Sea lice infestation on wild salmonids in the southern ... · Abstract The sea lice species, Lepeophtheirus salmonis and Caligus elongatus are natural parasites on salmonid fishes.

Sea lice infestation on wild salmonids

in the southern part of the Icelandic Westfjords

Eva Dögg Jóhannesdóttir

Department of Aquaculture and Fish Biology Hólaskóli – Háskólinn á Hólum

(Hólar University College)

2019

Sea lice infestation on wild salmonids in the southern part of the Icelandic Westfjords

Eva Dögg Jóhannesdóttir

90 eininga ritgerð til Magister Scientarium prófs í sjávar- og vatnalíffræði (90 ECTS thesis submitted in partial fulfillment of a

Magister Scientiarum degree in Aquatic Biology)

Leiðbeinandi

(Advisor) Skúli Skúlason

Fiskeldis- og fiskalíffræðideild (Department of Aquaculture and Fish Biology)

Hólaskóli – Háskólinn á Hólum (Hólar University College)

Hólar, maí (May) 2019

Sea lice infestation on wild salmonids in the southern part of the Icelandic Westfjords

Sea lice infestation in South Westfjords

90 ECTS ritgerð til Magister Scientarium til prófs í sjávar- og vatnalíffræði

90 ECTS thesis submitted in partial fulfillment of a Magister Scientarium degree in Aquatic

Biology

Copyright © 2019 Eva Dögg Jóhannesdóttir

Öll réttindi áskilin / (All rights reserved)

Fiskeldis- og fiskalíffræðideild (Department of Aquaculture and Fish Biology)

Hólaskóli – Háskólinn á Hólum (Hólar University College)

Hólar í Hjaltadal

551 Sauðárkrókur

Iceland

Sími (Telephone): 455 6300

Bibliographic information:

Eva Dögg Jóhannesdóttir, 2019, Sea lice infestation on wild salmonids in southern part of the

Icelandic Westfjords, Fiskeldis- og fiskalíffræðideild (Department of Aquaculture and Fish

Biology), Háskólinn á Hólum (Hólar University College), 58 bls. (pp 58)

Printing: Hólar í Hjaltadal, Iceland, May 2019

Abstract

The sea lice species, Lepeophtheirus salmonis and Caligus elongatus are natural parasites on

salmonid fishes. They feed on their mucus, skin and blood and by that induce stress responses

in their hosts and sometimes carry pathogens that infect the host. If they infest in great numbers,

they can kill the host. In areas with salmonid aquaculture in sea cages, wild salmonids tend to

have more infestation of sea lice (mainly L. salmonis) than in areas without aquaculture.

Farming of salmonids in sea cages is relatively new in Iceland. Thus, it is important to gather

information on the infestation situation on wild salmonids, especially in the Westfjords where

culture of salmon has been growing. Infestation on wild salmonids was examined in 2014 in

Arnarfjörður and in Tálknafjörður and Patreksfjörður the following year. Atlantic salmon

(Salmo salar) farming in sea cages was practiced in all fjords of the southern Westfjords in

2017. In the current study infestation of sea lice on wild salmonids, i.e. sea trout (Salmo trutta)

and Arctic charr (Salvelinus alpinus), was examined in this area in 2017. Samples were taken

of wild fish in three sampling from June to September and results compared to earlier findings,

as well as with infestation of sea lice on salmon in sea cages in 2017. Results show an increase

in infestation and indicate negative effects on wild populations. Comparing sea lice infestation

on farmed salmon and wild sea trout, it is evident that the two species of sea lice infest the two

species differently.

Útdráttur

Laxalús, Lepeophtheirus salmonis og grálús Caligus elongatus, eru náttúruleg sníkjudýr á

laxfiskum í sjó. Lýsnar nærast á slímhúð, roði og blóði fiskanna og valda þannig streitu hjá

þeim. Þær geta einar og sér valdið dauða fiska séu þær í miklum mæli en geta auk þess borið

með sér aðra sýkla. Rannsóknir sýna að á svæðum þar sem eldi laxfiska í sjókvíum er stundað

eru villtir laxfiskar meira smitaðir af sjávarlús, einna helst laxalús, heldur en svæðum án eldis.

Eldi á laxi (Salmo salar) í sjó er nýleg atvinnugrein á Íslandi og því mikilvægt að afla þekkingar

um sjávarlýs á villtum laxfiskum. Lúsasmit var kannað á villtum laxfiskum í Arnarfirði árið

2014 og í Tálknfirði og Patreksfirði árið 2015. Laxeldi var stundað í öllum fjörðum

sunnanverðra Vestfjarða árið 2017. Í þessu verkefni var lúsasmit villtra laxfiska, sjóbirtings

(Salmo trutta) og sjóbleikju (Salvelinus alpinus), kannað í öllum fjörðum sunnanverðra

Vestfjarða frá júní til september 2017 og niðurstöður bornar saman við lúsatalningar í kvíum á

svæðinu, sem og fyrri athuganir á villtum laxfiskum. Niðurstöður sýna aukið smit villtra

laxfiska á svæðinu og gefa vísbendingu um neikvæð áhrif á þessa stofna. Einnig kom í ljós að

lúsategundirnar tvær virðast smita eldislaxa og villta sjóbirtinga á ólíkan hátt.

Elsku dóttir mín

Við lærðum á þolinmæðina saman

i

1. Table of Contents

1. Table of Contents ............................................................................................................... i

Myndaskrá ................................................................................................................................ ii

List of Figures ........................................................................................................................... 2

List of Tables ........................................................................................................................... iii

Acknowledgements ................................................................................................................... iv

2. Sjávarlýs á laxfiskum ............................................................................................................ 1

2.1 Inngangur .....................................................................................................................................1

2.2 Lífsferill og atferli laxalúsar .......................................................................................................2

2.3 Útlit og greining laxa- og grálúsar .............................................................................................6

2.4 Áhrif á laxfiska ............................................................................................................................8

2.5 Sjávarlýs við strendur Íslands ....................................................................................................9

Heimildir.................................................................................................................................. 11

3. Sea lice infestation on wild salmonids in southern part of the Icelandic Westfjords ...... 18

3.1. Introduction ..............................................................................................................................18

3.2 Materials and methods ..............................................................................................................23

3.3 Results.........................................................................................................................................28

3.3.1 Sea lice parameters ..............................................................................................................................29

3.3.2 Different lice stages .............................................................................................................................31

3.3.3 Lice counts from Arnarlax ...................................................................................................................33

3.4 Discussion ...................................................................................................................................35

3.5 Conclusions ................................................................................................................................37

References ............................................................................................................................... 38

Appedixes .........................................................................................................................................44

ii

Myndaskrá

Mynd 1. Lífsferill laxalúsar, mynd aðlöguð úr Igboeli o.fl. 2014. .................... 4

Mynd 2. Þroskun æxlunarfæra kvenlúsar. Höfuðbolur (e. cephalothorax CT) nær að æxlunarfærum (e. genitalsegment GS) sem eru utan um afturenda

(e. abdomen), úr æxlunarfærum hanga tveir eggjastrengir (sjá T5 og T6).

Mynd frá Eichner o.fl. (2008). ........................................................................................ 5

Mynd 3. Copepodid lirfur laxalúsar (til vinstri) og grálúsar (til hægri).

Mælistikur eru 0,1 mm. Samsett mynd frá Scram (2004). ................................ 6

Mynd 4. Þroskun laxalúsar frá copepodid að fyrsta forstigi fullorðins stigs

(e. pre-adult I). Kyngreining chalimus stiga var gerð eftir myndum eftir hamskipti lúsa í forstig fullorðins stigs, slík kyngreining er annars ekki

möguleg. Mynd frá Eichner o.fl. (2015). ................................................................... 7

Mynd 5. Grálús, chalimus og fullorðnar kvenlýs ásamt kvenlús með

eggjastrengi. Hálfmánar á höfði sýnilegir © EDJ ................................................... 8

List of Figures

Figure 1. Westfjords; South region marked in a black box © EDJ. .............. 18

Figure 2. Salmon farming in south region of the Westfjords in 2017. Hlaðseyri in Patreksfjörður, Laugardalur in Tálknafjörður and Haganes,

Steinanes, Hringsdalur and Tjaldanes in Arnarjförður marked with a black

triangle © EDJ.................................................................................................................... 20

Figure 3. Research area in two sites in Patreksfjörður (Blue), Tálknafjörður

(Green) and Arnarfjörður (Blue and red). ............................................................... 24

Figure 4. Net deployment in sea, dimensions are not to scale. Figure © EDJ................................................................................................................................................... 25

Figure 5. Prevalence of L. salmonis in all areas over the research period.

Blue is Tálknafjörður, orange is Arnarfjörður and gray Patreksfjörður. ...... 29

Figure 6. L. salmonis abundance in Patreksfjörður, Tálknafjörður and Arnarfjörður for samplings 1 (blue), 2 (red) and 3 (green). Boxes show the

interquartile range, horizontal line the median, x marks the mean abundance, whiskers maximum and minimum values and points outliers.

Note different values in y-axis for Patreksfjörður (pink box). ........................ 30

Figure 7. L. salmonis intensity in Patreksfjörður, Tálknafjörður and Arnarfjörður for samplings 1 (blue), 2 (red) and 3 (green). Boxes show the

interquartile range, horizontal line the median, x marks the mean

iii

abundance, whiskers maximum and minimum values and points outliers.

Note different values in y-axis for Patreksfjörður (pink box). ........................ 30

Figure 8. Different life stages of L. salmonis and C. elongatus in all locations and samplings. Each graph is marked with location, Tálknafjörður (Tálkn),

Arnarfjörður (Arn) and Patreksfjörður (Patr) and number for period. Graphs start out with L. salmonis copepodid (Cop), Chalimus I and II (Chal), Preadult F I and II (PreF), Preadult M (PreM), adult females (F), adult males

(M), gravid females are represented as orange in the pillar for females. Last three pillars to right are for C. elongatus: Chalimus I, II, III and IV (Chal), adult female (F) and adult male (M), gravids as L. salmonis. Note the

different scale on the y-axis between samples 1, 2 and 3 and for

Patreksfjörður..................................................................................................................... 32

Figure 9. Distribution of life stages depicted as frequency of whole sample

from sampling 1-3 in all locations. ............................................................................. 33

Figure 10. Sea lice abundance in Arnarlax’s farming areas in Arnarfjörður: Hringsdalur, Haganes, Steinanes, in Patreksfjörður: Hlaðseyri and in

Tálknfjörður: Laugardalur. Note the different scale on the y-axis. ............... 34

List of Tables

Table 1. Dates of samplings in the three fjords. .................................................. 25

Table 2. A schema for estimating population effect made for Arctic charr

and sea trout first time migrant to sea <150 g.................................................... 27

Table 3. A schema for estimating population effect made for mature Arctic

charr and sea trout >150 g. ......................................................................................... 27

Table 4. Mean weight (g) and length (mm) of salmonids (Arctic charr and sea trout) from all samplings and locations with standard deviation (SD)

and range from smallest to largest. .......................................................................... 28

Table 5. Assessment of population effect in all locations over all samplings.

Calculations are based on recommendations from Taranger et al. (2012) for both fish under 150 g and over 150 g. Green = small effect (<10%),

yellow = moderate effect (10-30%), red = great effect (>30%). ................ 31

iv

Acknowledgements

I must first sincerely thank my advisor Skúli Skúlason for his patience and guidance, you have

helped me grow as a scientist and with your beautiful philosophy on both life and life science

you have sharpened my skills and beliefs. Kári Heiðar Árnason for checking up on me as I

didn’t get the opportunity to do my studies at Hólar and was for the most part far away and

alone in my studies. Thank you for never forgetting me, pushing me and believing in me.

Thanks to Guðni Guðbergsson for serving on my committee and providing swift and good

feedback on my project. Also, thanks to Árni Kristmundsson for agreeing to serving as my

external examiner.

I am very grateful for the financial support from RORUM ehf. as well as Þorleifur Eiríksson

and Guðmundur Víðir Helgason for professional advice on species identification as well as

proofreading and talking me through tough times. Sussie Dalvin at the Norwegian Institute for

Marine Research for helping a complete stranger with species identification. The farming

companies Arnarlax and Arctic Fish for providing funds for boat rides to sample salmonids for

the project as well as Háafell for providing gill-nets. The rescue companies Tálkni and Blakkur

for agreeing to use their equipment for these trips as well as assisting with fishing and carrying

fishing equipment, especially Guðmundur Björn Þórsson (Bjössi) and Jón Ólafur Ásgeirsson

with Tálkni and Guðmundur Pétur Halldórsson at Blakkur for safe sampling trips as well as

good company. Thank you to Margrét Thorsteinsson at Westfjords Nature Center for assisting

with sampling as well as the use of the center’s laboratory.

At the farming companies I especially want to thank Þóra Jörundsdóttir at Arnarlax for

assistance in planning, Johan Hansen (my boss) at Arctic Fish for flexible hours on the job,

endless patience and understanding.

My friends and family for moral support; Jóhanna, Inga Jóna, Sigge, Solla, Siggi P, mom and

dad thank you for countless hours of phonecalls, coffee cups and walks letting me talk your

ears off. Lilja Magnúsdóttir and Nancy Rut Helgadóttir for also doing useful and swift

proofreadings. Ann Cochu, thank you for priceless help, support and the best company with

sampling and dissecting. I will never forget you Galway girl. Thank you all, for always

believing in me.

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2. Sjávarlýs á laxfiskum

2.1 Inngangur

Í þessum kafla verður gerð grein fyrir líffræði sjávarlúsa og þá einkum laxalúsar

(Lepeophtheirus salmonis), þar sem heimildir eru hvað flestar um þá tegund. Einnig verður

tíundað hvað er vitað um laxa- og fiskilús (Caligus elongatus) við Íslandsstrendur og hvað

vantar upp á þá þekkingu.

Þegar talað er um sjávarlýs (e. sea lice) á laxfiskum er að jafnaði átt við laxalús og fiskilús

sem í þessari grein verður nefnd grálús eftir grásleppunni sem hún virðist sækja mikið í

(Nordland 2017). Þessi dýr eru ekki eiginlegar lýs heldur krabbadýr sem finnast í öllum

hafsvæðum norðurhvelsins (Costello 2006). Þessi krabbadýr eru þekkt sníkjudýr á fiskum

og þar sem þær nærast að mestu leyti á blóði þeirra (Pike og Wadsworth 2000, Whelan

2010) er lúsa samlíkingin líklega dregin þaðan. Laxalúsin er mjög sérhæfð á laxfiskum eins

og nafnið gefur til kynna. Heimildir um laxalús eru til frá 17. öld en henni var fyrst lýst og

gefið nafnið Lepeophtheirus salmonis af dýrafræðingnum Henrik Nikolai Krøyer árið 1837.

Dýrafræðingurinn Alexander von Nordmann lýsti grálúsinni og gaf henni nafnið Caligus

elongatus árið 1832.

Þessi sníkjukrabbadýr hafa þróast með fiskunum og hefur laxalúsin aðlagað lífsferil sinn að

laxfiskum og þá helst sjóbirting (Salmo trutta) og Atlantshafslaxi (Salmo salar) (Boxaspen

2006, Yazawa o.fl. 2008). Grálúsin er hins vegar ekki hýsilsérhæfð og hefur fundist á yfir

80 tegundum fiska (Landsberg o.fl. 2011). Áhugi á þessum sníkjudýrum hefur hvað helst

snúið að laxeldi í sjó en í sjókvíum hafa lýsnar aðgang að hýslum í miklum þéttleika. Þær

hafa valdið miklum skaða í sjókvíaeldi á löxum en þær valda streitu hjá fiskunum og opna

sár sem opna leiðir fyrir sýkingar af öðru tagi. Í miklum mæli geta þær einar og sér leitt til

dauða fiskanna (Costello 2006). Laxalúsin hefur óneitanlega fengið meiri athygli en

grálúsin, vegna skaðans sem hún veldur í sjóeldi á löxum (Costello 2006). Hún er stærri en

grálúsin og greinilegri á fiskum þar sem hún er oftast dekkri að lit. Fjölgun laxalúsa í

umhverfinu vegna fiskeldis er talin ein mesta ógn við villta stofna laxfiska í Noregi (Anon

2018). Heimildir eru þó til frá síðustu öld þar sem lax var svo sýktur af laxalús af náttúrunnar

hendi, þ.e. án laxeldis í sjó, að dauði hlaust af (Torrissen o.fl. 2013). Grálúsin og laxalúsin

hafa þó nú þegar gert vel vart við sig í íslensku laxeldi og valdið töluverðu tjóni á

Vestfjörðum. Brugðist hefur verið við þessu á síðustu árum með lyfjameðferð á löxum í

sjókvíum í Dýrafirði, Arnarfirði og Tálknafirði (óbirt gögn Arnarlax og Arctic Sea Farm,

Fisksjúkdómanefnd 2017, Matvælastofnun 2018). Í öllum þessum tilvikum var það mikið

magn lúsa á fiskum að meðhöndlun þótti nauðsynleg vegna dýravelferðar. Eldisfyrirtækin

leita nú mikið að fyrirbyggjandi og umhverfisvænum aðferðum til að stemma stigu við

lúsunum. Til eru fiskar sem éta lýs af öðrum fiskum sem kallaðir eru hreinsifiskar og hafa

verið notaðir annars staðar í heiminum (Boxaspen 2006). Sem dæmi hafa hrognkelsi

(Cyclopterus lumpus) verið notuð sem hreinsifiskar bæði í Færeyjum og Noregi til að

stemma stigu við laxalúsinni í eldiskvíum en tegundin hentar vel í köldum sjó (Imsland o.fl.

2014). Nú eru hrognkelsi því notuð í Dýrafirði og Arnarfirði til að éta lýs af löxum sem

hefur gefist ágætlega. Grálúsin virðist þó sækja mikið í hrognkelsin og finnst á þeim í

miklum þéttleika (athuganir höfundar, Nordland 2017).

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Heimkynni laxalúsar eru á öllu norðurhveli jarðar og hún sækir í Kyrrahafslaxa

(Oncorhynchus spp.), Atlatnshafslax, bleikju (Salvelinus alpinus) og sjóbirting (Salmo

trutta). Grálúsin finnst eingöngu í Norður-Atlantshafshafi (Boxaspen 2006). Hvorki laxalús

né grálús finnast í Síle, þar sem er mikið eldi á Atlantshafslaxi, en þar veldur Caligus

rogercresseyi eða Sílelúsin vandræðum í eldinu. Lúsin fannst fyrst í sjókvíunum árið 1997

(Bravo 2003, Johnson o.fl. 2004) og hefur síðan verið rannsökuð þó nokkuð (Johnson o.fl.

2004). Sílelúsin og grálúsin eru líkar enda skyldar tegundir (Treasurer og Bravo 2011) en

rannsóknir á Sílelúsinni gætu nýst til að skilja líffræði grálúsarinnar betur.

2.2 Lífsferill og atferli laxalúsar

Lífsferill fyrrnefndra lúsategunda er áþekkur, en laxalúsin hefur verið mest rannsökuð.

Lýsnar hafa átta þroskastig en á meðan laxalúsin hefur tvö stig sem eru eins konar forstig

fullorðins stigs (e. Pre-adult I og II), eru þau stig ekki til staðar hjá grá- og Sílelúsinni

(Gonzáles og Carvajal 2003). Laxalúsin hefur einnig tvö lirfustig þar sem hún situr föst á

fiskinum og kallast þau chalimus I og II (Hamre o.fl. 2013) meðan grá- og Sílelúsin hafa

fjögur slík stig eða chalimus I, II, III og IV (Gonzáles og Carvajal 2003).

Laxalúsin, hefur aðskilin kyn og átta þroska stig (Mynd 1). Sviflægar lirfur klekjast úr

eggjum sem liggja í strengjum utan á kvendýrinu. Rannsóknir á laxlús úr sjókvíaeldi í

Noregi hafa sýnt að egg hennar klekjast eftir 8,7 daga við 10°C meðan klak getur tekið allt

að 45 daga við 2°C (Boxaspen og Næss 2000). Fyrsta lirfustigið kallast nauplius I sem hefur

hamskipti í annað lirfustig, nauplius II eftir 9 klst ef sjórinn er 15°C en getur tekið 52 klst

við 5°C. Þroskun nauplius II tekur mun lengri tíma en hamskipti verða eftir 36 klst við 15°C

sjávarhita en 170 klst. við 5°C. Þriðja og síðasta lirfustigið kallast copepodid en á því stigi

þarf dýrið að finna sér hýsil. Lirfan getur verið án hýsils í allt að tvær vikur en það fer eftir

sjávarhita. Því hærri hiti því styttri tíma hefur hún, en hún lifir á forða á þessu stigi. Eftir 10

daga reynist lirfunni erfitt að festa sig á hýsil ef sjávarhiti er undir 12°C (Boxapen og Næss

2000). Þroskunartími lengist því með lækkandi sjávarhita en þegar hann fer niður í 2°C tekur

ferlið frá klaki að copepodid stigi allt að tvo mánuði. Sýnt hefur verið fram á að við svo

lágan sjávarhita lifa aðeins 25% lirfa fram að copepodid stiginu (Boxapen og Næss 2000).

Samsing o.fl. (2016) sáu að sjávarhiti hefur áhrif á klak og þroska laxalúsar. Í rannsókn

þeirra, sem var framkvæmd á lúsum úr sjókvíum í Noregi, kom fram að við 3°C klekst

aðeins um 30% eggja út og náðu engar lirfur að þroskast meira en í nauplius II. Enn fremur

sýndu þau fram á að við 5°C hita klekjast um 85-90% eggja út og lirfur ná fullum þroska.

Hiti hefur einnig áhrif á stærð fullvaxinna lúsa sem verða stærri með minnkandi hita allt

niður í 3°C, þar sem dregur úr vexti á meðan stærð eggja eykst mikið. Þó kom einnig í ljós

að við 20°C dregur aftur úr vexti (Samsing o. fl. 2016). Sýnataka í rannsókn Samsing o. fl.

(2016) fór fram við strendur Suðvestur Noregs en mun norðar hjá Boxaspen og Næss (2000),

og þar af leiðandi í kaldari sjó að meðaltali. Mismunandi sjávarhiti milli svæða getur leitt til

mismunandi aðlögunar lúsa (Costello 2006). Þess ber þó að geta að Samsing o. fl. (2016)

höfðu stöðugt ljós hjá lúsunum allan rannsóknartímann en Boxapen og Næss (2000) notuðu

12/12 ljósastýringu. Þetta bendir til að birta hafi einhver áhrif á þroska og lífslíkur lúsanna.

Copepodid lirfan hefur það hlutverk að finna réttan hýsil, þ.e. laxfisk til að lifa af og þroskast

(Losos 2008, Pert o.fl. 2009). Hún getur fært sig upp og niður í vatnssúlunni og eru

hreyfingarnar háðar birtu. Þær er helst að finna nálægt yfirborði sjávar yfir daginn en fara

dýpra að nóttu til (Heuch o.fl. 1995). Þetta getur haft áhrif á leit lirfunnar að hýsli þar sem

3

laxfiskar halda sig dýpra á daginn en í yfirborðið á næturnar. Þannig eru meiri líkur á að

lirfur og fiskar hittast á þessari leið (Samsing o.fl. 2016).

Selta hefur einnig áhrif á copepodid lirfuna, sem forðast seltu undir 27 ppt. Þegar selta fer

undir 29 ppt minnkar lifun lirfa sem og geta þeirra til að festast á hýsli (Bricknell o.fl. 2006).

Lirfurnar skynja einnig hreyfingu fisks í vatninu og nota þá skynjun til að ráðast á hann

þegar hann syndir að þeim (Heuch o.fl. 2007). Allt þetta hjálpar lirfunni að finna hýsil, en

ekki endilega réttan hýsil. Þar kemur til lyktarskyn, en lúsin (einnig seinni þroskastig en

copepodid lirfan) nýtir lyktarefni laxfiska í vatninu til að þekkja þá í sundur frá öðrum

fisktegundum (Mordue og Birkett 2009). Lyktarskyn lirfa og fullorðinna lúsa er að finna í

skyn-fálmurum (e. antennae) framan á þeim sem hafa fjaðurlík hár (e. setae) sem geta bæði

virkað sem hreyfiskynjarar og lyktarskynjarar (Bron o.fl. 1991, Hull o.fl. 1998, Mordue og

Brikett 2009).

Copepodid lirfan festir sig fyrst á hýsilinn með grip-fálmurum sem eru staðsettir framarlega

á dýrinu, fyrir aftan fyrstu hærðu skyn-fálmarana. Lirfan getur enn losað sig af hýslinum á

þessum tímapunkti og notar fæturna (e. maxillipeds) til að skoða hýsilinn nánar. Hún þrýstir

framendanum að hýslinum meðan hún skríður um hann og setur þannig skyn-fálmarana í

snertingu við hann. Lirfan getur því hætt við að festa sig komist hún að því að hýsillin henti

ekki (Bron o.fl. 1991). Ef lirfan telur sig hafa fundið réttan hýsil og góðan stað á honum

grípur hún fast í roð hans og stingur grip-fálmurunum á kaf þannig að roðið lyftist upp, en

þetta getur tekið nokkrar tilraunir. Þegar lúsin hefur fest sig getur hún byrjað að nærast á

slími, húðfrumum og blóði hýsilsins (Costello 2006, Pike og Wadsworth 2000, Whelan

2010). Næst myndar hún stilk undir húðinni sem festir hana betur. Stuttu seinna hefur lirfan

hamskipti í næsta lirfustig, chalimus I, og festir sig betur með vökva sem virkar eins og lím

(Bron o.fl. 1991). Chalimus I hefur síðan hamskipti yfir í chalimus II sem svo hefur

hamskipti yfir í einskonar forstig fullorðins stigs (e. pre-adult). Þessi síðustu hamskipti frá

lirfustigi verða um 12 dögum eftir að copepodid lirfan festir sig fyrst á hýsilinn hjá

karlkynslúsum en eftir um 14 daga hjá kvenkynslúsum (Hamre o.fl. 2013).

Við hamskipti í fyrsta forstig fullorðinsstigs (pre-adult I) losnar lúsin og getur aftur skriðið

um hýsilinn. Til að halda sér á hýslinum notar hún höfuðbolinn (cephalothorax) eins og

sogskál (Wagner o.fl. 2008). Hún getur einnig farið af hýslinum og synt á nýjan hýsil. Á

þessu stigi er fyrst hægt að kyngreina dýrin (Eichner o.fl. 2015).

4

Mynd 1. Lífsferill laxalúsar, mynd aðlöguð úr Igboeli o.fl. 2014.

Hamskipti eiga sér aftur stað og þroskast lúsin þá yfir í annað forstig fullorðinsstigs (pre-

adult II). Hamskipti frá öðru forstigi fullorðinsstigs yfir í fullvaxta lús eiga sér næst stað og

þá verður lúsin loks kynþroska (Mynd 1). Kvenlúsin er tvöfalt stærri en karllúsin en

fullvaxin kvenlús er um 12 mm og getur náð 29 mm með eggjastrengjum, meðan karllúsin

er um 6 mm (Igboeli o.fl. 2014).

Fullorðnar lýs þrífast illa eftir því sem selta minnkar og losna af laxfiskum þegar þeir ganga

í ferskvatn (Bricknell o.fl. 2006). Finstad o.fl. (1995) sáu að laxalýs geta lifað á bleikju í allt

að þrjár vikur í ferskvatni á meðan t.d. Connors o.fl. (2008) sýndu að lýs drepast og detta af

Kyrrahafslöxum fljótlega eftir að þær koma í ferskvatn. Þetta bendir til að aðrar aðstæður

spili hér inní. Vatnshiti var svipaður í báðum rannsóknum en munurinn getur legið í þeim

fiskitegundum sem nýttar voru en komið hefur í ljós að regnbogasilungur (Oncorhynchus

mykiss) og coho lax (Oncorhynchus kisutch) sýna meira ónæmisviðbrögð við sýkingu

laxalúsar en Atlantshafslax (Fast o.fl. 2002, Vargas-Chacoff o.fl. 2016). Það er kannski

skýringin milli rannsóknar á bleikju og Kyrrahafslöxum. Einnig voru mun minni fiskar

notaðir hjá Connors o.fl. (2008) eða aðeins um 3 gr á móti rúmlega 300 gr hjá Finstad o.fl.

(1995) en stærri fiskur gefur mögulega lúsunum fleiri tækifæri til að færa sig um á honum

og grafa sig inn milli hreisturs og ofan í slími til að verjast ferskvatninu.

Æxlunaratferli hefst oftast með fullvaxta kynþroska karllús og ókynþroska kvenlús á pre-

adult II stigi. Karllúsin heldur kvenlúsinni með gripfálmurum en á meðan framleiðir

kvenlúsin tímabundinn anga að framan og festir sig við hýsilinn áður en hún hefur

hamskipti. Kvenlúsin hefur síðan hamskipti á meðan karlinn heldur sér föstum við hana.

5

Eftir hamskiptin færir hann sig og festir sig á æxlunarfæri kvenlúsin sem þá er orðin

kynþroska. Þegar hér er komið losar kvenlúsin sig af hýslinum og æxlun á sér stað með því

að karllúsin lyftir upp æxlunarfærum kvenlúsarinnar með fótum sínum (maxillipeds).

Karllúsin notar síðan sundfæturna til að flytja tvö sæðishylki (e. spermatophores) að

kvenlúsinni og festa þau á æxlunarfæri hennar. Hann heldur þeim þar í nokkurn tíma til að

tryggja að þau sitji föst áður en hann fer aftur frá kvenlúsinni. Þetta ferli getur tekið hátt í 6

daga frá því að karllúsin festir sig fyrst á kvenlúsina. Karllúsin byrjar að leita að nýjum maka

um leið og hann yfirgefur kvenlúsina, en þá lokast æxlunarfæri hennar og hún æxlast ekki

aftur (Ritchie o.fl. 1996). Sæðishylkin fara inn í sæðisgeymslu (e. recepriculum seminis)

kvenlúsarinnar en æxlunarfæri hennar ná fyrst fullri stærð eftir um tvær vikur og

eggjastrengir verða sýnilegir eftir um 10 daga (Eichner o.fl. 2015, Mynd 2). Eggin fara í

gegnum rás þar sem þau eru þakin vökva eða lími (e. cement) áður en þau ýtast í einfaldri

röð út um þar til gerð op (e. gonopore) á æxlunarfærum kvenlúsarinnar sitt hvoru megin við

afturendann. Límið myndar himnu utan um eggin sem heldur þeim í svokölluðum

eggjastrengjum (Ritchie o.fl.1996). Kvenlúsin virðist því vera með tvö skott þegar eggin eru

komin út. Í himnunni eru eggin varin og þroskast þar til þau klekjast í nauplius I.

Mynd 2. Þroskun æxlunarfæra kvenlúsar. Höfuðbolur (e. cephalothorax CT) nær að æxlunarfærum (e. genitalsegment GS) sem eru utan um afturenda (e. abdomen), úr

æxlunarfærum hanga tveir eggjastrengir (sjá T5 og T6). Mynd frá Eichner o.fl. (2008).

Kvenlús laxalúsarinnar lifir í 190-210 daga frá því að hún verður fullvaxta. Hún framleiðir

eggjastrengi um leið og æxlunarfæri hennar hafa náð fullum vexti sem gerist ekki fyrr en

eftir fyrstu æxlun. Hún geymir sæði karllúsarinnar og framleiðir eggjastrengi alla sína

lífdaga sem fullvaxin kvenlús (Heuch et al. 2000, Mustafa et al. 2000a). Mest hefur verið

sýnt fram á 11 pör af strengjum á lífsskeiði einnar kvenlúsar en að meðaltali eru um 150 egg

í hverjum streng (Heutch o.fl. 2000). Því getur eitt kvenlús framleitt vel yfir 3000 egg á

lífsferli sínum. Lífslíkur minnka þó með hverjum streng sem framleiddur er og aðeins um

25% afkvæma úr síðustu strengjunum ná copepodid stigi (Mustafa o.fl. 2000a).

Eggjaframleiðsla, bæði fjöldi, stærð og lifun fer einnig eftir sjávarhita eins og áður hefur

komið fram.

Til samanburðar líða tæpir 40 dagar við 10°C frá klaki að fyrstu eggjastrengjunum hjá

Sílelúsinni (C. rogercresseyi) en þroskun hennar er einnig háð sjávarhita. Eggjastrengir

hennar innihalda að meðaltali 31 egg sem er töluvert færri en hjá laxalúsinni. Kvenlús

Sílelúsarinnar framleiðir einnig eggjastrengi allt frá því að hún hefur æxlast aðeins einu

sinni og æxlunarfæri hafa náð fullri stærð (Bravo 2010).

6

2.3 Útlit og greining laxa- og grálúsar

Copepodid lirfurnar eru undir 1 mm að stærð, og örlítið stærri hjá laxalús en grálús. Það

sem aðgreinir dýrin helst á þessu stigi eru dældir á hliðum höfuðbols (e. cephalothorax)

grálúsarinnar, milli augans og framenda höfuðbolsins (Schram 2004, Mynd 3).

Mynd 3. Copepodid lirfur laxalúsar (til vinstri) og grálúsar (til hægri). Mælistikur eru 0,1

mm. Samsett mynd frá Scram (2004).

Næsta stig er chalimus I hjá báðum tegundum sem einnig er örlítið stærri hjá laxalúsinni og

nær nú rétt yfir 1 mm. Chalimus I stig laxalúsar sem eiga stutt í næstu hamskipti hafa mælst

allt að 1,5 mm (Hamre o.fl. 2013). Við hamskipti frá copepodid yfir í chalimus I breikkar

einnig líkami lirfunnar og nú er hún föst með einum stilk við hýsilinn en ekki með

gripörmum (Mynd 4). Aðalgreiningaratriði milli tegundanna er enn dæld hjá grálúsinni

svipað og með copepodid lirfuna (Mynd 3). Chalimus I og II eru aðgreind að mestu með

stærð; chalimus II eru yfirleitt yfir 1,5 mm að og geta verið allt að 3 mm rétt fyrir hamskipti

(Hamre o.fl. 2013). Chalimus II hefur einnig lengri þráð að framan og breiðari búk (Mynd

4). Laxalúsinni hefur einnig meiri liðskiptingu á afturbol chalimus II (Schram 1993).

7

Mynd 4. Þroskun laxalúsar frá copepodid að fyrsta forstigi fullorðins stigs (e. pre-adult

I). Kyngreining chalimus stiga var gerð eftir myndum eftir hamskipti lúsa í forstig

fullorðins stigs, slík kyngreining er annars ekki möguleg. Mynd frá Eichner o.fl. (2015).

Grálúsin hefur chalimus III og IV stig og stækkar lirfan við hver hamskipti. Stilkurinn sem

þær festa sig með við hýsilinn lengist einnig við hver hamskipti og búkurinn breikkar auk

þess sem fálmarar verða sýnilegri (Pike o.fl. 1993).

Laxalúsin hefur tvö forstig fullorðinsstigs en grálúsin hefur hamskipti úr lirfustiginu

chalimus IV beint í fullorðins stig og er þá kynþroska. Báðar tegundirnar geta farið að hreyfa

sig um á hýslinum þegar þær hafa hamskipti frá síðasta chalimus lirfustiginu. Á þessu stigi

er fyrst hægt að greina í sundur kynin og er kvenlúsin stærra hjá báðum tegundum.

Kyngreiningar á chalimus stigum hafa verið gerðar á myndum efir að lifandi lýs eiga

hamskipti í forstig fullorðins stigs (Mynd 4). Aftur má sjá breikkun á búk eftir hamskipti og

æxlunarfæri verða greinileg utan um afturendann. Kvenlúsin hefur einskonar knúppa sitt

hvoru megin við þarminn sem mynda M-lagað form en karllúsin hefur kúlulaga æxlunarfæri

sem bólgna út sitt hvoru megin við afturendann (Mynd 2 og Mynd 4). Annað forstig

fullorðinsstigsins (e. pre-adult II) er stærra en það fyrra, æxlunarfæri stækka, eru þroskaðri

og verða oddhvassari í lögun hjá kvenlúsinni. Afturendinn stækkar einnig og fjórði liður

með fótum styttist (Schram 1993).

8

Mynd 5. Grálús, chalimus og fullorðnar kvenlýs ásamt kvenlús með eggjastrengi.

Hálfmánar á höfði sýnilegir © EDJ

Bæði laxalúsin og grálúsin hafa eitt fullorðinsstig þar sem þær verða kynþroska og eiga ekki

hamskipti eftir það. Á þessu stigi er auðvelt að skilja á milli tegundanna. Grálúsin er töluvert

minni, oftast ljósari að lit og hefur einkennandi dældir eins og hálfmána (e. lunule) efst á

höfðinu (Pike o.fl. 1993, Schram 1993, Mynd 5). Æxlunarfæri kvendýrs laxalúsarinnar taka

allt að 2 vikur að þroskast eftir að hún nær þessu stigi á meðan höfuðbolurinn vex ekki meira

(Eichner o.fl. 2008, Mynd 2).

2.4 Áhrif á laxfiska

Fjöldi rannsókna hafa skoðað áhrif lúsa á laxfiska, bæði á lirfustigi (t.d. Grimnes og

Jakobsen 1996, Bowers o.fl. 2000, Tveiten o.fl. 2010) og fullorðinsstigum (t.d. Grimnes og

Jakobsen 1996, Bjørn og Finstad 1997, Nolan o.fl. 1999, Bowers et al. 2000, Wagner er al.

2008), og sýna að áhrif sýkingar aukast til muna þegar um hreyfanlegar lýs er að ræða.

Atlantshafslaxar (Salmo salar), 200-250 g þungir, sýndu líkamleg viðbrögð við sýkingu af

fáum hreyfanlegum laxalúsum (pre-adult og adult). Cortisol (streituhormón) mældist hærra

í blóði laxanna og blóðsykur jókst (Mustafa o.fl. 2000b), fleiri húðfrumur í efsta lagi drápust

(stýrður frumudauði, e. apoptosis) en í viðmiðunarhópum (án sýkingar) og drep myndaðist

á því svæði þar sem lýsnar héldu til. Frumum í slímhúð fækkaði, sem getur haft áhrif á

slímframleiðslu í húð (Nolan o.fl. 1999). Lirfustigin (copepodid og chalimus) hafa mun

minni áhrif á laxinn jafnvel þó þær séu í miklum mæli, en við sýkingu sem samsvaraði 0,2

lirfum á hvert gramm fisks jókst cortisol lítillega í blóði (Bowers o.fl. 2000). En þegar

9

laxalýsnar hafa hamskipti yfir í hreyfanlegu stigin eykst streita hjá fiskum til muna og við

mikla sýkingu getur lúsasýkingin dregið fiskinn til dauða (Grimnes og Jakobsen 1996,

Mustafa o.fl. 2000b, Bowers o.fl. 2000). Rannsóknir á áhrifum Sílelúsarinnar; Gonzáles o.fl.

2016, Vargas-Chacoff o.fl. 2016, sýndu fram á breytingar á blóðsykri, bæði hjá

Atlantshafslaxi og coho-laxi (Oncorhynchus kisutch). Genarannsókn (mRNA) benti einnig

til viðbragða í genum tengdum ónæmiskerfi laxa við sýkingu lirfa Sílelúsarinnar (Boltana

o.fl. 2016). Ætla má að grálúsin hafi sömu eða svipuð áhrif á lax og Sílelúsin.

Rannsókn á bleikju (Salvelinus alpinus) sem átti stutt í að verða kynþroska leiddi einnig í

ljós aukið magn streitu hormóns (cortisol) í blóði við mikla sýkingu laxalúsar (um 0,15 lýs/g

fisks) einkum hjá hrygnum. Enn fremur seinkaði kynþroska og hrognaframleiðsla var minni

í sýktum hrygnum, og mikil sýking leiddi til dauða. Sýking laxalúsar virtist hafa alvarlegri

afleiðingar fyrir hrygnur en hænga, en það voru helst þær sem drápust vegna sýkingar

(Tveiten o.fl. 2010).

Sjávarlýs hafa einnig áhrif á tálkn fiskanna þó svo að þær setjist ekki á þau, en þar koma

fram bólgur og hvít blóðkorn sjást í tálknafönum. Sýking sjávarlúsa hefur því áhrif á

seltujafnvægi fiska (Nolan o.fl. 1999, Costello 2006 og heimildir þar í).

Lýsnar nærast ekki eingöngu á slím, roði og blóði hýsilsins heldur skila þær frá sér

munnvatni sem virkar hemjandi á ónæmiskerfi fisksins (Fast o.fl. 2007, Tadiso o.fl. 2011).

Hreyfanlegar lýs, sem hafa t.d. verið á fiski sýktum af blóðþorra (Infectious Salmon Anemia

virus eða ISA veirunni) bera veiruna með sér (Oelckers o.fl. 2014). Þær geta því smitað aðra

fiska með veirunni og valdið þannig miklum skaða.

Mikið smit laxalúsar á sjóbirtingi á líklega beint og óbeint stóran þátt í miklum afföllum í

stofnum hans (Skaala o.fl. 2013). Hægari vöxtur seiða hefur verið tengdur smiti laxalúsa

(Thorstad o.fl. 2015 og heimildir þar í). Við samanburð á gögnum frá svæðum í Noregi fyrir

og eftir að laxeldi í sjókvíum hófst, kom fram að sjóbirtingar, bæði á fyrsta og öðru ári uxu

hægar eftir að eldið hófst (Fjørtoft o.fl. 2014). Hegðun sjóbirtinga breytist einnig við

lúsasmit. Þeir halda sig fremur nálægt árósum þar sem selta sjávar er minni (Gjelland o.fl.

2014) og ganga í sumum tilfellum fyrr í ferskvatn en ella þegar þeir eru smitaðir af laxalús,

en ganga svo aftur niður þegar þeir eru lausir við smit (Birkeland og Jakobsen 1996,

Gjelland o.fl. 2014). Einnig stökkva sýktir sjóbirtingar meira (Stone o.fl. 2002) og halda sig

nær yfirborðinu (Gjelland o.fl. 2014), og eru því í meiri hættu að verða fyrir afráni en ósýktir

fiskar.

2.5 Sjávarlýs við strendur Íslands

Eldi laxfiska í sjókvíum allt árið um kring veitir laxalúsinni hýsla allt árið, en það hefur sýnt

sig að á svæðum þar sem laxeldi er stundað í sjó eru villt seiði laxfiska meira sýkt í nágrenni

eldis en fjær þeim (Serra-Llinares o.fl. 2014; Thorstad o.fl. 2015; Gargan o.fl. 2016).

Mikilvægi þess að rannsaka villta laxfiska á þeim svæðum sem fiskeldi er fyrirhugað er því

ótvírætt ásamt rannsóknum á allri þeirri villtu náttúru sem getur orðið fyrir áhrifum af

eldinu. Tækifæri til að rannsaka náttúruna áður en áhrifa eldis gætir í miklum mæli hér á

landi er að renna úr greipum. Slíkar rannsóknir munu auka líkur á að hægt sé bregðast við

með markvissari hætti þegar og helst áður en áhrifa gætir. Vestfirðir og aðrir staðir sem

fiskeldi er leyft í sjó á Íslandi veita nú kjörið tækifæri til rannsókna áður en eldið eykst enn

meira.

10

Fylgst hefur verið með smiti laxalúsa á villtum laxfiskum síðustu tvo áratugina í Noregi

(Nilsen o.fl. 2017). Svæði hafa verið friðuð þar fyrir fiskeldi til að vernda villta stofna og

hafa athuganir sýnt að villtir laxfiskar eru minna smitaðir á þeim svæðum (Bjørn og Finstad

2001; Serra Llinares o.fl. 2014). Einhverjar vísbendingar eru einnig um að erfðir hafi

eitthvað með smitálag laxalúsar að gera. Rannsókn þar sem eldislaxar og villtir laxar voru

smitaðir af laxalús sýndi t.d. meira smit á eldislöxum. Þar sem að allir fiskar voru geymdir

í sama keri eru hér vísbendingar um að erfðir hafi eitthvað með smitálag að gera (Glover

o.fl. 2003).

Á Írlandi er einnig fylgst með lúsasmiti á villtum laxfiskum. Nýleg rannsókn þar í landi

sýndi að sjóbirtingur nær eldissvæðum var ekki aðeins meira smitaður heldur var líkamlegt

ástand þeirra einnig verra en á svæðum fjær eldissvæðum (Shephard o.fl. 2016). Rannsókn

í Bresku Kólumbíu í Kanada á smiti laxalúsa á villtum laxfiskum á svæðum þar sem

Atlantshafslax er alinn í sjókvíum og svæðum án fiskeldis leiddi í ljós meira smit í nálægð

við eldi (Saksida o.fl. 2011). Yfirgripsmikil rannsókn var einnig framkvæmd við Írland á

stóru svæði án fiskeldis, þar sem mikilvægra grunnupplýsinga var aflað um náttúrulegt smit

sjávarlúsa á sjóbirtingi. Fram kom nokkuð jafnt smit yfir þrjú ár, þ.e. smit álag mældist það

sama ár eftir ár og sýndi jafnframt hlutfallslega minna smit á svæðum án fiskeldis (Gargan

o.fl. 2016). Það fylgdi þó rannsókninni ekki hver sjávarhiti var yfir þessi þrjú ár en gera má

ráð fyrir að það hafi ekki verið miklar hitabreytingar.

Íslendingar líta mikið til Noregs varðandi áhrif fiskeldis á umhverfið. Hérlendis hafa

rannsóknir á áhrifum laxeldis í sjó hingað til snúið nær eingöngu að vöktunum á botndýralífi

(Eva Dögg Jóhannesdóttir 2016). Nýlega hóf Hafrannsóknarstofnun rannsóknir á

erfðablöndun eldislaxa við villta stofna. Rannsóknin fór fram á Vestfjörðum og kom þar í

ljós merki um erfðablöndun í tveimur vatnsföllum á sunnanverðum fjörðunum (Leó

Alexander Guðmundsson o.fl. 2017).

Lúsasmit á villtum laxfiskum var rannsakað árið 2014 í Arnarfirði, nánar tiltekið utan við

og inni í Fossfirði og Trostansfirði. Annað verkefnið sneri að veiðum á villtum laxfiskum

(aðallega sjóbirtingum) við ströndina og lúsasmit kannað á þeim (Karbowski, 2015). Ekki

fannst marktækur munur á smiti laxfiska sem veiddir voru mjög nálægt eldiskvíum og þeim

sem veiddir voru fjær. Hinsvegar er talið að svæði án áhrifa þurfi að vera í það minnsta yfir

30 km frá fiskeldisvæði (Serra-Llinares o.fl. 2014) og í þessu verkefni voru sýnatökur í

Fossfirði annars vegar og Trostansfirði hins vegar í Arnarfirði. Fiskeldi var stundað í

Fossfirði þegar sýnatökur fóru fram en sjóleiðin inn í Trostanafjörð er innan við 15 km. Í

hinu verkefninu voru laxaseiði frá Fjarðalaxi settir í búr við ströndina í Trostansfirði og

Fossfirði. Lýs voru síðan taldar á þeim þar sem smit mældist meira þar sem laxar voru hafðir

nær eldissvæðum heldur en þeir sem voru fjær. Viðmiðunarstöðin í Trostansfirði sýndi þó

svipað smit og jafnvel meira í einu tilviki (Karbowski, 2015B). Í fyrra verkefninu var

laxalúsin í meirihluta eða um rúmlega 80% af lúsum á fiskum en í því seinna var nær

eingöngu grálús á fiskum. Lúsasmit á villtum laxfiskum var athugað í Ísafjarðardjúpi,

Dýrafirði, Patreksfirði og Tálknafirði árið 2015. Sjókvíaeldi á laxfiskum hafði að einhverju

leyti verið stundað í öllum þeim fjörðum þegar athugunin fór fram, þ.e. eldi á

regnbogasilungi (Oncorhynchus mykiss) í Ísafjarðardjúpi og Dýrafirði en laxeldi í hinum

fjörðunum. Veitt var í júlí og fram í október, en smit laxalúsar kom ekki fram í

Ísafjarðardjúpi fyrr en í ágúst og fór smittíðni laxalúsar hæst í 13%. Í ágúst mældist smit í

Dýrafirði á 10% fiska. Smit mældist alla mánuðina í Patreksfirði (Eva Dögg Jóhannesdóttir

og Jón Örn Pálsson 2016). Í öllum tilfellum var laxalús í miklum meirihluta. Árið 2017 voru

villtir laxfiskar athugaðir á sunnanverðum Vestfjörðum og komu þar fram skýr merki um

11

aukið smit laxalúsar á villtum laxfiskum (aðallega sjóbirtingum) á svæðinu en nánast enga

grálús (sjá kafla 3). Önnur áhrif á náttúru og lífríki í nálægð við eldissvæði hafa ekki verið

rannsökuð. Yfirlitsskýrsla um möguleg áhrif á lífríki og búsvæði í sjó á svæðinu vegna

laxeldis var gefin út árið 2016 (Eva Dögg Jóhannesdóttir 2016). Þar kom fram að helstu

áhrifin gætu orðið á villta laxfiska á svæðinu

Við athuganir á laxi úr kvíum í Arnarfirði árið 2017 kom í ljós að lýs hefðu komið vel undan

vetri, en veturinn 2016-2017 hafði verið óvenju hlýr og sjávarhiti um 2°C heitari en veturinn

áður (Fisksjúkdómanefnd 2017.). Um vorið var því fengið leyfi fyrir lyfjameðhöndlun við

laxalús í Arnarfirði. Meðhöndlað var gegn lús í kvíum í Tálknafirði og Dýrafirði sama ár,

en þar var það C. elongatus sem var til vandræða (Fisksjúkdómanefnd 2017). Árið 2018 olli

laxalúsin tjóni í Tálknafirði og Arnarfirði og var lax þar baðaður með lúsalyfi

(Matvælastofnun 2018).

Mjög mikilvægt er að fylla í það skarð upplýsinga sem er til staðar með frekari athugunum

á lúsasmiti villtra laxfiska áður en eldi eykst meira við strendur Íslands. Þær fáu athuganir

sem farið hafa fram taka ekki á samanburði milli allra fjarða Vestfjarða eða milli villtra fiska

og eldisfiska. Engar athuganir hafa farið fram á svæðum þar sem laxeldi er ekki hafið eða

er bannað. Mikilvægt er að hefja athuganir fljótlega eftir að seiði ganga í sjó. Nauðsynlegt

er að gera heildarathugun í fjörðum þar sem laxeldi er hafið svo hægt sé að bera saman

lúsasmit milli fjarða. Einnig er mikilvægt að slíkum vöktunum verði haldið við og þær

hafnar á öðrum stöðum, t.d. á Austfjörðum þar sem sjókvíaeldi er þegar til staðar. Engar

rannsóknir hafa verið gerðar á þroskun, lifun og fjölgunarhæfni lúsa sem lifa við

Íslandsstrendur.

Heimildir

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13

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Heuch, P. A., Nordhagen, J. R., Schram, T. A. (2000). Egg production in the salmon louse

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parasitic and deters a planktonic copepod. Journal of Planktonic Research, 29:i3-i16

doi:org/10.1093/plankt/fbl060

Hull, M. Q., Pike, A. W., Mordue (Luntz). A. J., Rae, G. H. (1998). Patterns of pair

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challenge for salmon aquaculture. Animal Frontiers 4:22-32. doi:10.2527/af.2014-0004

Imsland, A., Reynolds, P., Eliassen, G., Hangstad, T. A., Foss, A., Vikingstad, E.,

Elvegård, T. A. (2018). The use of lumpfish (Cyclopterus lumpus L.) to control sea lice

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(Salmo salar L.). Aquaculture 424-425: 18-23.

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salmonids in Arnarfjörður, Iceland. Sótt 15. mars 2019, frá

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pacific salmon. Simon Fraser University, pp 70.

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í Tálknafirði og Arnarfirði. Selfossi, 22. júní 2018 18051224.

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15

Mustafa, A., Conboy, G. A., Burka, J. F. (2000a). Life-span and reproductive capacity of

sea lice, Lepeophtheirus salmonis, under laboratory conditions. Aquaculture Association

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16

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infection by salmon louse (Lepeophtheirus salmonis) revealed bi-phasic responses

coinciding with the copepod-chalimus transition. BMC Genomics 12.

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Wadsworth, S. (2016). Atlantic salmon (Salmo salar) and Coho salmon (Oncorhynchus

17

kisutch) dispay differential metabolic changes in response to infestation by the

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salmonis (Krøyer, 1837) on Wild Salmonids. Atlantic Salmon Trust August 2010, pp. 27.

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18

3. Sea lice infestation on wild salmonids in southern part of the

Icelandic Westfjords

3.1. Introduction

Farming of Atlantic salmon (Salmo salar) in sea cages has increased in Iceland over the past

few years. The production went from 3.000 tons in 2015 to 11.000 tons in 2017 and is

estimated to reach 25.000 tons in the year 2020 (Guðfinnsson 2018). This farming takes

place mainly in the Westfjords and Eastfjords of Iceland as other areas are for the most part

closed for salmon farming in sea (Ministry for the Environment and Natural Resources

2004). Salmon farming in sea has grown the most in the south region of Westfjords (Figure

2). The carrying capacity in these fjords is estimated 20.000 tons combined for the fjords

Patreksfjörður and Tálknafjörður (Ólafsdóttir et al. 2015a) and 20.000 tons in Arnarfjörður

(Ólafsdóttir et al. 2015b).

Figure 1. Westfjords; South region marked in a black box © EDJ.

19

Aquaculture has a history in Iceland since the beginning of the 1900s and was at first only

practiced to rear yolk sac larva to stock in rivers. It was first in the 1950s that Icelanders

began experimenting with farming imported rainbow trout (Oncorhynchus mykiss) for

human consumption. Farmed Atlantic salmon smolts were first released in Icelandic coastal

waters in the 1960 as an attempt for ocean ranching which gave little success as a

commercial operation. It was first in the 1980s Icelanders started experimenting with sea-

cage culture, with little success (Guðbergsson & Antonsson 1996). With new enthusiasm,

more funding and knowledge, fish farming began to grow in Iceland late last century,

resulting in considerable rearing of Arctic charr (Salvelinus alpinus) in freshwater tanks on

land and Atlantic salmon in sea cages. Although it was first in the beginning of this century

fish farming in sea cages began in large scale (Landssamband fiskeldisstöðva n. d.).

Salmon farming has been practiced in the South Westfjords since 2010 when smolts were

put in sea cages at Laugardalur site in Tálknafjörður (Teiknistofan Eik, 2016). Such cage

culture was started in Fossfjörður site in Arnarfjörður the next year (Pálsson, 2013) and also

at the site Hlaðseyri in Patreksfjörður in 2012 (Teiknistofan Eik, 2016). Smolts were put in

cages at Haganes in 2014 (Verkís, 2014). In 2017, the company Arnarlax (www.arnarlax.is)

had permits for salmon farming in sea cages at Haganes, Hringsdalur and Steinanes (Figure

2). Salmon was in all farming sites except Hlaðseyri and Tjaldanes in 2017 which were in a

fallowing period (Þóra Jörundsdóttir 15.06.17). Since, aquaculture in sea is still a relative

new industry in Iceland it is important to gather baseline data of the surrounding nature that

can become effected by it.

20

Figure 2. Salmon farming in south region of the Westfjords in 2017. Hlaðseyri in

Patreksfjörður, Laugardalur in Tálknafjörður and Haganes, Steinanes, Hringsdalur and

Tjaldanes in Arnarjförður marked with a black triangle © EDJ.

There are considerable environmental issues concerning aquaculture in sea cages (e.g.

Costello 2006, Holmer et al. 1992, Taranger et al. 2011). Knowledge of the farming sites

and surroundings, as well as the ecosystems that are influenced is of great importance for

conservation and management. Indeed, negative environmental impact of aquaculture can

harm the aquaculture production itself, e.g. by increasing growth of undesirable organisms.

Organic enrichment because of waste (feces and excess feed) from aquaculture can have

various effects including impact on both wildlife and habitat, triggering of toxic blooms and

demise of wild fish stocks (Mente et al. 2006). Blooms of microalgae can do damage to fish

inside and outside of sea cages (Heisler et al. 2008 and references therein). Furthermore,

waste and excess feed that sinks to the ocean floor can cause enrichment of the benthos

under and close to farming sites (Holmer et al. 2003). This effects bottom dwelling

organisms and can cause decreased biodiversity and in extreme cases kill organisms that

have a vital role in decomposition by aerobic processes. This can sometimes lead to an

increase in anaerobic bacteria that may take over the decomposition process and release

21

undesirable gasses which in some cases can be poisonous (Holmer & Kristensen 1992;

Holmer et al. 2003).

Another environmental issue concerning aquaculture, especially in sea cages, is escape of

farmed fish. Farmed fish can reproduce with local wild stocks and such genetic mixing has

been of major concern (e.g. Naylor et al. 2005), e.g. because it can lower survival rate and

reduce fitness of wild fish (McGinnity et al. 1997, 2003, 2009; Reed et al. 2015).

Experiments indicate that smolt production decreases in wild stocks in areas with escaped

farmed fish or mixed individuals (Fleming et al. 2000, McGinnity et al. 2009). Newly

conducted research has shown changes to life-history traits in salmon after wild salmon

breeding with escaped farmed salmon (Bolstad et al. 2017). This can result in irreversible

loss of diversity in wild fish and loss of small and sensitive wild populations (Glover et al.

2017).

Last but not least is the issue of increased infection rate of both parasites and diseases in

areas of sea-based aquaculture (e.g. Costello 2009; Brauner et al. 2012; Thorstad et al. 2015

and references therein). A major concern is an increase of sea lice; Lepeophtheirus salmonis

commonly known as the salmon louse and Caligus elongatus. Heavy infection on cultured

salmon can have great financial impact on farming companies where the main species of

concern has been L. salmonis (e.g. Jansen et al. 2012); C. elongatus can also be of major

concern, e.g. in Scotland (Revie 2002, Treasurer and Bravo 2011). C. elongatus is closely

related to Caligus rogercresseyi (Treasurer and Bravo 2011) which has been a major issue

in Chilean salmon farming (Bravo 2003, Johnson et al. 2004, Treasurer and Bravo 2011).

Fish farmers of Atlantic salmon in the Westfjords have experienced an increase in C.

elongatus infestation. One company registered on average 120 C. elongatus per fish

examined in the fall of 2017 which forced it to use emamectin benzoate (Slice) in November

2017 to de-lice the salmon (Unpublished data from the farming companies Arnarlax and

Arctic Sea Farm). Slice is mixed in with the feed and given orally to the salmon and has

shown good results removing mobile lice as well as preventing molting of the larvae stages

(Stone et al. 2002). This treatment is not without problems. For example, studies on L.

salmonis and C. rogercresseyi have shown less sensitivity to the treatment if it is applied

frequently (Helgesen & Horsberg 2013, Jones et al. 2012, Agusti et al. 2016), and non-target

crustaceans can be negatively affected by it (i.e. Veldhoen et al. 2012, Daoud et al. 2018).

Both L. salmonis and C. elongatus are found on wild fish but with aquaculture they get

access to high number of hosts (i.e. farmed fish) and in more density than in nature as well

as access to hosts all year around (e.g. Costello 2006; Costello 2009 and references therein).

whilst wild salmonids can and will mostly migrate up freshwater streams in fall. Sea trout

(Salmo trutta sea-run brown trout) migrates to sea in early spring and back to freshwater

streams in late summer and fall after a summer at sea, where they probably stay close to

their natal river but are also known to travel long distances, for example from south to north

Norway (Jonson et al. 1995). Atlantic salmon stocks in Iceland generally spend one or two

years at sea. It has been shown that during winter salmon from west of Iceland can be found

in the ocean where temperatures are close to 8°C (Kristinsson et al. 2015). Icelandic salmon

has been caught as far as West Greenland and north of the Faroe Islands. Arctic charr is

different in its anadromy as all individuals return to freshwater every year. The species also

stays for the shortest time in sea of the three salmonid species found in Iceland and

presumably stays close to its natal river (Guðbergsson & Antonsson 1996, Klementsen et

al. 2003). With large scale salmon aquaculture in the sea cages, sea lice can increase their

22

reproductive rate and thus infest both wild and farmed fish with more intensity (e.g. Costello

2006; Costello 2009 and references therein).

It has been shown, that wild salmonids in areas of salmonid aquaculture in sea are more

infested with sea lice than those without aquaculture (Serra-Llinares, 2014; Thorstad et al.

2015; Gargan et al., 2016). It is therefore considered important to monitor these infestations

in countries with salmonid aquaculture. Sea lice infestation has for example been monitored

in Norway, Ireland and Canada (British Colombia) where areas with and without salmonid

aquaculture in sea have been compared (Bjørn og Finstad 2002, Serra-Llinares et al. 2014,

Gargan et al. 2016, Shepard et al. 2016). In Norway, infestations have been monitored for

over 20 years (Nilsen et al. 2017) and protected areas have been designated where salmonid

aquaculture is forbidden in sea (Serra-Llinares et al. 2014). The monitoring program in

Norway is extensive and in collaboration with the Norwegian government, scientist have

made a system to assess possible effect on wild salmonid populations. It is a traffic light

system where they use green, yellow and red to indicate whether populations are not affected

by infestations, moderately effected or greatly affected. If an area is red lighted the farming

companies are to reduce production, yellow light is neutral and green light means the

companies have the possibility to increase production in the area (Anon 2018).

A few studies have been conducted on sea lice in general in Icelandic coastal waters, all

focusing on the Westfjords in Iceland. Karbowski (2015a) examined sea lice infestation on

wild salmonids by catching them in gill-nets located in Trostansfjörður (Figure 2).

Furthermore, Karbowski (2015b) studied infestation rate with non-infested Atlantic salmon

in sentinel cages in Trostansfjörður. These two projects were both conducted in July and

August 2014 and gave quite different results. In the first one the main salmonid species

caught was sea trout and they were mainly infested with salmon lice with C. elongatus

representing only about 12% of all lice found throughout the project. In the second project

C. elongatus was almost the only species registered on the caged salmon with salmon lice

representing close to 1% of all lice found. Jóhannesdóttir & Pálsson (2016) found that

salmon lice were also the more abundant species on wild salmonids with C. elongatus

representing about 1% of all lice found.

The objective of this project is to contribute to the knowledge of sea lice infestation on wild

salmonids in the southern part of the Westfjords; providing baseline knowledge on the wild

fish before sea cage culture of Atlantic salmon grows further in the area. This is important

for future research and monitoring programs on aquaculture impact in the area and for

Iceland in general.

23

The specific goals are to:

1. Examine and register sea lice infection on wild salmonids in the coastal waters of

the south region of the Westfjord peninsula, considering the following research

questions:

a. What sea lice species is most common in the area and at what time?

b. Is there a difference in infection between the fjords in the region?

c. Does infection rate increase over the summer months and does sea lice

species composition change?

d. Has infection increased from earlier observations in the area?

2. Compare observations of sea lice infestation on salmon in sea cages and on wild fish

in the area considering the following research question:

a. Is there a difference in infection between farmed fish and wild fish in the

area?

3. To increase information of salmonid distribution in the area, considering the

following research questions:

a. What salmonid species is most common in the coastal waters of the area?

b. Is there a difference in species composition among the fjords?

3.2 Materials and methods

Sea lice infestation on wild salmonids was examined in Westfjords south region. Salmonids

were caught in gill nets on pre-selected sites in the area (Figure 3). Selection of sampling

sites was made with consideration of earlier projects (Karbowski 2015a, Jóhannesdóttir and

Pálsson 2016), e.g. for later comparison of findings.

Sampling was conducted in three fjords: Patreksfjörður, Tálknafjörður and Arnarfjörður

(Figure 3). Sites sampled in Patreksfjordur were in Ósafjörður and in Skápadalur where the

rivers Ósá and Skápadalsá are located. Sampling sites in Tálknafjörður were at Eysteinseyri

and Hvammeyri close to the estuary of river Botnsá in Norðurbotn. Sampling sites in

Arnarfjörður were in Trostansfjörður close to the estuaries of Norðdalsá and Sunndalsá

(Figure 3).

24

Figure 3. Research area in two sites in Patreksfjörður (Blue), Tálknafjörður (Green) and

Arnarfjörður (Blue and red).

Permission from land owners was acquired as well as research permit from the Directorate

of Fisheries to acquire exemption from law 61/2006, which restricts fishing for migrating

trout with nets at the coast line, from 22:00 hours on Fridays until 10:00 hours on Tuesdays.

As sampling with gill-nets is dependent on weather as well as tidal movements it was

important to get these excemtions and permits.

Two samplings were conducted in Patreksfjörður and three in Tálknafjörður and

Arnarfjörður. First of the samplings in all fjords are named sampling 1, second sampling 2

and the last one sampling 3. Sampling began at the end of June in Tálknafjörður and in the

beginning of July in Arnarfjörður and Patreksfjörður. In Arnarfjörður and Patreksfjörður

sampling 1 was made over 2 days (Table 1).

Vesturbotn

25

Table 1. Dates of samplings in the three fjords.

Sampling Tálknafjörður Arnarfjörður

Patreksfjörður

1

05.07.17

09.07.17

29.06.17 07.07.17 12.07.17

2 26.07.17

28.07.17

30.07.17

3 05.09.17

10.09.17

Gill-nets with mesh size of 16, 21, 26 and 35 mm were used to catch the fish. All nets were

25 m in length and reached 2 m in depth except for the 16 mm which was 30 m and 1.5 m

deep. On each end was a float attached to the end of the floating line and a weight on the

end of the sink line (Figure 4).

Nets were laid perpendicular to land as close to the time of low tide as possible each time.

Sampling was carried out from low to high tide and nets checked regularly throughout the

sampling time. Sampling was stopped when 30 fish were caught or in some cases because

of unfavorable weather conditions or equipment failure. Each fish was put in separate plastic

bag marked with number, sampling site and date for later examination on land.

Figure 4. Net deployment in sea, dimensions are not to scale. Figure © EDJ.

Ocean temperature and salinity were measured at the surface (10 cm), and at 1 m and 2 m

depth with a Multiline P4 gauge at each site and sampling time

Fish were species identified in a laboratory, and each individual placed in a white plastic

tray with freshwater covering the whole fish. For location of sea lice, they were examined

under a lamp with a magnifying glass. The water moves immobile larvae so their posterior

floats upwards while they are still attached with their anterior part. The plastic bags were

also examined for lice that might have fallen off fishes. In cases of high numbers of larvae

attached to fins, fins were cut off for further examination and more careful removal of larvae

under a stereoscope. Lice were preserved in an 70% ethanol solution.

26

Fish were weighed and fork length (FL) measured from the tip of the snout to middle of the

caudal fin. Two to three gill filaments were cut from each fish and preserved in 70% ethanol

for possibilities of genetic analysis. Samples of scales, from the left posterior side of each

fish, and otoliths were taken and placed in a paper bag. Stomachs were removed, put in a

marked plastic bag and frozen for possibilities of later analysis.

Sea lice species were identified under a stereoscope. Identifications were based on Schram

(2004) and Eichner et al (2008, 2015). Photographs of lice specimens were sent to a

specialist (Sussie Dalvin) at the Norwegian Institute for Marine Research that confirmed

correct identification, both of species and different stages in life cycle.

Identification was made of different stages in the lice life cycle. Larvae stages that are

fastened to the hosts body and mobile stages that are able to move around on the host body.

The first larva stage is the copepodid which is the stage the lice infests fish and then molts

to chalimus I and later to chalimus II. C. elongatus has two more chalimus stages; III and

IV. Salmon lice molt from chalimus II to the mobile stage of pre-adult I and then further to

pre-adult II and finally the last stage: adult. C. elongatus molts from chalimus IV to adult.

In their mobile stage both species can be identified by sex. A decision was made to only

make identification on chalimus stages without differentiating between the different stages

as well as pre-adult stages. Infection pressure should be considered the same from one

chalimus stage to the next as well as pre-adult stage to the next. Pre-adults were identified

for L. salmonis and divided in to male and female. Adults for both species were identified

and divided in to male and female as well as females with attached egg strings were

registered specially. Identifying different stages of life cycles is important data as it shows

development of generations in time and allows for predictions of infection patterns.

To assess infestation rate, prevalence (percentage of fish infested), mean abundance (mean

number of lice on all fish) and mean intensity (mean number of lice on infected fish only)

was calculated for each sampling at each site. Kruskal-Wallis and Man-Whitney’s U-test as

recommended by Rótza et al. (2000) was used to compare intensities between fjords with

p-value < 0,05. Box and whiskers charts were made do depict prevalence, abundance and

intensity (Thorstad et al. 2015, Nilsen et al. 2017). Boxes show the interquartile range and

a median value and whiskers showing the maximum and minimum values.

The effect of infestation on salmonids was assessed using the methods recommended by the

Scientific Council in Norway (Anon 2018). For sea trout and Arctic charr it has been

recommended to estimate this separately for first time migrants to sea (<150 g) and more

mature (>150 g) individuals (Tveiten et al. 2010). Therefore, there are different models used

for the two groups (<150 and > 150), as recommended by Taranger et al. (2012), which the

Scientific council of Norway uses (Anon 2018) as well as the Food Safety Authorities of

Norway (Mattilsynet 2017). Schema for calculation of population effect for these two

groups are as given in Taranger et al. (2012) and are shown in Table 2 for fish under 150 g

and in Table 3 for fish over 150 g. For example, the schema in Table 2 is to be filled out

with data from lice counting. Proportion of population (%) that have <0.1 lice/g per fish will

all survive (0% deaths), 20% of fish with 0.1-0.2 lice/g will die, 50% will die with infestation

of 0.2-0.3 lice/g and 100% of fish with 0.3>lice/g will die. “Proportion of population (%)”

multiplied with “Death of population (%)” gives the index number. Estimated reduction is

the sum of the index numbers. Table 3 works in the same way only with different

parameters.

27

Table 2. A schema for estimating population effect made for Arctic charr and sea trout

first time migrant to sea <150 g.

Number of lice per gram fish

Portion of population

Death of population Index

< 0.1 0% 0.1-0.2 20% 0.2-0.3 50% >0.3 100% Estimated reduction of population

Table 3. A schema for estimating population effect made for mature Arctic charr and

sea trout >150 g.

Number of lice per gram fish

Portion of population

Death of population Index

< 0.025 0% 0.025-0.05 20% 0.05-0.1 50% 0.1-0.15 75% >0.15 100%

Estimated reduction of population

Small effect is estimated for populations if the estimated reduction of population (total of

index) is under 10% (green light), a moderate effect if it’s 10-30% (yellow light) and a great

effect if it exceeds 30% (red light) (Taranger et al. 2012). It should be noted that this is a

method developed for Norwegian conditions and has not been adjusted in any way for

Icelandic conditions.

Infestation of sea lice on wild salmonids was compared with infestation on farmed salmon

in the area with data from all lice countings in sea cages from the company Arnarlax. Lice

are counted on salmon once a month when sea temperatures are over 4°C and ambient

temperature is over 5°C all year around except June to October where lice are counted every

other week. Counting is performed in half of the cages each time; if the area has 12 cages,

counting is performed in 6 of them. About 20 fish or more are taken from each cage, sedated

and carefully examined and counting and identification registered. The company counts

mobile lice (not larvae), registers different species and counts females with egg strings for

L. salmonis only. It is therefore only possible to make a comparison of these stages between

the farmed fish and wild fish.

28

3.3 Results

In all 158 fish were caught in all samplings in 2017. With the exception of four Arctic charr

(Salvelinus alpinus) caught in Tálknafjörður and two pink salmon (Oncorhynchus

gorbuscha) in Patreksfjörður, all fish were sea trout (Salmo trutta)

Over half (54%) of all the fish were caught in a net with 21 mm mesh, 36% were caught in

26 mm and 9% in 16 mm (see details in Appendix 1 and Appendix 2).

Sea salinity at sampling sites were measured lowest at the surface in all fjords. The lowest

salinity (14.9‰) was observed in Tálknafjörður. Deeper measurements of salinity were

always over 30‰ with one exception in Tálknafjörður where salinity was measured 29.4‰

at one meter but was over 33‰ at 2 m depth. Surface temperature ranged from 10.8°C -

13°C in Patreksfjörður, 9.5°C – 15.4°C in Tálknafjörður and 9.6°C – 11.7°C in Arnarfjörður

(see details in Appendix 3).

Mean weight of the 16 fish caught in Patreksfjörður was 650 g with mean length of 330 mm.

Of the 75 salmonids caught in Tálknafjörður the mean weight was 167 g and mean length

240 mm. Mean weight of the 65 fish caught in Arnarfjörður was 113 g with mean length of

220 mm (Table 4).

Table 4. Mean weight (g) and length (mm) of salmonids (Arctic charr and sea trout)

from all samplings and locations with standard deviation (SD) and range from smallest to largest.

Patreksfjörður

Sampling N

Mean

weight SD Range

Mean

length SD Range

1 8 629 703 60-1924 321 13.2 171-514

2 8 669 697 83-1760 340 12.4 197-510

Total 16 650 330

Tálknafjörður

Sampling N

Mean

weight SD Range

Mean

length SD Range

1 14 223 197 41-636 260 6.4 162-405

2 26 150 11 13-646 220 90.0 104-375

3 35 160 64 32-335 240 111.0 144-300

Total 75 167 240

Arnarfjörður

Sampling N

Mean

weight SD Range

Mean

length SD Range

1 15 146 131 48-499 220 4.6 190-336

2 34 87 55 25-293 190 3.0 126-288

3 16 134 62 74-320 220 2.9 190-300

Total 65 113 210

29

3.3.1 Sea lice parameters

Prevalence of all L. salmonis was lowest in the first sampling and became higher with each

sampling reaching 100% in the last samplings in all fjords (Figure 5).

C. elongatus was only present in Arnarfjörður in sampling 1 and was not observed in

sampling 2 except in Patreksfjörður on two pink salmon (Oncorhynchus gorbuscha). C.

elongatus was observed in Tálknafjörður and Arnarfjörður in the last samplings. Highest

prevalence of C. elongatus in Patreksfjörður was 25%.

Figure 5. Prevalence of L. salmonis in all areas over the research period. Blue is

Tálknafjörður, orange is Arnarfjörður and gray Patreksfjörður.

Mean abundance of L. salmonis in Tálknafjörður was 3.5, 5 and 27.5 in sampling 1-3

respectively, in Arnarfjörður it was 18.6, 6.7 and 13.7 for the three samplings and in

Patreksfjörður 74.5 and 30.4 for the two samplings there (Figure 6).

Mean intensity for in Tálknafjörður for L. salmonis was 8.2, 5.2 and 27,5 for sampling 1-3

respectively, in Arnarfjörður 19.9, 7.1 and 13.7 for the three samplings in Patreksfjörður

85.1 and 40.5 for the two samplings there (Figure 7).

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

1 2 3

Infe

sted

fis

h (

%)

Samplings

Prevalence L. salmonis

Tálknafjörður

Arnarfjörður

Patreksfjörður

30

Figure 6. L. salmonis abundance in Patreksfjörður, Tálknafjörður and Arnarfjörður for samplings 1 (blue), 2 (red) and 3 (green). Boxes show the interquartile range,

horizontal line the median, x marks the mean abundance, whiskers maximum and minimum values and points outliers. Note different values in y-axis for Patreksfjörður

(pink box).

Figure 7. L. salmonis intensity in Patreksfjörður, Tálknafjörður and Arnarfjörður for

samplings 1 (blue), 2 (red) and 3 (green). Boxes show the interquartile range,

horizontal line the median, x marks the mean abundance, whiskers maximum and minimum values and points outliers. Note different values in y-axis for Patreksfjörður

(pink box).

Assessment of population effect in the three locations showed a great effect would be

expected on the population in Patreksfjörður throughout all samplings with about 50% loss

in the population in both samplings. However, this is calculated from a very small number

of fish (2-5 fish). In Tálknafjörður infection showed little effect on the population in the first

sampling but progressed to great effect in the last sampling with an estimate of 81% loss of

fish over 150 g. Great effect was calculated for fish under 150 g in Arnarfjörður in the first

sampling with the fish over 150 showing small effect (3 fish). Otherwise the population in

Arnarfjörður had a moderate effect from lice except for fish over 150 g in the last sampling

with estimated loss of 61% (Table 5).

31

Table 5. Assessment of population effect in all locations over all samplings.

Calculations are based on recommendations from Taranger et al. (2012) for both fish

under 150 g and over 150 g. Green = small effect (<10%), yellow = moderate effect (10-30%), red = great effect (>30%).

Sampling 1 Sampling 2 Sampling 3

N < 150 N >150 N < 150 N >150 N < 150 N >150

Patreksfjörður 2 50% 5 48% 2 35% 4 48%

Tálknafjörður 6 3% 8 9% 17 5% 9 22% 17 31% 18 81%

Arnarfjörður 12 43% 3 7% 32 11% 2 25% 12 19% 4 61%

Threshold for significance was set at p < 0,05 for statistical tests. Considering all L.

salmonis, comparison of all locations using Kruskal-Wallis test showed significant

difference between the three locations in sampling 1 and 2 (p = 0,040 and <0,001). A Man-

Whitney test revealed no significant difference between Tálknafjörður and Arnarfjörður for

the first two samplings (p = 0,090 and 0,110) but significant difference in the last sampling

(p = 0,008). Statistical analysis was not made for C. elongatus as sample sizes were too

small.

3.3.2 Different lice stages

L. salmonis were found in all parasitic stages with the first two non-mobile stages being

found through all samplings. Pre-adults were also found in all samplings in all fjords. Adult

females were not found in Tálknafjörður and Arnarfjörður in sampling 1 but seven adult

males were found in Arnarfjörður. Gravid females appeared in sampling 2 in all fjords. C.

elongatus appeared in Patreksfjörður in sampling 2 and gravid females were only

represented there. C. elongatus was only found on pink salmon in that location. C. elongatus

first appeared in Tálknafjörður and Arnarfjörður in sampling 3. Differences in abundance

were sometimes great between locations as well as samplings which made it difficult to use

the same scales for each graph (Figure 8).

32

Figure 8. Different life stages of L. salmonis and C. elongatus in all locations and

samplings. Each graph is marked with location, Tálknafjörður (Tálkn), Arnarfjörður (Arn) and Patreksfjörður (Patr) and number for period. Graphs start out with L. salmonis

copepodid (Cop), Chalimus I and II (Chal), Preadult F I and II (PreF), Preadult M (PreM),

adult females (F), adult males (M), gravid females are represented as orange in the pillar for females. Last three pillars to right are for C. elongatus: Chalimus I, II, III and

IV (Chal), adult female (F) and adult male (M), gravids as L. salmonis. Note the different

scale on the y-axis between samples 1, 2 and 3 and for Patreksfjörður.

Distribution of life stages show development over the samplings. Larvae represent the

largest part of sample 1 in all locations with later stages being more represented in sampling

2 and larvae becoming more prominent in sampling 3 (Figure 9).

33

Figure 9. Distribution of life stages depicted as frequency of whole sample from

sampling 1-3 in all locations.

3.3.3 Lice counts from Arnarlax

C. elongatus was the most abundant species of sea lice on salmon in sea cages in the south

of the Westfjords during the research period. With an exception in July where L. salmonis

became a little more abundant than C. elongatus in Arnarfjörður. C. elongatus had the

highest abundance in all sea cages in September with over 7 lice/fish registered in Hlaðseyri

(Patreksfjörður), 5 lice/fish in Tálknafjörður and 3,4 lice/fish in one location in Arnarfjörður

the two other locations in Arnarfjörður had very low abundancies of both species. With such

differences in abundance the scales on the graphs could not be set to the same values (Figure

10). The only location in Arnarfjörður with fish in cages over the winter 2016-2017 was

Hringsdalur. In this location L. salmonis was in high abundance until spring with up to 8,72

female L. salmonis per fish recorded in late April. This resulted in de-liceing in May.

Salmon in cages in Tálknafjörður and Patreksfjörður did not experience such high

infestation of L. salmonis during the winter and spring with highest abundance of females

in Tálknafjörður registered 0,1 in May and 0,62 in Patreksfjörður.

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Tálkn 1 Tálkn 2 Tálkn 3 Arn 1 Arn 2 Arn 3 Patr 1 Patr 2

Fre

qu

enc

y

Distribution of life stage - L. salmonis

Male

Pre-Male

Female

Pre-Female

Chalimus

Copepodid

34

Figure 10. Sea lice abundance in Arnarlax’s farming areas in Arnarfjörður: Hringsdalur,

Haganes, Steinanes, in Patreksfjörður: Hlaðseyri and in Tálknfjörður: Laugardalur. Note

the different scale on the y-axis.

35

3.4 Discussion

The most common species of sea lice on wild salmonids in this study was Lepeophtheirus

salmonis. Only a few Caligus elongatus were found and in September only. However, C.

elongatus was also found on pink salmon in July, which had probably migrated from far

away.

When comparing infestation on wild salmonids in Tálknafjörður and Arnarfjörður a

significant difference was found in sampling 3 considering L. salmonis. Thus, the

abundancy of larval stages in Tálknafjörður was over three times as high as in Arnarfjörður.

This shows different infestation pressure between the two fjords. It has been shown that

areas without salmonid farming in sea cages tend to display same intensity and prevelance

year after year (Gargan et al. 2016) although sea temperature has not been reported. High

larval count in Tálknafjörður cannot be directly connected with lice counting in cages in the

area since almost no L. salmonis were found there (Figure 9, Figure 10). Without monitoring

of wild salmonids in this area it will be difficult to show further development in infestation

pressure. Infestation pressure from L. salmonis is clearly far higher on wild salmonids than

on farmed fish whereas the farmed fish are mostly infested by C. elongatus.

Larvae are more abundant in sample 1 compared to sample 2 in all locations. This is

consistent with lice developing into later stages as has been seen in other studies (Bjørn &

Finstad 2002, Gargan et al. 2016, Nilsen et al. 2017). Comparing to Bjørn & Finstad (2002),

who did a comparison of infections on wild salmonids in areas with and without salmonid

aquaculture in sea cages, the development of life stages in this study resembles their area

without aquaculture. The area without aquaculture showed higher frequency of larvae

throughout the research period than with aquaculture. Gravid females first appear in the

second sampling in all locations, and in Tálknafjörður and Arnarfjörður there is a

considerable increase in larva counts in the last sampling. This is consistent with eggs being

produced in the period of the first sampling and maturing to chalimus stage in the time

between samplings. Egg would probably have hatched in less than 10 days and developed

into copepodid within two days in the sea temperatures reigstered during the sampling

period (Boxaspen & Næss 2000).

Comparing my results from Arnarfjörður with the previous project conducted in 2014

(Karbowski N 2014), the first obvious differences is less infection of C. elongatus in 2017

on wild caught fish. However, L. salmonis has become considerably more abundant on wild

salmonids in 2017. Overall, infestation of L. salmonis has increased both in abundance and

intensities, with highest mean abundance recorded 7.5 in 2014 and highest mean intensities

7.9, calculated for both L. salmonis and C. elongatus (Karbowski 2014), compared to 18.6

for only L. salmonis in abundance and intensity of 19.9 in 2017. What is also interesting is

that C. elongatus was the most abundant species on the farmed salmon smolts kept in cages

(Karbowski CM 2014). The present results show a difference between infestation on farmed

salmon and wild trout which needs be investigated further.

Assessment of the effects of L. salmonis infestation on wild populations in these areas show

moderate to high effects in sampling two and three in Tálknafjörður and Arnarfjörður (Table

5). Thus, there is an estimated loss of the populations because of lice infestation that is

considered moderate (10-30% death of population) or high (over 30% death). Earlier studies

did not show any effect on wild populations (Karbowski 2015a, Jóhannesdóttir & Pálsson

36

2016). This is evidence of, that not only is there and increase in L. salmonis in the areas, but

the infestation pressure is beginning to have an impact on the wild populations. This kind

of assessments are used in Norway to control salmonid production in sea and are therefore

correlated directly with the aquaculture production. If high effect on wild populations is

observed, fish farm production in that area are to be reduced (Anon 2018, Taranger et al.

2012). Natural infestation pressure from L. salmonis can be high enough to kill salmonids

without aquaculture (Torrissen et al. 2013). L. salmonis is the main species on fish in sea

cages in Norway (i.e. Taranger et al. 2012, Nilsen et al. 2017) whereas C. elongatus was the

main species in Icelandic sea cages in 2017. This should be taken into consideration in future

monitoring programs in Iceland.

Sea temperature is an important factor in L. salmonis development and survival, with lower

survival of eggs and unsuccessful development to infectious stages at temperatures below

2°C (Boxaspen & Næss 2000, Samsing et al. 2016). It is therefore important to consider that

sea temperatures were considerably higher on average over the winter months of 2016-2017

in Arnarfjörður, staying well above 2°C, compared to around 1°C in the three previous years

(Pálsson 2018). The rise in sea temperatures between years could have affected the

reproduction and faster development of L. salmonis. L. salmonis did show high infestation

in Arnarfjörður in the winter 2016-2017, possibly due to higher sea temperetures

(Matvælastofnun 2017). There is evidence of acclimation in L. salmonis to colder waters

(Costello 2006), as lice from north Norway seem to have better success reproducing in

colder waters than lice in south Norway (Boxaspen & Næss 2000, Samsing et al. 2016). It

is therefore a possibility that L. salmonis in Iceland are acclimated to colder waters than in

Norway, and thus have more success reproducing in such conditions.

Sea trout (Salmo trutta) was the dominant species in the sampling areas. Only four Arctic

charr (Salvelinus alpinus) were caught in Tálknafjörður and two pink salmon in

Patreksfjörður. Even though Atlantic salmon were reported in the rivers close to the

sampling sites in Tálknafjörður and in Trostansfjörður in Arnarfjörður in the two previous

years (Einarsson & Ólafsson 2016, Guðmundsson et al. 2017) they were not caught in the

present study. Given what is known about these salmonid species’ life histories it is most

likely that the salmon smolt migrated to open sea whereas the trout and charr stayed close

to their home river and foraged in the intertidal range (Guðbergsson & Antonsson 1996).

Low number of Arctic charr was caught in the present study and all of them in

Tálknafjörður. The species was last documented in River Botnsá in 2014 (Þórisson 2014).

In retrospect, poor catches in Patreksfjörður were to be expected as River Ósá was reported

completely void of salmonids in 2015, whereas sea trout has been abundant in a river further

out and closer to the mouth of the fjord (Einarsson & Ólafsson 2016).

It was surprising to catch the nonnative pink salmon in Patreksfjörður. The same summer

pink salmon was caught in Norway, UK and Faroe Islands. It is most likely that they

originate from White sea and Kola Peninsula rivers in Russia. Such straying has been

observed in Norway since the 1950s where spawning pink salmon have also been reported

(Mo et al. 2018). Why there is this sudden outburst in migration of the species in 2017 can

likely be contributed to especially favorable conditions for spawning and feeding in the

ocean (Mo et al. 2018). In 2017 there were 54 pink salmon caught in Iceland and among

those some ripe females (Þórðardóttir & Guðbergsson 2018).

37

3.5 Conclusions

Sea lice infestation on wild salmonids is obviously increasing in the southern Westfjords,

were higher sea temperatures may play a role. With low numbers of L. salmonis infections

of salmon in sea cages in the areas it is difficult relate growing infestations on wild

salmonids directly to increased farming. Thus, it remains unclear why infestation rate on

wild salmonids in these areas has increased. It is imperative that a monitoring program is

set afoot in order to document and study infestations on wild salmonids because aquaculture

in sea cages in likely to increase and also that climate change, affecting sea temperatures,

might continue. The increase in infestation on wild salmonids from earlier research and the

estimation that the infestation rate in 2017 is having negative effect on the wild salmonid

populations is unsettling, considering that there is no ongoing research at this time or

monitoring programs. It is of great importance to monitor wild populations as well as

making comparison to farmed fish. An assessment system for popultion effect could be

useful and should be adjusted to Icelandic conditions. Farmed salmon in the area have much

greater infection rate of C. elongates compared to the wild sea trout which is mostly infected

by L. salmonis. Farming companies should therefore focus more on C. elongatus than they

do today with more detailed monitoring of gravid females of the species. Off course it will

also be important to consider infestations of L. salmonis on farmed salmon.

More research on the distribution and abundance of wild salmonids is needed in the

Westfjords. We also need much more research on sea lice in Iceland. For example, little is

known about sea lice reproduction and survival in Icelandic coastal waters which reach close

to 0°C in winter. Little is known about the biology of sea lice at such low temperatures.

Lowest ocean temperatures in Finnmark county of Norway, where sea cage culture of

salmon is common, has been at minimum 2,2°C, and does usually not go below 3°C

(seatemperature.org). Distribution of sea lice larvae around Iceland is unknown and no

observations have been made outside the Westfjords. It is important to start a monitoring

program of sea lice infections on wild salmonids in all Icelandic coastal waters, both where

salmonids are farmed in sea cages and in other areas, to gather knowledge of the status today

as well as obtaining a clear picture of the development of infestation. This is essential both

as Iceland is now growing rapidly as a producer of Atlantic salmon in sea cages, and also

because of ongoing climate change.

38

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under laboratory conditons. Aquatic Toxicoly 108, 94-105

Verkís. (2014). Aukning framleiðslu Arnarlax á laxi í sjókvíum í Arnarfirði um 7.000 tonn

á ári. Mat á umhverfisáhrifum – Frummatsskýrsla.

Þórðardóttir, G., Guðbergsson, G. (2018), Lax- og silungaveiði 2017. Haf- og

vatnarannsóknir, Marine and freshwater research in Iceland. Reykajvík, June 2018. HV

2018-35, pp. 36.

Þórisson, B. (2014). Athugun á búsvæðum og seiðabúskap í Botnsá í Norðurbotni í

Tálknafirði. NV nr. 11-14.

44

Appedixes

Appendix 1. Net deployments and catches in Arnarfjörður for all periods.

Arnarfjörður

Period 1 Period 2 Period 3

Net Catch Catch Catch Total fish Frequency

16 mm

0%

21 mm

0%

26 mm

0%

21 mm 1

1 1%

26 mm

0%

26 mm 2

2 3%

21 mm 8

8 12%

21 mm 4 8 1 13 19%

16 mm

0%

26 mm

17 12 29 43%

21 mm

7

7 10%

26 mm

4

4 6%

26 mm

3 3 4%

Total fish 15 36 16 67 100%

45

Appendix 2. Net deployments and catches in Tálknafjörður for all samplings.

Tálknafjörður

Sampl 1 Sampl 2 Sampl 3

Net Catch Catch Catch Total fish Frequency

16 mm 3

3 4%

16 mm

8 1 9 12%

21 mm 1

1 1%

26 mm 2

2 3%

21 mm

4 18 22 29%

35 mm

0 0%

26 mm

4 6 10 13%

21 mm 6 8 9 23 31%

26 mm 2 2 1 5 7%

Total fish 14 26 35 75 100%

Appendix 3. Environmental measurements in all locations June to September.

Patreksfjörður

Point: Ósafjörður 1 Ósafjörður 2 Skápadalur

Sampl Depth °C Sal °C Sal °C Sal

1

10 cm 12.5 27.7 10.8 32.8

1 m 11.7 30.7 10.8 33.2

2 m 11.0 32.4 10.8 33.5

2

10 cm 13.0 32.5 12.3 33.4 12.7 34.0

1 m 12.5 33.7 12.4 33.4 12.7 34.0

2 m 12.4 33.8 12.5 33.5 12.6 34.0

46

Tálknafjörður

Point: T01 T02 T03 T04 T05 T06

Period Depth °C Sal °C Sal °C Sal °C Sal °C Sal °C Sal

1

10 cm 9.5 14.9 9.5 29.2

1 m

2 m

2

10 cm 15.2 20.0 15.4 19.5 12.6 31.2

1 m 12.3 29.4 12.1 30.2 12.0 32.0

2 m 10.8 33.5 10.4 33.4 11.1 33.4

3

10 cm 10.6 24.6 10.9 30.2 10.7 24.6

1 m 10.8 31.1 10.9 30.4 10.8 30.6

2 m 10.9 31.3 10.9 31.9 10.9 32.0

Arnarfjörður

Point: A06 A08 A11 A13 A09/A14 A15

Trip Depth °C Sal °C Sal °C Sal °C Sal °C Sal °C Sal

1

10 cm 9.6 33.4 10.7 32.0

1 m 9.4 33.6 9.4 33.5

2 m 9.3 33.6 9.3 33.6

2

10 cm 11.5 32.9 11.7 33.6 11.0 25.0

1 m 11.4 33.8 11.7 33.6 11.4 33.7

2 m 11.3 33.8 11.6 33.7 11.4 33.8

3

10 cm 10.0 31.7 10.2 34.0

1 m 10.2 32.2 10.3 33.9

2 m 10.4 33.8 10.3 34.0

All temperature measurements are in degrees in Celsius and salinity in ‰