

Tom Cross also appeared to have anticipated the questionof impacts of sea lice on wild fish populations butexplored qualitative changes at the genotype andphenotype level rather than numerical changes. Theyexamined impacts of diseases associated with farming ongenetic variability of sea trout from two systems, the Erriffand the Burrishoole. Archived scale samples wereexamined and variations at both a locus critical toimmune response (MHC1) and six neutral microsatelliteloci were measured. Two contrasting situations werefound: in the Erriff, decreases in genetic variability werefound in both MHC1 and the neutral markers. Bycontrast, later samples from the Burrishoole showed arecovery in MHC1 variability. Evidence was presented toshow differences between the two systems in the relativeproportions of sea trout to freshwater-resident fish, withproportionally much higher numbers of freshwater-resident trout in the Burrishoole.

Chrys-Ellen Neville presented a paper on the effects offish farm lice on wild pink salmon. Large numbers of pinksalmon smolts emigrate through the Queen CharlotteStrait, an area of intense Atlantic salmon farming activity.Data from a recent year class was presented, showing thatadult pink salmon returned in unusually high numbers thefollowing year but it was not possible to concludewhether this was due to the Provincial Action Plan whichintroduced a fallowed migration corridor, or increasedfreshwater flow, which could lead to conditions lessfavourable to sea lice production, or other factors.

Another session theme was sea lice control. Currenthealth management practices on Scottish salmon farmswere discussed by Graeme Dear. Bacterial problemswere shown to be largely under control due to vaccines,resulting in major reductions in the use of antibacterialcompounds. Viral diseases remained a serious concern,recent ISA outbreaks having largely been controlled onlythrough rigorous culling. Management measures, incombination with access to good medicines, have been

critical in reducing sea lice levels on farms, although moreeffort is required by some sectors of the industry. A keymessage was the threat posed by the emergence of newdisease challenges, but also flagged up were the potentialof genetic selection to improve disease resistance, theemerging field of nutraceuticals, and the continuedimportance of application of best practice to avoiddisease.

Trends in the use of medicines in the Norwegian salmonfarming industry were presented by Kari Grave. Thispresentation focused on the question of whether thecurrent use of antimicrobials and anti-sea lice medicines inparticular posed any threat to wild fish. While it wasconcluded that there were no toxicological risks, sub-optimal treatments against sea lice promoted heavy liceinfestations and increased infection pressure on emigratingAtlantic salmon smolts. At the opposite extreme, over-reliance on certain key medicines increased the risk ofdevelopment of resistance with consequent welfareconcerns and increased risks to wild fish. Ove Skilbreiassessed whether treatment of ranched Atlantic salmonagainst sea lice with orally administered emamectinbenzoate prior to release affected survival. Survival didnot differ between treatment and control groups releasedin May, but there was a two-fold increase in survival intreated compared with untreated fish released in June.Moreover, treated fish were almost one third heavier. Itwas also concluded that sub-lethal lice levels may affectgrowth and, therefore, size at spawning and fecundity ofwild fish.

The use of cleaner wrasse to control sea lice on farmedfish was reviewed by Per Gunnar Kvenseth. Thepresentation informed the audience of the efficacy andcost-effectiveness of using wrasse to control sea lice incommercial farm situations and the recent advances inbreeding of ballan wrasse in particular. He concluded thatwrasse should be considered as part of an integrated sealice management strategy.

Data sharing, trust and cooperation among regulators,farmers and wild fish interests are the foundationsessential to any effective management control strategy.The achievements of the Scottish Tripartite WorkingGroup approach to this were reviewed by Phil Gilmour.Organisational aspects at national, regional and local levelswere explained. Success was judged in terms of thedegree of consensus that had been achieved, the numberof Area Management Groups that had been formed andArea Management Agreements that had been signed.


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While it had proved difficult to draw conclusions aboutthe beneficial effects on wild fish populations, it wasagreed that the approach had transformedcommunications among parties, provided value for moneyand represented the way forward for the future.

Finally, there was a single paper on Gyrodactylus salaris,presented by Jarle Steinkjer. The introduction and spreadof the disease to 45 salmon rivers in Norway wasdocumented. The key features of the Norwegian actionplan were presented: surveillance, prevention, eradicationand restoration. To date, 27 of the 45 infected rivers hadbeen successfully treated, with plans to treat a further fourin the next year. The growing use of acidified aluminiumas a treatment method, which unlike rotenone kills onlythe parasite and not the fish, was discussed. The dangersposed by fish movements, especially of rainbow trout, andthe importance of international cooperation to stop thefurther spread of the parasite were highlighted. Despitebeing the sole paper considering the problem, itstimulated much debate.

SynthesisThe introductory overview provided some context inwhich disease and parasite interactions might be viewedand provided warnings and some comfort as to whatmight be expected with regard to the emergence of newdiseases in aquaculture and the implications for bothfarmed and wild fish. This and the presentation onGyrodactylus salaris aside, the session on disease andparasite interactions and their management proved to bevery much concerned with sea lice and Atlantic salmon.

It was apparent that much more is now known about allaspects of sea lice biology than at the Bath symposium in1997. The focus at the present meeting on the moreproblematic Lepeophtheirus salmonis at the expense,perhaps, of finding out more about Caligus elongatus,reflects the situation in the scientific research community:a quick scan of the literature shows there to have beensomething like six times more publications on L. salmonisthan C. elongatus in the past eight years. It is clear that wenow have a much better understanding of fecundity andits regulation, hatching and larval development, the role oftemperature in determining infection success, mortality atvarious life stages, dispersal and the role of behaviour. Allof this has led to better tools for identification of sea liceand is enabling the development of increasingly effectiveintegrated pest management strategies and still holds outthe hope of an effective vaccine being developed.

Monitoring data from various countries were reviewed,demonstrating once again that infection pressure posed byfish farms remains an important issue in many areas. It isnow clear that lice abundance tends to change in a fairlypredictable manner during the farm production cycle andthat this knowledge can be used to help manage licenumbers. By virtue of their behaviour sea trout are highlysusceptible to sea lice infestation, susceptibility decreasingwith distance from farms. New studies in Norway,however, clearly show that infestation levels on emigratingAtlantic salmon smolts are highly site-dependent and thatrisk of infestation also varies from year to year with tidalconditions, wind strengths, etc. Since the Bath symposiumthere have been a number of important, EC-fundedinternational projects that have provided muchinformation about the effects of sea lice on fish physiologyand osmoregulation in particular. For both Atlanticsalmon and sea trout, lice burden is now recognised as astrong predictor of mortality; for sea trout smolts, forexample, the number 13 has more than just superstitiousconnotations. That we may not yet fully understand risk,however, is evident from the Canadian study, whichshowed that the links between infection pressure, liceburdens and mortality rates among migratory pink salmonto be perhaps less than straightforward. On-goingprojects in Scotland and Norway are likely to bear fruit interms of our abilities to assess effects of sea lice on wildfish at the population level. While it might have beensuspected that prolonged, elevated mortality rates on seatrout might affect selection for migratory behaviour, thework at Burrishoole in Ireland clearly demonstrates this.

Sea lice management has evolved considerably in the pasteight years thanks to increased knowledge and to greatlyimproved management. The effectiveness of the ScottishArea Management Agreement regime in terms of datasharing to improve lice control clearly provides muchencouragement. Nevertheless, concerns were also clearlyexpressed about the heavy reliance on a handful of keymedicines and, from some quarters, about the increasingsize of farms from a disease management point of view aswell as in terms of escapes. Perhaps wrasse, still popularin Norway but abandoned elsewhere for various reasons,should be reconsidered as an important option in anyIntegrated Pest Management regime. Finally, while thereare signs of improvement, sea lice remain a majorchallenge to all interested in sea trout and Atlantic salmon.


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ANNEX 5Poster Session - Session Chairmen’s Summary



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Annex 5: Poster Session -Session Chairmen’s SummaryArni Isaksson and Peter Hutchinson

The poster session comprised a total of 13 presentationsfrom 8 countries. The subjects covered in ten of theposters can be roughly grouped into three main topicareas: (1) studies on the abundance, distribution, behaviourand source of escapees (5 papers); (2) genetic aspects ofstocking programmes (3 papers); and (3) sea lice biology(2 papers). There were also papers on aquaculture-freezones, the feeding behaviour of cultured and wild salmonsmolts and on the effects of domestication.

Escapees

A study in the River Teno, also called Tana, a border riverbetween Norway and Finland, presented the results ofsampling for escapees during and after the fishing season.The results indicated that escapees were widelydistributed in this river but made up a small proportion ofthe catch during the fishing season. However, in somesmall samples taken, after the season they accounted forup to 47% of the fish sampled. As there is highlysignificant genetic differentiation between wild andescaped farmed salmon and the escapees have highpotential for successful reproduction, there is concernabout the impacts on the native salmon populations

In a study from Norway, catch data from gill nets set bylocal fishermen to target escaped farmed salmonids wereused to estimate abundance of escapees and to classifythe fish into different escapement events on the basis ofcatch-per-unit effort. It concluded that most of theescapees were of local origin. The study indicated that itwas possible to reduce the abundance of rainbow troutescapees by fishing during a 2 - 4 week period and thepaper concluded that an autumn fishery may be a usefulmanagement tool, by identifying escape events, includingunreported ones, and stimulating escapee recaptureefforts.

A second study from Norway involving acoustic tagging offarmed salmon ‘escapees’ showed that several of thetagged individuals were still in the vicinity of the escapesite after several weeks, suggesting that it may be possibleto recapture escapees. The results from this study aresomewhat different to experience in the Bay of Fundy,Canada, where most experimental ‘escapees’ seemed tomove away from the site of release quickly.

The Norwegian Parliament has decided that approaches

to tagging farmed salmon should be considered. Of themany potential methods, two approaches wereconsidered to have potential - coded wire tags and anapproach to identify to farm of origin on the basis ofnaturally-occurring characteristics of the fish. A study hasbeen initiated in the Hardangerfjord, the ‘TRACES’ project,to examine the costs and time efficiency of identifying andtracing sea pen origin of escapees by means of DNAmicrosatellite markers, single nucleotide polymorphisms,fatty acid profiles, trace elements and stable isotopes. Theproject will continue in 2006 subject to funding beingsecured.

Perhaps somewhat surprisingly for a symposium ondiadromous fish, there was a poster on acoustic trackingof cod in the Bay of Fundy. There have been suggestionsthat diversification of aquaculture from salmon into otherspecies of fish may offer benefits in minimising impacts onwild salmon stocks. This paper, however, reported thattracked wild cod, known predators of salmon, were foundin the exit corridors of wild smolts. The concern is thatescapees from cod farming, if they behave like the trackedwild cod in this study and concentrate in smolt migrationcorridors, could prey on wild salmon smolts.

Genetic aspects of stocking programmes

While the focus of much of this symposium has been onsalmon farming, the second group of posters waspredominantly concerned with the genetic aspects ofstocking programmes. In southern European rivers,salmon were often stocked from northern Europeancountries in response to declining native populations.Since 1995, the stocking programmes in the rivers Ullaand Lérez in Spain have only released descendants ofnaturally returning adults and of wild parr. The success ofthis programme is being monitored using physical markersand appears satisfactory. A study was conducted usinghistorical scale samples to investigate genetic variationbefore and after the stocking. This study showed thatmodern populations are very similar genetically to thosepresent prior to stocking, and there are still geneticdifferences between the two rivers, suggesting localadaptation and low straying rates.

Historical scale samples were also used to evaluate thedegree and direction of the genetic changes which haveoccurred in the stocks introduced to the ConnecticutRiver in the USA as a part of a major restorationprogramme. The current genetic profile of theConnecticut River stock is very similar to that of its donorpopulation in the Penobscot River, although there have


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been some differences for both sea run age and allelefrequencies. The effective number of breeders in bothrivers was large enough to preserve genetic variability.

The third study analysed stock and recruitment data fromthe Burrishoole system in Ireland, which has receivedvariable but significant quantities of naturally spawningranched hatchery fish founded from the wild populationsover a 35-year period. The results suggest that thesehatchery fish had a significant depressive impact on therecipient population and that removal rather than additionof these hatchery fish may be the most effective strategyto enhance wild stocks. Indeed, this approach is beingfollowed and there has been a significant improvement infreshwater production of salmon smolts. However, theauthors believe that common garden experiments areneeded to better understand the mechanisms involved.

Sea lice

The third group of posters looked at sea lice issues andthere were two presentations. The first examinedinfestation success of sea lice at different temperaturesranging from 6 - 14°C and found that lice were infectiousfor a longer period of time at low temperatures, up to 30days for one individual at 6°C. These data are importantfor modelling the dispersal and survival of free-living licelarvae.

The second paper examined the role of freshwateracidification on sensitivity of smolts to sea lice andconcluded that the combined effects of acidification andmoderate sea lice infestation can have the same negativeeffect as higher acidification or higher sea lice densities.The concern here is that where multiple stressors occur,focusing only on the impacts of a single stressor mayconsiderably underestimate the significance of theproblem.

Aquaculture-free zones

One approach to protect wild salmon stocks fromescapees, and possibly other adverse impacts fromaquaculture, is the establishment of aquaculture-freezones. A poster from Iceland described the establishmentof such zones in all wild-salmon-producing areas as aprecautionary measure. This was deemed necessary toprotect the valuable salmon angling fisheries in Iceland.

Behaviour of wild and cultured parr

A study conducted in Russia compared the feedingbehaviour of stocked and wild salmon smolts by divingobservations in the wild. While the cultured and wild

smolts had generally similar diets and feeding behaviours,there were some differences. For example, culturedsalmon were less able to differentiate food items fromnon-food items than wild fish and were more aggressive.

Domestication effects

A comparison was made of the growth, behaviour andphysiology of fast-growing (domesticated), slow-growing(non-selected), and hybrid strains of coho salmon andrainbow trout. Under all rearing environments, there wasa strong correlation between growth and the proportionof domestic genes within the genotype. Comparisons ofanti-predator behaviour and hormone profiles illustratedsimilar trends. The authors concluded that knowledge ofthe genetic changes responsible for altered growth ratesin fish is crucial information needed to increase our abilityto predict the consequences of introgression betweenfast- and slow-growing strains of fish.


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ANNEX 6Take-Home Messages

The City of Bergen.


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Annex 6:Take-Home Messages1. Katherine Bostick• Many thanks to NASCO and ICES for organizing this

symposium. A wealth of information has been presented here.

• I come to this meeting with a background relating to the global environmental and social impacts of aquaculture and of the global salmon farming industry in particular. Due to my relatively limited knowledge of wild Atlantic salmon, I have a different perspective than many of the individuals at this symposium.

• I am struck by a common theme of variability in and among the findings presented here, and how results are often situation-specific.The behavior of escapes varies from region to region - how quickly they move away from the farms, or not. Survival and spawning ofescaped or released Atlantics can depend on time of year and age. A disease epidemic on a farm can become an epidemic in the wild, but that depends on a number of variables.

• Given this variability, there is a common temptation tocontinue to do more research. But we cannot get lostin this. Symposia such as this one allow us the opportunity to take a step back and look at the big picture, identify trends, and consider how to apply lessons learned from one specific location or experiment to another.

• From my experience, the extent to which the salmon aquaculture industry acknowledges impacts and attempts to reduce them is highly variable as well - among countries, companies, and down to specific farms.

• One presenter mentioned that the industry does not need to wait until there is statistically significant evidence of harm being done in order for them to take action. The example of Norwegian industry and sea lice was given. What I have seen here relating to restoration and restocking efforts and the challenges that they present make it clear to me that the industryneed not wait, but also that we cannot afford to have them wait, or it will be too late.

• On a more specific note, the issue of escapes has been a large one at this symposium. There needs to be clear penalties for companies when escapes occur.Yes, there are real costs to producers when fish escape. However, there must be a cost on top of the

cost of fish lost. I’ve heard mention of the deliberate release of non-performers from farms - when an age-group is changed to a larger meshed cage, the slowest-growing fish can escape, and the farm does not then have to continue to put in feed for these non-performers. If this happens, it is completely unacceptable. There needs to be enforcement and penalties. Tagging, genetic or physical, was discussed here as a possible means to determine the farm of origin of escapees.

• Sea lice has been another area of focus at this symposium. Presentations here have shown that sea lice have a clear negative impact on wild salmon (mortality and decreased growth), and that in Norway,management of farms can reduce this impact. We have seen that in Canada, the same species of lice are found on farmed Atlantics and wild Pacifics. In Chile,another species of sea louse is found on farmed fish.While we heard evidence that pink salmon runs are healthy, I strongly urge governments and industry in these countries not to overlook the lessons learned from the Norwegian situation and to follow a precautionary principle approach.

• A number of the presentations here have been authored by international groups - and scientists continuing to collaborate in this way is one excellent method for sharing knowledge across borders, and hopefully, allowing us all to learn from each other. I encourage researchers to continue to reach across borders in this way.

It is clear that there is much work to be done in thefuture to address the issues that have come up over thepast few days. We look forward to working withNASCO, ICES, and the individuals present here to worktowards solutions. I believe that there are roles forgovernments, industry, NGOs, and other stakeholders towork with scientists to help ensure that wild and farmedsalmon can co-exist.

2. Fiona CameronDuring this symposium, I have heard an impressiveamount of evidence reinforcing the threat to wild fishrepresented by escapes from salmon farms - particularlyin situations where wild stocks are severely depleted - andby sea lice infestation, which seriously affects the marinesurvival of wild salmonids. I believe that we now haveconclusive evidence of these threats. There has beenmuch emphasis on the need to adopt the precautionary


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principle.

I heard some spokespeople for the salmon farming sectoraccept that these problems exist, that the industry isworking hard to fix them, and that we need consensusand co-operation to meet the challenges, particularly astonnage of farmed salmon increases and we see ongoingdevelopment of resistance to sea lice medicines.

But I also heard some hints - as one does in other fora -that there are still some people within the industry whoappear to be in denial about the seriousness of theseimpacts on wild fish.

At the NASCO workshop in Trondheim this August, NellHalse referred to the fish farming industry’s ‘justifiableparanoia’. I believe there are people on the wild fish andenvironmental side who are also guilty of ‘justifiableparanoia’. We need to get rid of the culture of blame andlook together at the multiple impacts on wild stocks, toidentify what we can tackle.

A strong message I take away from this symposium is thatwe’d better address this sooner rather than later because,as Pat O’Reilly reminded us, many stocks of wild salmondon’t have the luxury of time on their side.

We heard that we need to recognise what we can workto change - and I believe that applies to the wild fishsector too. Where there are multiple effects, it’snecessary to work co-operatively on the ones we havethe power to address.

It’s clear that regulation has a role to play, in both sea licemanagement and minimisation of escapes. It’s a counselof perfection that this should be backed up by local andregional co-operation. I sense that there’s a lot of interestin this, and perhaps a message for NASCO to take awayis that it could facilitate some ‘cherry-picking’ sessions toarrive at some sort of guidelines for area management,based on what works and what doesn’t?

I have learned - both in the presentations and in coffee-break conversations with other delegates - that in orderto be effective, area management needs to get better atengaging communities as well as a wide range ofstakeholders. It has to be inclusive, transparent, with abuilt-in way of measuring success - I’d probably add that ithas to be accountable. Both ‘sides’ have to communicate -particularly in view of what we’ve heard about thescenario of emergent resistance to sea lice medicines, andthe importance of spotting early signs of fish disease.

The challenge is: how do we report successes which may

not be easily measurable, to boost public confidence andstakeholder buy-in?

From what I’ve heard here, it seems to me that the mostcrucial requirement is good - top-notch - communication.I believe that we have to go beyond that, because‘communication’ can be one-way, particularly governmentcommunication. We need more constructive dialogue andcooperation, and trust.

Malcolm mentioned at the start that he’s convinced wecan have ‘win-win’. I’m leaving this gathering still with asense of optimism that we can achieve that - but only ifwe can do away with confrontation, which is seldomconstructive. We need to stop the tug-of-war and put allhands to the rope to pull in the same direction to meetthe challenges.

I don’t think we need any more evidence to prove thatthere are problems; we need to take that as a given andmove on to find cooperative and pragmatic ways ofaddressing these problems. We need to see the wild fishside and the industry playing on the same team andseeking out the common ground.

The worst outcome would be another NASCO meetingin several years’ time where we still hear mountingevidence of problems. The next one needs to be arecord of the solutions that are being explored!

3. Knut A. HjeltDuring the last three days we have had a number ofpresentations focusing mainly on the possible interactionbetween aquaculture and wild stocks of Atlantic salmon.The symposium has shown us that today we have muchmore science-based information about possibleinteractions between aquaculture and wild fish thanbefore.

The industry is still young, but over the years it hasevolved tremendously, and will continue to evolve in thefuture. As we have heard, the industry has put a lot ofeffort into preventing possible negative interactions withthe wild stocks. The focus has been on health, technicalimprovements, codes of best practice, site selection andgood training and management. The production ofAtlantic salmon is mainly based in areas where the wildAtlantic salmon is most abundant, which in itself is achallenge. But populations of Atlantic salmon are facing avariety of possible threats, and attention must be paid toall kinds of negative interactions, not only the topicsconsidered during this symposium.


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All kinds of food production, including aquaculture, willhave some impact on the environment. The challenge isto minimize such impacts in a way that ensures that wildand farmed salmon can co-exist, and more widely for allsalmon production around the world to ensure that thelevel of interaction with the environment is acceptable.

Having been here for three days, listening to thepresentations and discussions, my opinion is that the mainchallenge for the industry is to minimize the number ofescapees. This will most probably also have positiveinfluences on other areas of concern.

The industry has achieved quite a lot in this area, butthere is room for improvement. I will therefore brieflycomment on three areas which need to be addressed.

Land-based facilities

It should be possible to eliminate almost entirely escapeesand leakage from hatcheries and fry and smolt productionsites. There is probably not very much science in this, butrather it involves refinement of technology, risk assessmentand focus on risk awareness.

Sea-based facilities

There is a tendency towards larger units in more exposedareas when it comes to on-growing sites. The industryhas taken a wide range of measures to reduce the risk ofaccidents, but even if the number of escape incidents isdeclining, the size and effect of each incident could belarger. One requirement is to be very focused onminimizing the probability of escapes occurring, andtechnology, moorings, nets, site selection and equipmentare key words in this context. Further R&D on escapeprevention, and also giving increasing focus to possibleways to minimize damage when accidents occur, isimportant. The industry is looking for practical and cost-effective solutions. Attention should also be paid to otherpossible solutions to cost-effective production andoperation.

Trickle losses

An important challenge is to minimize the so called ‘tricklelosses;’ i.e. the leakages of fish that are not being detected.R&D, surveillance, risk assessment and awareness will beof importance in solving the problem. The problemshould be addressed at all life-stages, with special focus onwhat happens around times were fish are being moved,handled or put to sea.

The industry has escapees as one of their main focuses.We are cooperative and transparent; we do see the

problems and are working continuously towardsimprovements. This happens through voluntarily actionand through fulfilment of regulations. Obligatory actionsare probably needed in some cases. Together with thekey words, cooperation, regulation, third party inspectionsand reactions, R&D and cost-effective solutions will be ofimportance. Aquaculture will in the future, as today, be animportant part of international food production. As such,the salmon farming industry relies on being regarded asresponsible and with a high degree of credibility. This isthe case today, and it must also be so in the future.Addressing the challenge of minimizing escapees will be apart of this.

4. Jens Christian HolmFirst of all - Conveners and members of the SteeringCommittee - congratulations to you - this has been aninteresting symposium dealing with some very seriousquestions.

For me - representing the regulation side of aquaculturein Norway - a lot of the messages from this symposium(both questions and results) relate to the increasing size ofour salmon industry. Industrialising a biological processvery often means increasing the size scale.

Size matters. The number of salmon in one large farmcan be higher than the total number of wild Atlanticsalmon present in the sea originating from all Norway’ssalmon-producing rivers. The maximum biomass allowedin Norway’s 864 licences for commercial on-growing ofAtlantic salmon, trout and rainbow trout, is approximately690,000 metric tonnes.

Net pen size, farm size and the number of farmed fish inmost regions have increased in our aquaculture industry inrecent years.

Larger netpens can result in larger numbers of escapees ifthe pen is destroyed. A larger group of farmed salmon ishard to manage if the technology and operationalprocedures used are not adjusted. Medical treatment isnot easy in super-large units; obtaining therapeutic dosagefor all individuals by oral administration will be almostimpossible and resistance may be the result.

Larger farms holding higher numbers of fish in a small areawill generally increase the risk of disease. And if a seriousdisease outbreak occurs, the number of mortalities can beso high that neither the fishfarmer nor society have anadequate infrastructure to tackle it. And sometimes awhole fish farm might collapse in extreme rough weatheror if a ship collides with it.


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We have to deal more with the matter of size in futureregulations. Research, industry and public authorities haveto continue the good work together at arenas like thissymposium - so that we can avoid being outmanoeuveredby the law of large numbers.

I would like to acknowledge the excellent work carriedout in the Hardangerfjord area. The outstanding resultswith regard to salmon lice will hopefully be matched withregard to the escapement problem. The secret: focusedresearch, communication and coordination.

We must all work hard to minimise the negative aspectsof fish farming with a faster tempo than the growth rateof the salmon farming industry. The risk of escape persalmon in captivity should be reduced more than theincrease in numbers reared in captivity, in order to reducethe number of escapees. The reduction in the number ofgravid salmon lice per fish in a farm should exceed theincrease in the number of hosts in captivity so that theinfestation pressure on wild Atlantic salmon nearby isreduced. We must start to discuss such principles if weare going to share the common resources - the Atlanticsalmon and the areas it lives in - in a sustainable way.

5. James RyanPat O’Reilly reminded us that the salmon has beenevolving for 100 million years. Salmon farmers are keenlyaware of the inestimable value of the salmon resourceand they are just as intrigued by the sight of a wild salmonin nature as the most avid angler. Many times on mysalmon farm I have seen all work stop so that we couldwatch wild salmon running up the bay towards theestuary. And no, they were not escapees!

I attended the Bath symposium in 1997 and I believe wehave come a long way since then. At Bath a lot less wasknown about the facts of interactions and this left toomuch room for speculation. I think most people left thatsymposium more confused than when they arrived.Whereas in Bergen this week, we have been presentedwith the results of a lot of good research into the realeffects of salmon aquaculture on wild salmon and into themitigation of those effects. Salmon farmers can no longerclaim that aquaculture poses no threat to wild salmon butcan also point to a lot of scientific work whichdemonstrates that good management of farms ensuresthat the two sectors can live together in harmony.

In Bergen I have received both good news and bad news.First the bad news.

Escapees can breed with wild stocks and cause reduced

genetic diversity and reduced fitness for survival. Thismeans that farms must do more to ensure that escapesdo not occur. It also appears from research presentedthat the use of triploid farm stocks will likely not be themagic bullet many people had hoped for. We were toldthat trials with triploid stocks indicate that these fish aremore difficult to rear than diploids and should really betreated like a new species. It was suggested that triploidswould need many generations of selective breedingbefore they could equal diploids in their suitability forhusbandry. It is a particular concern of the industry thatno salmon farming country should be commerciallydisadvantaged vis-à-vis the rest of the world by beingcompelled to use inferior triploid stocks.

On the question of lice we have to accept that in certainsituations salmon farms can magnify the lice risk for wildsalmon. In these cases farmers will need to modify theirmanagement practices.

And now for the good news.

Improving Farm Management

There is a global trend of improving managementpractices on farms so that threats to wild stocks are beingreduced. Peder Fiske informed us that there are statisticalindications of better containment on Norwegian farmsand Aina Valland presented figures which demonstratedthat ‘routine’ escapes in Norway are significantly reduced,though there remains a problem with catastrophes suchas a whole farm being wiped out in a storm and shippingcolliding with cages. She indicated that new strategies arebeing adopted to help eliminate these one-off events. Wewere told that escapee numbers in indicator rivers inNew Brunswick had fallen by 90% over the last 10 yearsand that in Ireland and Scotland escapees constituted lessthan 2% and less than 5%, respectively, of coastal salmonstocks.

In situations where it had been shown that farms wereincreasing the lice risk for wild salmon it wasdemonstrated, with examples from both Norway andScotland, that farm management practices such as areafallowing and synchronised treatments could eliminate thefarm portion of that risk. In this regard the AreaManagement approach used in Scotland is payingdividends and could be a model for other countries tofollow. It is important, however, that this kind of strategyis supported by good science and that indicators formeasuring performance are included. There should alsobe a spirit of equal partners and equal accountability. The


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maintenance of mutual trust would be assisted by focusingnot just on farm practices but also on habitatmanagement issues.

Causes for Optimism

Other encouraging items included:

• Øystein Skaala reported on a study of genetic impactsin 7 rivers subject to long-term escapee pressure. His conclusion was that there were indications of genetic stability in the stocks of 4 of these.

• Harald Lura presented findings which indicated minimal genetic impact if escapees were maintained below 10% of river stocks. This suggests that we don’thave to achieve an escape level of absolute zero - which, in any case, is probably impossible.

• Fred Whoriskey studied the fate of escapees in New Brunswick and Maine through the fascinating use of electronic markers on live fish and found evidence of massive mortality during the first few days of freedom,particularly from seal predation.

• Peter Heuch compared two Norwegian fjords in terms of farm contributions to lice loads on wild salmon smolts. In one there was no perceptible impact and in the other there was a significant problem. He concluded that dissimilar hydrographies in the two fjords accounted for the difference. This supports the findings of other authors who have reported that the level of contribution by a farm to lice numbers on local wild salmonids is determined by both the size of the lice population on the farm and the hydrography of the area - thus, farms in more open locations or near the mouths of bays/fjords will be unlikely to have a significant impact.

• Using cautious language, Ron Stagg postulated that disease epidemics in farms will not necessarily result inepidemics in wild populations and that the risk can be reduced by good management.

Thus, for me there is more good news than bad but thereis no room for complacency and a lot of work remains tobe done. Arising from my participation in this symposiumI would like to suggest the basic elements of a wayforward.

The Way Forward - Escapes

• We need to get escapes down to as close to zero as possible. To do this we need to continue implementing the NASCO Liaison Group’s Guidelines

for Containment - improving the design of fish cages,matching appropriate technologies to site conditions,carrying out proper maintenance programmes and ensuring safe operational.procedures. We need to ensure all farming staff are trained in the essentials of escape prevention and they should all be educated in the potential impacts of escapes. I am sure that if the people on the ground were made aware of what we have heard here this week it would act as an incentive to greater effort in escape prevention.

• The Norwegian industry is promoting the idea of a national escapes commission to investigate and report on the causes of escapes as they occur. I would suggest that we should consider a similar strategy internationally, say within the Liaison Group.

• R&D has a role to play as well, such as developing lessvulnerable and more operator-friendly cage systems - Arne Fredheim’s novel net design is a good example of this kind of approach. A particular hobby horse of my own is that the marine cage farming industry reallyneeds the technologists to develop sonar-based methods of constantly monitoring the stock in a fish cage. As well as simplifying farm management this would alert the farmer to an escape event as soon as it begins.

• There has been a lot of debate here this week about the reduced fitness of farm stock and hybrids for survival in the wild. Perhaps we should encourage thebreeders to actually select for traits which would makethem totally unfit to survive or breed in the wild.

The Way Forward - Lice

In areas where there is a likelihood of impacts on wildsalmonids, farms must keep lice levels as close to zero asreasonably possible. Achieving this requires:

• An area management approach which results in synchronised treatments and regular fallowing.

• The availability of an adequate suite of anti-lice medications and hopefully, in the near future,vaccines. In this regard the procedures for the licensing of new products needs to be a lot more streamlined.

• The availability of spare farm sites so that fallowing canbe facilitated.

• Further work to be carried out on the use of wrasse in cages to remove lice from salmon. Ten years ago I was involved in trials with wrasse which were far from


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encouraging. But Per Gunnar Kvenseth is quite convincing and it would certainly be an ideal solution.

The Way Forward - General Principles

I think we’ve come a long way since Bath and both ourunderstanding of the interactions and our management ofthem have improved significantly. But we have a lot morework to do together and we need to further encouragecooperation between scientists, the farming industry,governments and the wild sector. We must regularlyremind ourselves that there is a lot more that joins usthan separates us - we are, in the end, all working withthe same species. Being aware of this will inspire us toconstantly seek win-win solutions.

6. Øyvind WalsøFirst of all I would like to support what has already beensaid during this symposium that in recent years we haveseen positive developments with regard to some of thefactors in aquaculture that cause negative impacts on wildsalmon stocks. We have also taken a huge step forwardin developing a common understanding of the implicationsof escapes of farmed fish for the wild salmon stocks andin recognising that it is necessary for the industry toincrease its efforts to prevent escapees. At the same timeit is clear that there is still some way to go before we cansay that all the issues we have been discussing for morethan 15 years now can be said to have been addressed.

The continuing escape of farmed salmon is regarded asthe most serious problem when we consider the negativeimpacts from aquaculture on the wild stocks of Atlanticsalmon. This has been a key topic at the previousmeetings, held in Loen, Norway in 1990, and in Bath,England in 1997. It has also been an important topic atthis symposium. It seems that both the fish farmingindustry and the wild salmon interests now sharecommon ground when it comes to the importance ofminimising escapees.

In spite of the effort that has been invested in improvingcontainment in net pens we see that the number of fishescaping has been fairly stable in recent years. While theproportion of farmed fish that escape may be declining,that improvement has until now been counteracted bythe increase in the scale of the production of farmedsalmon. As I said, the number of escapees remains toohigh and when it comes to their impact on wild salmonpopulations it is the number of escapees that is important.The numbers remain far too high.

Much has been said about physical containment measures- less about the possibilities of biological containment, forexample through the use of sterile salmon. The possibleuse of triploid fish was discussed at the previous meetingsas well as this week in Bergen. The issue was alsodiscussed at the NASCO/North Atlantic salmon farmingindustry Liaison Group Workshop held in Trondheim inAugust this year. I feel that the answers concerning howwell triploid salmon can perform in aquaculture aresomewhat confusing. The answer you get can vary fromtriploid salmon can perform as well as diploids to theirperformance is so poor that the industry will not acceptthem. There was also a suggestion that more effortshould be invested in research into alternative methodsfor sterilizing fish. To my mind this is a good idea thatdeserves further consideration in the future.

When it comes to sea-lice, it seems that the effort thathas been put into addressing this problem has paid off.We now know much more about how this problem canbe addressed and how it should be followed up bothregarding future research and the management of farms.Yesterday we heard a number of excellent presentationson this topic and from my point of view the results fromthis research were the most positive news from thissymposium.

And it also shows that if there is a challenge to beaddressed and if the wild fish interests and farminginterests really share common ground and work togetherthe probability for success is high and certainly muchhigher than if we were not working together.

So that, ladies and gentlemen, ends my personal summingup from this symposium. Presumably the next meeting, inseven years’ time, will be as interesting as this meeting hasbeen. Thank you very much!


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ANNEX 7List of Participants

Releasing smolts in the River Mandal, Norway as part of a stock rebuilding programme.


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Annex 7: List of Participants

Lord Alexander Antrim Worshipful Company of Fishmongers, England, UK Mr Vidar Baaroy Directorate of Fisheries, NorwayMr David Bean National Marine Fisheries Service, USADr Tillmann J. Benfey University of New Brunswick, CanadaDr Malcolm Beveridge Fisheries Research Services, Scotland, UKMr Raoul Bierach Directorate for Nature Management, NorwayMs Katherine Bostick WWF-US, USADr Karin Boxaspen Institute of Marine Research, NorwayMr Edward Branson Skretting,Wales, UKMr Paul Brooking Atlantic Salmon Federation, CanadaMr Sturla Brørs Office of the Finnmark County Governor, NorwayMr Alejandro Buschmann Universidad de Los Lagos, ChileMr Pablo Caballero Government of Galicia, SpainMs Fiona Cameron Sea Trout Group, Scotland, UKMr Jonathan Carr Atlantic Salmon Federation, CanadaMs Mary Colligan NOAA Fisheries, USAMs Helen Cooper Aquaculture Licence Appeals Board, Ireland Mr Richard Cowan DEFRA, England, UKProf Tom Cross Environmental Research Institute, IrelandDr Walter Crozier Department of Agriculture and Rural Development for Northern Ireland,

Northern Ireland, UKDr Graeme Dear Marine Harvest Scotland, Scotland, UK Mr David Dunkley Scottish Executive Environment and Rural Affairs Department, Scotland, UKMr Arne Eggereide Directorate for Nature Management, NorwayMr Lal Faherty The Western Regional Fisheries Board, IrelandMr Espen Farstad Norwegian Association of Hunters and Anglers, NorwayMs Merete Farstad Fylkesmannen I Sogn Og Fjordane, NorwayDr Bengt Finstad Norwegian Institute for Nature Research, NorwayDr Peder Fiske Norwegian Institute for Nature Research, NorwayMr Øyvind Fjeldseth Norwegian Association of Hunters and Anglers, NorwayMs Jennifer Ford Dalhousie University, CanadaDr Gregory Forde Western Regional Fisheries Board, IrelandDr Torbjørn Forseth Norwegian Institute for Nature Research, NorwayDr Arne Fredheim Sintef Fisheries and Aquaculture, NorwayDr Patricia Gallaugher Simon Fraser University, Canada Dr Paddy Gargan Central Fisheries Board, IrelandMr Dagfinn Gausen Directorate for Nature Management, NorwayMr Phil Gilmour Scottish Executive Environment and Rural Affairs Department, Scotland, UKDr Kevin Glover Institute of Marine Research, NorwayDr Kari Grave Norwegian School of Veterinary Science, NorwayMr Douglas E Grout New Hampshire Fish and Game Department, USA


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Dr Sigurdur Gudjonsson Institute of Freshwater Fisheries, IcelandDr Lars Petter Hansen Norwegian Institute for Nature Research, NorwayDr Neil Hazon University of St Andrews, Scotland, UKMs Gunn Helen Henne County Governor of Sogn og Fjordane, NorwayDr Peter Andreas Heuch National Veterinary Institute, NorwayDr Kjetil Hindar Norwegian Institute for Nature Research, NorwayMr Ross Hinks Council of the Conne River Micmacs, CanadaMr Knut Hjelt FHL Aquaculture, NorwayDr Jens Christian Holm Directorate of Fisheries, NorwayMs Marianne Holm Institute of Marine Research, NorwayDr Peter Hutchinson Assistant Secretary, NASCOMr Arni Isaksson Directorate of Freshwater Fisheries, IcelandMr Tore Jakobsen European Commission, BelgiumMr Stig Johansson Directorate for Nature Management, NorwayDr Bror Jonsson Norwegian Institute for Nature Research, NorwayMr Knut Jørstad Institute of Marine Research, NorwayMr Atle Kambestad Fylkesmannen Hordaland, NorwayDr Lars Karlsson Swedish Board of Fisheries, SwedenDr Marja-Liisa Koljonen Finnish Game and Fisheries Research Institute, FinlandMr Knut Kristoffersen Fylkesmannen I Tromso, NorwayMr Frode Kroglund NIVA, NorwayMr Håkon Kryvi Fylkesmannen Hordaland, NorwayMr Per Gunnar Kvenseth Norsk Sjømatsenter, NorwayDr Oleg Lapshin Federal Research Institute of Fisheries and Oceanography (VNIRO), RussiaDr Harald Lura Ambio AS, NorwayMr Patrick Martin Fondation Saumon, FranceDr Philip McGinnity Marine Institute, IrelandMr Joseph McGonigle Aqua Bounty Farms, USAMr Helge Midttun Fjord Seafood ASA, Norway Dr Paloma Morán Universidade de Vigo, SpainDr Kentaro Morita Hokkaido National Fisheries Research Institute, Japan Mr Harald Muladal Fylkesmannen I Finnmark, NorwayMs Chrys-Ellen Neville Fisheries and Oceans, CanadaMiss Margaret Nicolson PA to the Secretary, NASCODr Niall Ó Maoiléidigh Marine Institute, IrelandMr Pat O’Reilly Dreamstreams,Wales, UKMr Sumarlidi Oskarsson Directorate of Freshwater Fisheries, IcelandDr Sylvain Paradis Department of Fisheries and Oceans, CanadaMs Susan Parker Dreamstreams,Wales, UKMr Daniel Pendrey Fisheries Research Services, Scotland, UKMr Michael Penston Fisheries Research Services, Scotland, UKMr Geoffrey Perry Department of Fisheries and Oceans, CanadaMr Chris Poupard European Anglers Alliance, England, UK


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Dr Sergei Prusov PINRO, RussiaMr Gorm Rasmussen Danish Fisheries Research Institute, DenmarkMr James Ryan International Salmon Farmers’ Association, IrelandDr Odd Terje Sandlund Norwegian Institute for Nature Research (NINA), NorwayMs Maria Saura Universidade de Vigo, SpainMr David Scruton Department of Fisheries and Oceans, CanadaDr Øystein Skaala Institute of Marine Research, NorwayDr Ove Skilbrei Institute of Marine Research, NorwayMr Berkley Slade Department of Fisheries and Oceans, CanadaDr Ron M Stagg Fisheries Research Services, Scotland, UKMr Jarle Steinkjer Directorate for Nature Management, NorwayMr Arne Storset Aqua Gen AS, NorwayDr Igor Studenov SevPINRO, RussiaDr Terje Svåsand Institute of Marine Research, NorwayDr Martin A Svenning Norwegian Institute for Nature Research (NINA), NorwayDr John Thorpe University of Glasgow, Scotland, UK Prof Christopher Todd University of St Andrews, Scotland, UKMs Wendy Tymchuk University of British Columbia, CanadaMs Aina Valland FHL Aquaculture, NorwayDr Alan Walker CEFAS, Fisheries and Aquaculture Science, England, UKMr Øyvind Walsø Directorate for Nature Management, NorwayMr John Webb Atlantic Salmon Trust, Scotland, UKMr Vidar Wennevik Institute of Marine Research, NorwayDr Ken Whelan President of NASCO, Marine Institute, IrelandDr Fred Whoriskey Atlantic Salmon Federation, CanadaDr Malcolm Windsor Secretary, NASCOMr Ulf Winther Sintef Fisheries and Aquaculture, NorwayMr Aage Wold Norske Lakseelver, (Norwegian Salmon Rivers), Norway

NINA SPECIAL REPORT 34ISSN: 0804-412X ISBN 10: 82-426-1736-8 ISBN 13: 978-82-426-1736-1

Norwegian Institute for Nature ResearchNINA Head OfficePostal address: NO-7485 Trondheim, NORWAYVisiting address:Tungasletta 2, NO-7047 Trondheim, NORWAYPhone: +47 7380 1400Fax: +47 7380 1401Organisation number 9500 37 687http//www.nina.no

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Bergen Covers/inside pages - NASCO · NINA SPECIAL REPORT 34 Norwegian Institute for Nature Research (NINA) Conveners’ Report Lars Petter Hansen Malcolm Windsor Hansen, L.P. & Windsor,

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