Canadian Tax Dollars going to good use...fish farm bailouts...
- Thread starter Andrew P
- Start date
Stand-by CK: it's coming your way. I deliberately omitted grey literature, thesis work, and peer-reviewed work on the effects of lice (physiologically) on fish. I figured we could all agree on those effects w/o much controversy. REMEMBER: this is peer-reviewed work on only 1 aspect of negative consequences of the open net-pen industry. Benthic impacts, impacts of escapees and inbreeding, fish health and disease transfers, and impacts of the feed industry (as 4 other examples) are not covered in these papers.
Parasitology (1999), 119, 41±51. Printed in the United Kingdom # 1999 Cambridge University Press
Spatial and temporal variation in the infestation of sea trout (Salmo trutta L.) by the caligid copepod Lepeophtheirus salmonis (Krùyer) in relation to sources of infection in Ireland
O. TULLY"*, P. GARGAN#, W. R. POOLE$ and K. F. WHELAN$
" Department of Zoology, Trinity College Dublin, Dublin 2, Ireland
# Central Fisheries Board, Mobhi Boreen, Balnahowan, Glasnevin, Dublin 9, Ireland
$ Salmon Research Agency, Furnace, Newport, Co. Mayo, Ireland
(Received 26 October 1998; revised 28 January 1999; accepted 28 January 1999)
Summary
Infestations of post-smolt sea trout (Salmo trutta L.) by the salmon louse (Lepeophtheirus salmonis Krùyer) were characterized in 42 estuaries over a 5 year period in Ireland. Spatial variation in infestation was more significant than temporal trends and existed at 3 levels ; between regions (regions"100 km of coastline), between bays within regions (bays! 50 km in length) and between estuaries within bays (distance between estuaries!10 km). The observed spatial structure in infestations inferred that production of the infective larvae varied between regions and bays and that there was limited movement of fish and infective larvae between regions and bays. In addition the different levels of infestation recorded between estuaries in the same bay indicated short spatial scale variability in parasite transmission. Significantly higher infestations occurred in bays that contained lice-infested farmed salmon. Lice-infested wild spring salmon, which were present in estuaries of some systems, did not have a significant positive impact on infestations.
Key words: salmon louse, sea trout, spatial structure, infestation.
Spatial and temporal variation in the infestation of sea trout (Salmo trutta L.) by the caligid copepod Lepeophtheirus salmonis (Krùyer) in relation to sources of infection in Ireland
O. TULLY"*, P. GARGAN#, W. R. POOLE$ and K. F. WHELAN$
" Department of Zoology, Trinity College Dublin, Dublin 2, Ireland
# Central Fisheries Board, Mobhi Boreen, Balnahowan, Glasnevin, Dublin 9, Ireland
$ Salmon Research Agency, Furnace, Newport, Co. Mayo, Ireland
(Received 26 October 1998; revised 28 January 1999; accepted 28 January 1999)
Summary
Infestations of post-smolt sea trout (Salmo trutta L.) by the salmon louse (Lepeophtheirus salmonis Krùyer) were characterized in 42 estuaries over a 5 year period in Ireland. Spatial variation in infestation was more significant than temporal trends and existed at 3 levels ; between regions (regions"100 km of coastline), between bays within regions (bays! 50 km in length) and between estuaries within bays (distance between estuaries!10 km). The observed spatial structure in infestations inferred that production of the infective larvae varied between regions and bays and that there was limited movement of fish and infective larvae between regions and bays. In addition the different levels of infestation recorded between estuaries in the same bay indicated short spatial scale variability in parasite transmission. Significantly higher infestations occurred in bays that contained lice-infested farmed salmon. Lice-infested wild spring salmon, which were present in estuaries of some systems, did not have a significant positive impact on infestations.
Key words: salmon louse, sea trout, spatial structure, infestation.
Proc. R. Soc. B published online 7 November 2012
doi: 10.1098/rspb.2012.2359
Impact of parasites on salmon recruitment in the Northeast Atlantic Ocean
Martin Krkosˇek1, Crawford W. Revie2, Patrick G. Gargan3, Ove T. Skilbrei4,
Bengt Finstad5 and Christopher D. Todd6
1Department of Zoology, University of Otago, Dunedin, New Zealand
2Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Canada
3Inland Fisheries Ireland, Dublin, Ireland
4Institute of Marine Research, Bergen, Norway
5Norwegian Institute for Nature Research, Trondheim, Norway
6Scottish Oceans Institute, University of St Andrews, St Andrews, UK
Parasites may have large effects on host population dynamics, marine fisheries and conservation, but a clear elucidation of their impact is limited by a lack of ecosystem-scale experimental data. We conducted a meta-analysis of replicated manipulative field experiments concerning the influence of parasitism by crustaceans on the marine survival of Atlantic salmon (Salmo salar L.). The data include 24 trials in which tagged smolts (totalling 283 347 fish; 1996–2008) were released as paired control and parasiticide-treated groups into 10 areas of Ireland and Norway. All experimental fish were infection free when released into freshwater, and a proportion of each group was recovered as adult recruits returning to coastal waters 1 or more years later. Treatment had a significant positive effect on survival to recruitment, with an overall effect size (odds ratio) of 1.29 that corresponds to an estimated loss of 39 per cent (95% CI: 18–55%) of adult salmon recruitment. The parasitic crustaceans were probably acquired during early marine migration in areas that host large aquaculture populations of domesticated salmon, which elevate local abundances of ectoparasitic copepods—particularly Lepeophtheirus salmonis. These results provide experimental evidence from a large marine ecosystem that parasites can have large impacts on fish recruitment, fisheries and conservation.
doi: 10.1098/rspb.2012.2359
Impact of parasites on salmon recruitment in the Northeast Atlantic Ocean
Martin Krkosˇek1, Crawford W. Revie2, Patrick G. Gargan3, Ove T. Skilbrei4,
Bengt Finstad5 and Christopher D. Todd6
1Department of Zoology, University of Otago, Dunedin, New Zealand
2Atlantic Veterinary College, University of Prince Edward Island, Charlottetown, Canada
3Inland Fisheries Ireland, Dublin, Ireland
4Institute of Marine Research, Bergen, Norway
5Norwegian Institute for Nature Research, Trondheim, Norway
6Scottish Oceans Institute, University of St Andrews, St Andrews, UK
Parasites may have large effects on host population dynamics, marine fisheries and conservation, but a clear elucidation of their impact is limited by a lack of ecosystem-scale experimental data. We conducted a meta-analysis of replicated manipulative field experiments concerning the influence of parasitism by crustaceans on the marine survival of Atlantic salmon (Salmo salar L.). The data include 24 trials in which tagged smolts (totalling 283 347 fish; 1996–2008) were released as paired control and parasiticide-treated groups into 10 areas of Ireland and Norway. All experimental fish were infection free when released into freshwater, and a proportion of each group was recovered as adult recruits returning to coastal waters 1 or more years later. Treatment had a significant positive effect on survival to recruitment, with an overall effect size (odds ratio) of 1.29 that corresponds to an estimated loss of 39 per cent (95% CI: 18–55%) of adult salmon recruitment. The parasitic crustaceans were probably acquired during early marine migration in areas that host large aquaculture populations of domesticated salmon, which elevate local abundances of ectoparasitic copepods—particularly Lepeophtheirus salmonis. These results provide experimental evidence from a large marine ecosystem that parasites can have large impacts on fish recruitment, fisheries and conservation.
Can. J. Fish. Aquat. Sci. 67: 1925–1932 (2010) doi:10.1139/F10-105 Published by NRC Research Press
Evidence of farm-induced parasite infestations on wild juvenile salmon in multiple regions of coastal British Columbia, Canada
M.H.H. Price, A. Morton, and J.D. Reynolds
Abstract: Salmon farms are spatially concentrated reservoirs of fish host populations that can disrupt natural salmonid host–parasite dynamics. Sea lice frequently infect farm salmon and parasitize sympatric wild juvenile salmonids, with negative impacts on survival in Europe and Pacific Canada. We examined louse parasitism of wild juvenile chum salmon (Oncorhynchus keta) and pink salmon (Oncorhynchus gorbuscha) from three salmon farming regions in British Columbia (Finlayson, Broughton Archipelago, and Georgia Strait). We compared sites of low and high exposure to farms and included an area without farms (Bella Bella) to assess baseline infection levels. Louse prevalence and abundance were lowest and most similar to natural baseline levels at low-exposure sites and highest at high-exposure sites in all farm regions. A significantly greater proportion of the lice were Lepeophtheirus salmonis at high-exposure sites. Exposure to salmon farms was the only consistently significant factor to explain the variation in prevalence data, with a secondary role played by salinity. Our results support the hypothesis that salmon farms are a major source of sea lice on juvenile wild salmon in salmon farming regions and underscore the importance of using management techniques that mitigate threats to wild stocks.
Evidence of farm-induced parasite infestations on wild juvenile salmon in multiple regions of coastal British Columbia, Canada
M.H.H. Price, A. Morton, and J.D. Reynolds
Abstract: Salmon farms are spatially concentrated reservoirs of fish host populations that can disrupt natural salmonid host–parasite dynamics. Sea lice frequently infect farm salmon and parasitize sympatric wild juvenile salmonids, with negative impacts on survival in Europe and Pacific Canada. We examined louse parasitism of wild juvenile chum salmon (Oncorhynchus keta) and pink salmon (Oncorhynchus gorbuscha) from three salmon farming regions in British Columbia (Finlayson, Broughton Archipelago, and Georgia Strait). We compared sites of low and high exposure to farms and included an area without farms (Bella Bella) to assess baseline infection levels. Louse prevalence and abundance were lowest and most similar to natural baseline levels at low-exposure sites and highest at high-exposure sites in all farm regions. A significantly greater proportion of the lice were Lepeophtheirus salmonis at high-exposure sites. Exposure to salmon farms was the only consistently significant factor to explain the variation in prevalence data, with a secondary role played by salinity. Our results support the hypothesis that salmon farms are a major source of sea lice on juvenile wild salmon in salmon farming regions and underscore the importance of using management techniques that mitigate threats to wild stocks.
Mortality of Seaward-Migrating Post-smolts of Atlantic Salmon Due to Salmon Lice Infection in Western Norwegian Salmon Stocks
Jens Christian Holst1, Per Jakobsen2, Frank Nilsen1, Marianne Holm1,
Lars Asplin1, and Jan Aure1
1Institute of Marine Research,
P.O. Box 1870, N-5817 Bergen, Norway
2University of Bergen,
P.O. Box 7800, N-5020 Bergen, Norway.
Keywords: Post-smolt Atlantic salmon, salmon lice, infection, mortality
Since the early 1990s premature returns due to heavy salmon lice infections have been observed in Norwegian sea trout stocks. Following these observations it was hypothesized that salmon lice could also cause serious problems and mortality for seaward-migrating salmon post-smolts. However, due to the direct migration into the high seas of this species, evidence was hard to secure. In 1998 the Institute of Marine Research, Bergen, Norway in cooperation with the University of Bergen initiated fjordic surveys aimed at estimating the level of salmon lice infection in seaward-migrating post-smolts of western Norwegian salmon stocks and the impact of these infections on their survival. Through the development of a live-capture trawl device, Ocean-Fish-Lift, it has been possible to secure live samples of post-smolt salmon without removing any lice from the fish. Sampling of post-smolts has also taken place in the open ocean later in the season when the salmon lice have grown to their most aggressive stages. It has also been possible to run a controlled experiment to estimate the mortal level of salmon lice infection on wild salmon post-smolts. The mean infection levels of copepodites and chalimus stages have been observed to vary from 0 to 104 per fish between years and fjords. The hydrographic features of the specific fjord and year seem to be major factors governing the infection level. The controlled experiment suggested a mortal level of 11 adult salmon lice on wild post-smolts. This number is in close accordance with the oceanic observations, where no salmon taken during a period of 10 years were observed to carry more than 10 adult salmon lice in July. Based on the observed infection levels and a conservative mortal limit of 15 adult salmon lice, estimates of up to 95% mortality due to salmon lice infection have been observed. Although the reported mean numbers of adult female lice in fish farms in the area studied have been reduced to close to the allowed level of 0.5 adult females per fish in the spring, salmon lice still appear to be a problem for many wild salmon stocks in western Norway. In particular, rivers draining into the heads of long fjords seem to be adversely affected. As it seems unrealistic that salmon lice levels in fish farms will be further reduced in the near future, an additional measure for critically affected rivers would be to treat the smolts with a protective chemical against salmon lice infection during the migration to sea.
Jens Christian Holst1, Per Jakobsen2, Frank Nilsen1, Marianne Holm1,
Lars Asplin1, and Jan Aure1
1Institute of Marine Research,
P.O. Box 1870, N-5817 Bergen, Norway
2University of Bergen,
P.O. Box 7800, N-5020 Bergen, Norway.
Keywords: Post-smolt Atlantic salmon, salmon lice, infection, mortality
Since the early 1990s premature returns due to heavy salmon lice infections have been observed in Norwegian sea trout stocks. Following these observations it was hypothesized that salmon lice could also cause serious problems and mortality for seaward-migrating salmon post-smolts. However, due to the direct migration into the high seas of this species, evidence was hard to secure. In 1998 the Institute of Marine Research, Bergen, Norway in cooperation with the University of Bergen initiated fjordic surveys aimed at estimating the level of salmon lice infection in seaward-migrating post-smolts of western Norwegian salmon stocks and the impact of these infections on their survival. Through the development of a live-capture trawl device, Ocean-Fish-Lift, it has been possible to secure live samples of post-smolt salmon without removing any lice from the fish. Sampling of post-smolts has also taken place in the open ocean later in the season when the salmon lice have grown to their most aggressive stages. It has also been possible to run a controlled experiment to estimate the mortal level of salmon lice infection on wild salmon post-smolts. The mean infection levels of copepodites and chalimus stages have been observed to vary from 0 to 104 per fish between years and fjords. The hydrographic features of the specific fjord and year seem to be major factors governing the infection level. The controlled experiment suggested a mortal level of 11 adult salmon lice on wild post-smolts. This number is in close accordance with the oceanic observations, where no salmon taken during a period of 10 years were observed to carry more than 10 adult salmon lice in July. Based on the observed infection levels and a conservative mortal limit of 15 adult salmon lice, estimates of up to 95% mortality due to salmon lice infection have been observed. Although the reported mean numbers of adult female lice in fish farms in the area studied have been reduced to close to the allowed level of 0.5 adult females per fish in the spring, salmon lice still appear to be a problem for many wild salmon stocks in western Norway. In particular, rivers draining into the heads of long fjords seem to be adversely affected. As it seems unrealistic that salmon lice levels in fish farms will be further reduced in the near future, an additional measure for critically affected rivers would be to treat the smolts with a protective chemical against salmon lice infection during the migration to sea.
North American Journal of Fisheries Management 25:811–821, 2005
q Copyright by the American Fisheries Society 2005
DOI: 10.1577/M04-149.1
Temporal Patterns of Sea Louse Infestation on Wild Pacific Salmon in Relation to the Fallowing of Atlantic Salmon Farms
ALEXANDRA MORTON*
Raincoast Research, Simoom Sound, British Columbia V0P 1S0, Canada
RICHARD D. ROUTLEDGE
Department of Statistics and Actuarial Science, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada
ROB WILLIAMS
Raincoast Conservation Society, Pearse Island, British Columbia V0N 1A0, Canada
Abstract.—We report on a 3-year study of the infestation rates of the sea louse, Lepeophtheirus salmonis, on wild juvenile pink salmon Oncorhynchus gorbuscha and chum salmon O. keta in the Broughton Archipelago, British Columbia. In 2002, the British Columbia Ministry of Agriculture, Fisheries, and Food ordered farm fallowing (i.e., the removal of farmed Atlantic salmon Salmo salar from net-cages) along the presumed migration route of wild juvenile Pacific salmon in this area. The goal was to protect wild juvenile fish from sea louse infestation. We assessed the effectiveness of this decision by comparing sea louse infestation rates on wild juvenile salmon near three Atlantic salmon farm sites prior to, during, and after fallowing. Overall, L. salmonis levels were significantly reduced (P , 0.0001) at the study sites during fallowing but returned to the original level after fallowing. The decline was age specific. While the abundance of the earliest attached sea louse phase (the copepodid stage) declined by a factor of 42, the mean abundance of adult L. salmonis did not decline significantly. Changes in salinity and temperature could not account for the decline. This study provides evidence that the fallowing of Atlantic salmon farms during spring juvenile salmon migrations can be an effective conservation and management tool for protecting wild salmon. While this correlation adds to the increasing weight of evidence linking Atlantic salmon farms to increased parasite loads on wild salmon, greater cooperation between researchers and farmers will be necessary to isolate the causal mechanisms and provide safe seaward passage to wild juvenile salmon
q Copyright by the American Fisheries Society 2005
DOI: 10.1577/M04-149.1
Temporal Patterns of Sea Louse Infestation on Wild Pacific Salmon in Relation to the Fallowing of Atlantic Salmon Farms
ALEXANDRA MORTON*
Raincoast Research, Simoom Sound, British Columbia V0P 1S0, Canada
RICHARD D. ROUTLEDGE
Department of Statistics and Actuarial Science, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada
ROB WILLIAMS
Raincoast Conservation Society, Pearse Island, British Columbia V0N 1A0, Canada
Abstract.—We report on a 3-year study of the infestation rates of the sea louse, Lepeophtheirus salmonis, on wild juvenile pink salmon Oncorhynchus gorbuscha and chum salmon O. keta in the Broughton Archipelago, British Columbia. In 2002, the British Columbia Ministry of Agriculture, Fisheries, and Food ordered farm fallowing (i.e., the removal of farmed Atlantic salmon Salmo salar from net-cages) along the presumed migration route of wild juvenile Pacific salmon in this area. The goal was to protect wild juvenile fish from sea louse infestation. We assessed the effectiveness of this decision by comparing sea louse infestation rates on wild juvenile salmon near three Atlantic salmon farm sites prior to, during, and after fallowing. Overall, L. salmonis levels were significantly reduced (P , 0.0001) at the study sites during fallowing but returned to the original level after fallowing. The decline was age specific. While the abundance of the earliest attached sea louse phase (the copepodid stage) declined by a factor of 42, the mean abundance of adult L. salmonis did not decline significantly. Changes in salinity and temperature could not account for the decline. This study provides evidence that the fallowing of Atlantic salmon farms during spring juvenile salmon migrations can be an effective conservation and management tool for protecting wild salmon. While this correlation adds to the increasing weight of evidence linking Atlantic salmon farms to increased parasite loads on wild salmon, greater cooperation between researchers and farmers will be necessary to isolate the causal mechanisms and provide safe seaward passage to wild juvenile salmon
Proc. R. Soc. B
doi:10.1098/rspb.2007.1122
Published online
Effects of host migration, diversity and aquaculture on sea lice threats to Pacific salmon populations
Martin Krkosˇek1,*, Allen Gottesfeld2, Bart Proctor3, Dave Rolston3,
Charmaine Carr-Harris3 and Mark A. Lewis1
1Centre for Mathematical Biology, Departments of Mathematical and Statistical Sciences and Biological Sciences,
University of Alberta, Edmonton, Alberta, Canada T6G 2G1
2Skeena Fisheries Commission, Hazelton, British Columbia, Canada V0J 1Y0
3Oona River Resources Association, Oona River, British Columbia, Canada V0V 1E0
Animal migrations can affect disease dynamics. One consequence of migration common to marine fish andinvertebrates is migratory allopatry—a period of spatial separation between adult and juvenile hosts, which is caused by host migration and which prevents parasite transmission from adult to juvenile hosts. We studied this characteristic for sea lice (Lepeophtheirus salmonis and Caligus clemensi ) and pink salmon (Oncorhynchus gorbuscha) from one of the Canada’s largest salmon stocks. Migratory allopatry protects juvenile salmon from L. salmonis for two to three months of early marine life (2–3% prevalence). In contrast, host diversity facilitates access for C. clemensi to juvenile salmon (8–20% prevalence) but infections appear ephemeral. Aquaculture can augment host abundance and diversity and increase parasite exposure of wild juvenile fish. An empirically parametrized model shows high sensitivity of salmon populations to increased L. salmonis exposure, predicting population collapse at one to five motile L. salmonis per juvenile pink salmon. These results characterize parasite threats of salmon aquaculture to wild salmon populations and show how host migration and diversity are important factors affecting parasite transmission in the oceans.
Keywords: migration; host diversity; parasite transmission; aquaculture; salmon; sea lice
doi:10.1098/rspb.2007.1122
Published online
Effects of host migration, diversity and aquaculture on sea lice threats to Pacific salmon populations
Martin Krkosˇek1,*, Allen Gottesfeld2, Bart Proctor3, Dave Rolston3,
Charmaine Carr-Harris3 and Mark A. Lewis1
1Centre for Mathematical Biology, Departments of Mathematical and Statistical Sciences and Biological Sciences,
University of Alberta, Edmonton, Alberta, Canada T6G 2G1
2Skeena Fisheries Commission, Hazelton, British Columbia, Canada V0J 1Y0
3Oona River Resources Association, Oona River, British Columbia, Canada V0V 1E0
Animal migrations can affect disease dynamics. One consequence of migration common to marine fish andinvertebrates is migratory allopatry—a period of spatial separation between adult and juvenile hosts, which is caused by host migration and which prevents parasite transmission from adult to juvenile hosts. We studied this characteristic for sea lice (Lepeophtheirus salmonis and Caligus clemensi ) and pink salmon (Oncorhynchus gorbuscha) from one of the Canada’s largest salmon stocks. Migratory allopatry protects juvenile salmon from L. salmonis for two to three months of early marine life (2–3% prevalence). In contrast, host diversity facilitates access for C. clemensi to juvenile salmon (8–20% prevalence) but infections appear ephemeral. Aquaculture can augment host abundance and diversity and increase parasite exposure of wild juvenile fish. An empirically parametrized model shows high sensitivity of salmon populations to increased L. salmonis exposure, predicting population collapse at one to five motile L. salmonis per juvenile pink salmon. These results characterize parasite threats of salmon aquaculture to wild salmon populations and show how host migration and diversity are important factors affecting parasite transmission in the oceans.
Keywords: migration; host diversity; parasite transmission; aquaculture; salmon; sea lice
Ecological Applications, 21(3), 2011, pp. 897–914
! 2011 by the Ecological Society of America
Fish farms, parasites, and predators: implications for salmon population dynamics
MARTIN KRKOSˇEK,1,2,7 BRENDAN M. CONNORS,3 HELEN FORD,4 STEPHANIE PEACOCK,4 PAUL MAGES,3 JENNIFER S. FORD,5 ALEXANDRA MORTON,6 JOHN P. VOLPE,4 RAY HILBORN,2 LAWRENCE M. DILL,3 AND MARK. A. LEWIS 1
1Centre for Mathematical Biology, Department of Biological Sciences and Department of Mathematical and Statistical Sciences,
University of Alberta, Edmonton, Alberta T6G 2G1 Canada
2School of Aquatic and Fishery Sciences, University of Washington, Seattle, Washington 98105 USA
3Earth to Ocean and Evolutionary and Behavioural Ecology Research Groups, Department of Biological Sciences,
Simon Fraser University, Burnaby, British Columbia V5A 1S6 Canada
4School of Environmental Studies, University of Victoria, Victoria, British Columbia V8W3R4 Canada
5Biology Department, Dalhousie University, Halifax, Nova Scotia B3H4J1 Canada
6Salmon Coast Field Station, Simoom Sound, British Columbia V0P 1S0 Canada
Abstract. For some salmon populations, the individual and population effects of sea lice (Lepeophtheirus salmonis) transmission from sea cage salmon farms is probably mediated by predation, which is a primary natural source of mortality of juvenile salmon. We examined how sea lice infestation affects predation risk and mortality of juvenile pink (Oncorhynchus gorbuscha) and chum (O. keta) salmon, and developed a mathematical model to assess the implications for population dynamics and conservation. A risk-taking experiment indicated that infected juvenile pink salmon accept a higher predation risk in order to obtain foraging opportunities. In a schooling experiment with juvenile chum salmon, infected individuals had increased nearest-neighbor distances and occupied peripheral positions in the school. Prey selection experiments with cutthroat trout (O. clarkii ) predators indicated that infection reduces the ability of juvenile pink salmon to evade a predatory strike. Group predation experiments with coho salmon (O. kisutch) feeding on juvenile pink or chum salmon indicated that predators selectively consume infected prey. The experimental results indicate that lice may increase the rate of prey capture but not the handling time of a predator. Based on this result, we developed a mathematical model of sea lice and salmon population dynamics in which parasitism affects the attack rate in a type II functional response. Analysis of the model indicates that: (1) the estimated mortality of wild juvenile salmon due to sea lice infestation is probably higher than previously thought; (2) predation can cause a simultaneous decline in sea louse abundance on wild fish and salmon productivity that could mislead managers and regulators; and (3) compensatory mortality occurs in the saturation region of the type II functional response where prey are abundant because predators increase mortality of parasites but not overall predation rates. These findings indicate that predation is an important component of salmon–louse dynamics and has implications for estimating mortality, reducing infection, and developing conservation policy.
Key words: aquaculture; behavior; fish farms; Lepeophtheirus salmonis; Oncorhynchus spp.; parasites; population dynamics; predation; salmon; sea lice.
! 2011 by the Ecological Society of America
Fish farms, parasites, and predators: implications for salmon population dynamics
MARTIN KRKOSˇEK,1,2,7 BRENDAN M. CONNORS,3 HELEN FORD,4 STEPHANIE PEACOCK,4 PAUL MAGES,3 JENNIFER S. FORD,5 ALEXANDRA MORTON,6 JOHN P. VOLPE,4 RAY HILBORN,2 LAWRENCE M. DILL,3 AND MARK. A. LEWIS 1
1Centre for Mathematical Biology, Department of Biological Sciences and Department of Mathematical and Statistical Sciences,
University of Alberta, Edmonton, Alberta T6G 2G1 Canada
2School of Aquatic and Fishery Sciences, University of Washington, Seattle, Washington 98105 USA
3Earth to Ocean and Evolutionary and Behavioural Ecology Research Groups, Department of Biological Sciences,
Simon Fraser University, Burnaby, British Columbia V5A 1S6 Canada
4School of Environmental Studies, University of Victoria, Victoria, British Columbia V8W3R4 Canada
5Biology Department, Dalhousie University, Halifax, Nova Scotia B3H4J1 Canada
6Salmon Coast Field Station, Simoom Sound, British Columbia V0P 1S0 Canada
Abstract. For some salmon populations, the individual and population effects of sea lice (Lepeophtheirus salmonis) transmission from sea cage salmon farms is probably mediated by predation, which is a primary natural source of mortality of juvenile salmon. We examined how sea lice infestation affects predation risk and mortality of juvenile pink (Oncorhynchus gorbuscha) and chum (O. keta) salmon, and developed a mathematical model to assess the implications for population dynamics and conservation. A risk-taking experiment indicated that infected juvenile pink salmon accept a higher predation risk in order to obtain foraging opportunities. In a schooling experiment with juvenile chum salmon, infected individuals had increased nearest-neighbor distances and occupied peripheral positions in the school. Prey selection experiments with cutthroat trout (O. clarkii ) predators indicated that infection reduces the ability of juvenile pink salmon to evade a predatory strike. Group predation experiments with coho salmon (O. kisutch) feeding on juvenile pink or chum salmon indicated that predators selectively consume infected prey. The experimental results indicate that lice may increase the rate of prey capture but not the handling time of a predator. Based on this result, we developed a mathematical model of sea lice and salmon population dynamics in which parasitism affects the attack rate in a type II functional response. Analysis of the model indicates that: (1) the estimated mortality of wild juvenile salmon due to sea lice infestation is probably higher than previously thought; (2) predation can cause a simultaneous decline in sea louse abundance on wild fish and salmon productivity that could mislead managers and regulators; and (3) compensatory mortality occurs in the saturation region of the type II functional response where prey are abundant because predators increase mortality of parasites but not overall predation rates. These findings indicate that predation is an important component of salmon–louse dynamics and has implications for estimating mortality, reducing infection, and developing conservation policy.
Key words: aquaculture; behavior; fish farms; Lepeophtheirus salmonis; Oncorhynchus spp.; parasites; population dynamics; predation; salmon; sea lice.
North American Journal of Fisheries Management 27:000–000, 2007
Copyright by the American Fisheries Society 2007
DOI: 10.1577/M06-043.1
Estimated Sea Louse Egg Production from Marine Harvest
Canada Farmed Atlantic Salmon in Broughton Archipelago,
British Columbia, 2003–2004
CRAIG ORR*
Watershed Watch Salmon Society, Coquitlam, British Columbia V3K 3B7, Canada
Abstract.—Recent infestations of sea lice Lepeophtheirus salmonis on wild juvenile pink salmon Oncorhynchus gorbuscha and subsequent declines in the number of returning adult pink salmon have raised concern for the health of wild fish relative to salmon farming activities in the Broughton Archipelago, British Columbia. I used available (but limited) industry data to estimate sea louse egg production from Atlantic salmon Salmo salar farmed by Stolt Sea Farm (now Marine Harvest Canada, Inc., Campbell River, British Columbia) in 2003 and 2004. The 12 active farms contained between 1 and 5 million Atlantic salmon during the 2 years and about 800,000 fewer mature salmon at the start of 2003 than in 2004. Sea louse egg production peaked during winter–spring in both years prior to the seaward migration period of the area’s small and vulnerable juvenile pink salmon and chum salmon O. keta. Marine Harvest Canada salmon hosted over 6 million gravid sea lice that produced 1.63109 eggs during 2 weeks in the winter of 2003–2004. Only half as many eggs were produced from the fewer hosts present during this period in 2003. Sea lice on farmed fish were further reduced to near zero each year through multiple uses of emamectin benzoate (Slice). Fewer farmed Atlantic salmon and sea lice in 2003 coincided with lower abundance and prevalence of L. salmonis on juvenile pink salmon and chum salmon near farms. A recent agreement between industry and conservationists may help improve data quality, our understanding of the dynamics sea louse–salmon interactions, and our chances of conserving wild salmon.
Copyright by the American Fisheries Society 2007
DOI: 10.1577/M06-043.1
Estimated Sea Louse Egg Production from Marine Harvest
Canada Farmed Atlantic Salmon in Broughton Archipelago,
British Columbia, 2003–2004
CRAIG ORR*
Watershed Watch Salmon Society, Coquitlam, British Columbia V3K 3B7, Canada
Abstract.—Recent infestations of sea lice Lepeophtheirus salmonis on wild juvenile pink salmon Oncorhynchus gorbuscha and subsequent declines in the number of returning adult pink salmon have raised concern for the health of wild fish relative to salmon farming activities in the Broughton Archipelago, British Columbia. I used available (but limited) industry data to estimate sea louse egg production from Atlantic salmon Salmo salar farmed by Stolt Sea Farm (now Marine Harvest Canada, Inc., Campbell River, British Columbia) in 2003 and 2004. The 12 active farms contained between 1 and 5 million Atlantic salmon during the 2 years and about 800,000 fewer mature salmon at the start of 2003 than in 2004. Sea louse egg production peaked during winter–spring in both years prior to the seaward migration period of the area’s small and vulnerable juvenile pink salmon and chum salmon O. keta. Marine Harvest Canada salmon hosted over 6 million gravid sea lice that produced 1.63109 eggs during 2 weeks in the winter of 2003–2004. Only half as many eggs were produced from the fewer hosts present during this period in 2003. Sea lice on farmed fish were further reduced to near zero each year through multiple uses of emamectin benzoate (Slice). Fewer farmed Atlantic salmon and sea lice in 2003 coincided with lower abundance and prevalence of L. salmonis on juvenile pink salmon and chum salmon near farms. A recent agreement between industry and conservationists may help improve data quality, our understanding of the dynamics sea louse–salmon interactions, and our chances of conserving wild salmon.
AQUACULTURE ENVIRONMENT INTERACTIONS
Aquacult Environ Interact
Vol. 1: 137–146, 2010
doi: 10.3354/aei00014
Published online December 21
Dynamics of outbreak and control of salmon lice on two salmon farms in the Broughton Archipelago, British Columbia
Martin Krkoˇsek1, 4,*, Andrew Bateman2, Stan Proboszcz3, Craig Orr3
1School of Aquatic and Fishery Science, University of Washington, Seattle, Washington 98105, USA
2Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, UK
3Watershed Watch Salmon Society, Coquitlam, British Columbia V3K 3B7, Canada
4Present address: Department of Zoology, University of Otago, Dunedin 9016, New Zealand
ABSTRACT: Outbreaks of parasitic salmon lice Lepeoptheirus salmonis in sea-cage salmon farming regions of coastal seas have challenged the productivity of salmon farming industries and the conservation of wild salmon. We used a simple mathematical model to evaluate the population ecology of louse outbreaks, parasiticide treatment, and louse population decline for 2 farms in the Broughton Archipelago region of British Columbia, Canada. Results suggest that exponential population growth of lice within a farm, rather than sustained louse immigration from wild sources, drive outbreaks on farms. Model analysis indicates that louse infection pressure from farms to wild juvenile salmon may be minimized by parasiticide application 2 to 3 mo preceding the juvenile salmon outmigration. The observed timing of parasiticide use and population decline of lice on farms is consistent with reported declines of lice on wild juvenile salmon. If parasiticides do not have adverse environmental effects and lice do not evolve resistance, optimized parasiticide use on salmon farms may help reduce the spread of lice to wild salmon populations.
KEY WORDS: Salmon • Sea lice • Aquaculture • Parasite • Outbreak • Eradication
Aquacult Environ Interact
Vol. 1: 137–146, 2010
doi: 10.3354/aei00014
Published online December 21
Dynamics of outbreak and control of salmon lice on two salmon farms in the Broughton Archipelago, British Columbia
Martin Krkoˇsek1, 4,*, Andrew Bateman2, Stan Proboszcz3, Craig Orr3
1School of Aquatic and Fishery Science, University of Washington, Seattle, Washington 98105, USA
2Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, UK
3Watershed Watch Salmon Society, Coquitlam, British Columbia V3K 3B7, Canada
4Present address: Department of Zoology, University of Otago, Dunedin 9016, New Zealand
ABSTRACT: Outbreaks of parasitic salmon lice Lepeoptheirus salmonis in sea-cage salmon farming regions of coastal seas have challenged the productivity of salmon farming industries and the conservation of wild salmon. We used a simple mathematical model to evaluate the population ecology of louse outbreaks, parasiticide treatment, and louse population decline for 2 farms in the Broughton Archipelago region of British Columbia, Canada. Results suggest that exponential population growth of lice within a farm, rather than sustained louse immigration from wild sources, drive outbreaks on farms. Model analysis indicates that louse infection pressure from farms to wild juvenile salmon may be minimized by parasiticide application 2 to 3 mo preceding the juvenile salmon outmigration. The observed timing of parasiticide use and population decline of lice on farms is consistent with reported declines of lice on wild juvenile salmon. If parasiticides do not have adverse environmental effects and lice do not evolve resistance, optimized parasiticide use on salmon farms may help reduce the spread of lice to wild salmon populations.
KEY WORDS: Salmon • Sea lice • Aquaculture • Parasite • Outbreak • Eradication
14 DECEMBER 2007 VOL 318 SCIENCE www.sciencemag.org
Declining Wild Salmon Populations in Relation to Parasites from Farm Salmon
Martin Krkošek,1,2† Jennifer S. Ford,3 Alexandra Morton,4 Subhash Lele,1Ransom A. Myers,3* Mark A. Lewis1,2
Rather than benefiting wild fish, industrial aquaculture may contribute to declines in ocean fisheries and ecosystems. Farm salmon are commonly infected with salmon lice (Lepeophtheirus salmonis), which are native ectoparasitic copepods. We show that recurrent louse infestations of wild juvenile pink salmon (Oncorhynchus gorbuscha), all associated with salmon farms, have depressed wild pink salmon populations and placed them on a trajectory toward rapid local extinction. The louse-induced mortality of pink salmon is commonly over 80% and exceeds previous fishing mortality. If outbreaks continue, then local extinction is certain, and a 99% collapse in pink salmon population abundance is expected in four salmon generations. These results suggest that salmon farms can cause parasite outbreaks that erode the capacity of a coastal ecosystem to support wild salmon populations.
Declining Wild Salmon Populations in Relation to Parasites from Farm Salmon
Martin Krkošek,1,2† Jennifer S. Ford,3 Alexandra Morton,4 Subhash Lele,1Ransom A. Myers,3* Mark A. Lewis1,2
Rather than benefiting wild fish, industrial aquaculture may contribute to declines in ocean fisheries and ecosystems. Farm salmon are commonly infected with salmon lice (Lepeophtheirus salmonis), which are native ectoparasitic copepods. We show that recurrent louse infestations of wild juvenile pink salmon (Oncorhynchus gorbuscha), all associated with salmon farms, have depressed wild pink salmon populations and placed them on a trajectory toward rapid local extinction. The louse-induced mortality of pink salmon is commonly over 80% and exceeds previous fishing mortality. If outbreaks continue, then local extinction is certain, and a 99% collapse in pink salmon population abundance is expected in four salmon generations. These results suggest that salmon farms can cause parasite outbreaks that erode the capacity of a coastal ecosystem to support wild salmon populations.
© The Ecological Society of America
ecology and policy
Martin Krkos˘ek
The spread of sea lice (Lepeophtheirus salmonis) from salmon farms probably contributes to declines of some native Pacific salmon populations. Migration normally protects juvenile wild Pacific salmon from the marine ectoparasite in coastal waters by separating juvenile salmon from infected wild adults that are located offshore. Farmed salmon populations dwarf natural coastal host populations, particularly in winter, leading to biomagnification of louse populations. By spring, there may be large numbers of lice on farmed salmon, and this is associated with recurrent parasite infestations of wild juvenile salmon and depressed wild salmon stocks. Abiotic (eg temperature and salinity), biotic (eg predator abundance and food availability), and management (eg periodically emptying farms and applying chemical parasiticides) factors are thought to mediate the louse threat, but none have been well studied. Policy is needed that protects undeveloped juvenile salmon habitats and that supports long-term study of salmon ecosystems, to evaluate the sustainability of wild and farmed salmon.
Front Ecol Environ 2009; doi:10.1890/080097
ecology and policy
Martin Krkos˘ek
The spread of sea lice (Lepeophtheirus salmonis) from salmon farms probably contributes to declines of some native Pacific salmon populations. Migration normally protects juvenile wild Pacific salmon from the marine ectoparasite in coastal waters by separating juvenile salmon from infected wild adults that are located offshore. Farmed salmon populations dwarf natural coastal host populations, particularly in winter, leading to biomagnification of louse populations. By spring, there may be large numbers of lice on farmed salmon, and this is associated with recurrent parasite infestations of wild juvenile salmon and depressed wild salmon stocks. Abiotic (eg temperature and salinity), biotic (eg predator abundance and food availability), and management (eg periodically emptying farms and applying chemical parasiticides) factors are thought to mediate the louse threat, but none have been well studied. Policy is needed that protects undeveloped juvenile salmon habitats and that supports long-term study of salmon ecosystems, to evaluate the sustainability of wild and farmed salmon.
Front Ecol Environ 2009; doi:10.1890/080097
Reviews in Fisheries Science, 14:1–11, 2006
Copyright © Taylor & Francis Inc.
ISSN: 1064-1262 print
DOI: 10.1080/10641260500433531
Fish Farms and Sea Lice Infestations of Wild Juvenile Salmon in the Broughton Archipelago—A Rebuttal to Brooks (2005)
MARTIN KRKOˇSEK,1,2,3 MARK A. LEWIS,1,2
JOHN P. VOLPE,3 AND ALEXANDRA MORTON4
1Center for Mathematical Biology, Department of Mathematical and Statistical Sciences, University of Alberta, Edmonton, Alberta, Canada
2Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
3School of Environmental Studies, University of Victoria, Victoria, British Columbia, Canada
4Raincoast Research Society, Simoom Sound, British Columbia, Canada
Contrary to several recent studies, a review (Brooks, 2005) of sea lice (Lepeophtheirus salmonis) interactions between wild and farm salmon in the Broughton Archipelago, British Columbia, Canada, concluded that there is little potential for sea lice transmission from farm to wild salmon. In this rebuttal, we show that this conclusion was based on a flawed interpretation of how salinity affects louse development, a misunderstanding of how the timing of salinity changes corresponds to the timing of the juvenile salmon migration, models of larval dispersion that overestimate the transport of louse larvae, and a selective and misleading assessment of the literature. We analyze and extend the current models of larval dispersion and demonstrate the (perhaps counter-intuitive) result that sustained high abundances of infectious larvae should be expected near liceinfested salmon farms. We also highlight important studies overlooked in Brooks (2005) and clarify some misinterpretations. Counter to the conclusions in Brooks (2005), the modeling and empirical work to date on sea lice interactions between wild and farm salmon are consistent and point to a strong association between salmon farming and recurrent infestations of wild juvenile salmon in the Broughton Archipelago.
Keywords sea lice, aquaculture, salmon, parasite, dispersion, transmission dynamics, reservoir host, emerging disease
Copyright © Taylor & Francis Inc.
ISSN: 1064-1262 print
DOI: 10.1080/10641260500433531
Fish Farms and Sea Lice Infestations of Wild Juvenile Salmon in the Broughton Archipelago—A Rebuttal to Brooks (2005)
MARTIN KRKOˇSEK,1,2,3 MARK A. LEWIS,1,2
JOHN P. VOLPE,3 AND ALEXANDRA MORTON4
1Center for Mathematical Biology, Department of Mathematical and Statistical Sciences, University of Alberta, Edmonton, Alberta, Canada
2Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada
3School of Environmental Studies, University of Victoria, Victoria, British Columbia, Canada
4Raincoast Research Society, Simoom Sound, British Columbia, Canada
Contrary to several recent studies, a review (Brooks, 2005) of sea lice (Lepeophtheirus salmonis) interactions between wild and farm salmon in the Broughton Archipelago, British Columbia, Canada, concluded that there is little potential for sea lice transmission from farm to wild salmon. In this rebuttal, we show that this conclusion was based on a flawed interpretation of how salinity affects louse development, a misunderstanding of how the timing of salinity changes corresponds to the timing of the juvenile salmon migration, models of larval dispersion that overestimate the transport of louse larvae, and a selective and misleading assessment of the literature. We analyze and extend the current models of larval dispersion and demonstrate the (perhaps counter-intuitive) result that sustained high abundances of infectious larvae should be expected near liceinfested salmon farms. We also highlight important studies overlooked in Brooks (2005) and clarify some misinterpretations. Counter to the conclusions in Brooks (2005), the modeling and empirical work to date on sea lice interactions between wild and farm salmon are consistent and point to a strong association between salmon farming and recurrent infestations of wild juvenile salmon in the Broughton Archipelago.
Keywords sea lice, aquaculture, salmon, parasite, dispersion, transmission dynamics, reservoir host, emerging disease
PLoS ONE | www.plosone.org 1 February 2011 | Volume 6 | Issue 2 | e16851
Sea Louse Infection of Juvenile Sockeye Salmon in Relation to Marine Salmon Farms on Canada’s West Coast
Michael H. H. Price1,2*, Stan L. Proboszcz3, Rick D. Routledge4, Allen S. Gottesfeld5, Craig Orr3, John D. Reynolds6
1 Department of Biology, University of Victoria, Victoria, Canada,
2 Raincoast Conservation Foundation, Sidney, Canada,
3 Watershed Watch Salmon Society, Coquitlam, Canada,
4 Department of Statistics and Actuarial Science, Simon Fraser University, Burnaby, Canada,
5 Skeena Fisheries Commission, Hazelton, Canada,
6 Earth to Ocean Research Group, Department of Biology, Simon Fraser University, Burnaby, Canada
Abstract
Background: Pathogens are growing threats to wildlife. The rapid growth of marine salmon farms over the past two decades has increased host abundance for pathogenic sea lice in coastal waters, and wild juvenile salmon swimming past farms are frequently infected with lice. Here we report the first investigation of the potential role of salmon farms in transmitting sea lice to juvenile sockeye salmon (Oncorhynchus nerka). Methodology/Principal Findings: We used genetic analyses to determine the origin of sockeye from Canada’s two most important salmon rivers, the Fraser and Skeena; Fraser sockeye migrate through a region with salmon farms, and Skeena sockeye do not. We compared lice levels between Fraser and Skeena juvenile sockeye, and within the salmon farm region we compared lice levels on wild fish either before or after migration past farms. We matched the latter data on wild juveniles with sea lice data concurrently gathered on farms. Fraser River sockeye migrating through a region with salmon farms hosted an order of magnitude more sea lice than Skeena River populations, where there are no farms. Lice abundances on juvenile sockeye in the salmon farm region were substantially higher downstream of farms than upstream of farms for the two common species of lice: Caligus clemensi and Lepeophtheirus salmonis, and changes in their proportions between two years matched changes on the fish farms. Mixed-effects models show that position relative to salmon farms best explained C. clemensi abundance on sockeye, while migration year combined with position relative to salmon farms and temperature was one of two top models to explain L. salmonis abundance.
Conclusions/Significance: This is the first study to demonstrate a potential role of salmon farms in sea lice transmission to juvenile sockeye salmon during their critical early marine migration. Moreover, it demonstrates a major migration corridor past farms for sockeye that originated in the Fraser River, a complex of populations that are the subject of conservation concern.
Citation: Price MHH, Proboszcz SL, Routledge RD, Gottesfeld AS, Orr C, et al. (2011) Sea Louse Infection of Juvenile Sockeye Salmon in Relation to Marine Salmon Farms on Canada’s West Coast. PLoS ONE 6(2): e16851. doi:10.1371/journal.pone.0016851
Editor: Brock Fenton, University of Western Ontario, Canada
Received September 17, 2010; Accepted January 13, 2011; Published February 9, 2011
Copyright: 2011 Price et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funding: The work was funded by: The Coastal Alliance for Aquaculture Reform (www.farmedanddangerous.org), David and Lucile Packard Foundation (www.packard.org), Gordon and Betty Moore Foundation (www.moore.org), Patrick Hodgson Family Foundation, Ritchie Foundation, Sandler Family Foundation, SOS Marine Conservation Foundation (www.saveoursalmon.ca), Tom Buell Endowment Fund, a Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery Grants to RD Routledge and JD Reynolds (www.nserc-crsng.gc.ca), and an NSERC Industrial Postgraduate Scholarship to MHH Price. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing Interests: The authors have declared that no competing interests exist.
E-mail: pricem@uvic.ca
Sea Louse Infection of Juvenile Sockeye Salmon in Relation to Marine Salmon Farms on Canada’s West Coast
Michael H. H. Price1,2*, Stan L. Proboszcz3, Rick D. Routledge4, Allen S. Gottesfeld5, Craig Orr3, John D. Reynolds6
1 Department of Biology, University of Victoria, Victoria, Canada,
2 Raincoast Conservation Foundation, Sidney, Canada,
3 Watershed Watch Salmon Society, Coquitlam, Canada,
4 Department of Statistics and Actuarial Science, Simon Fraser University, Burnaby, Canada,
5 Skeena Fisheries Commission, Hazelton, Canada,
6 Earth to Ocean Research Group, Department of Biology, Simon Fraser University, Burnaby, Canada
Abstract
Background: Pathogens are growing threats to wildlife. The rapid growth of marine salmon farms over the past two decades has increased host abundance for pathogenic sea lice in coastal waters, and wild juvenile salmon swimming past farms are frequently infected with lice. Here we report the first investigation of the potential role of salmon farms in transmitting sea lice to juvenile sockeye salmon (Oncorhynchus nerka). Methodology/Principal Findings: We used genetic analyses to determine the origin of sockeye from Canada’s two most important salmon rivers, the Fraser and Skeena; Fraser sockeye migrate through a region with salmon farms, and Skeena sockeye do not. We compared lice levels between Fraser and Skeena juvenile sockeye, and within the salmon farm region we compared lice levels on wild fish either before or after migration past farms. We matched the latter data on wild juveniles with sea lice data concurrently gathered on farms. Fraser River sockeye migrating through a region with salmon farms hosted an order of magnitude more sea lice than Skeena River populations, where there are no farms. Lice abundances on juvenile sockeye in the salmon farm region were substantially higher downstream of farms than upstream of farms for the two common species of lice: Caligus clemensi and Lepeophtheirus salmonis, and changes in their proportions between two years matched changes on the fish farms. Mixed-effects models show that position relative to salmon farms best explained C. clemensi abundance on sockeye, while migration year combined with position relative to salmon farms and temperature was one of two top models to explain L. salmonis abundance.
Conclusions/Significance: This is the first study to demonstrate a potential role of salmon farms in sea lice transmission to juvenile sockeye salmon during their critical early marine migration. Moreover, it demonstrates a major migration corridor past farms for sockeye that originated in the Fraser River, a complex of populations that are the subject of conservation concern.
Citation: Price MHH, Proboszcz SL, Routledge RD, Gottesfeld AS, Orr C, et al. (2011) Sea Louse Infection of Juvenile Sockeye Salmon in Relation to Marine Salmon Farms on Canada’s West Coast. PLoS ONE 6(2): e16851. doi:10.1371/journal.pone.0016851
Editor: Brock Fenton, University of Western Ontario, Canada
Received September 17, 2010; Accepted January 13, 2011; Published February 9, 2011
Copyright: 2011 Price et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funding: The work was funded by: The Coastal Alliance for Aquaculture Reform (www.farmedanddangerous.org), David and Lucile Packard Foundation (www.packard.org), Gordon and Betty Moore Foundation (www.moore.org), Patrick Hodgson Family Foundation, Ritchie Foundation, Sandler Family Foundation, SOS Marine Conservation Foundation (www.saveoursalmon.ca), Tom Buell Endowment Fund, a Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery Grants to RD Routledge and JD Reynolds (www.nserc-crsng.gc.ca), and an NSERC Industrial Postgraduate Scholarship to MHH Price. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing Interests: The authors have declared that no competing interests exist.
E-mail: pricem@uvic.ca
Journal of Fish Diseases 2013 doi:10.1111/jfd.12061
Review
Salmon lice – impact on wild salmonids and salmon aquaculture
O Torrissen1,2, S Jones3, F Asche4, A Guttormsen5, O T Skilbrei6, F Nilsen7, T E Horsberg 8 and D Jackson9
1 Institute of Marine Research, Bergen, Norway
2 Faculty of Biosciences and Aquaculture, University of Nordland, Bodø, Norway
3 Pacific Biological Station, Fisheries and Oceans Canada, Nanaimo, British Columbia, Canada
4 Department of Industrial Economics, University of Stavanger, Stavanger, Norway
5 UMB School of Economics and Business, Norwegian University of Life Sciences, A ° s, Norway
6 Department of Population Genetics and Ecology, Institute of Marine Research, Bergen, Norway
7 Department of Biology, Sea Lice Research Centre, University of Bergen, Bergen, Norway
8 Department of Pharmacology and Toxicology, Norwegian School of Veterinary Science, Oslo, Norway
9 Marine Institute, Galway, Ireland
Abstract
Salmon lice, Lepeophtheirus salmonis, are naturally occurring parasites of salmon in sea water. Intensive salmon farming provides better conditions for parasite growth and transmission compared with natural conditions, creating problems for both the salmon farming industry and, under certain conditions, wild salmonids. Salmon lice originating from farms negatively impact wild stocks of salmonids, although the extent of the impact is a matter of debate. Estimates from Ireland and Norway indicate an odds ratio of 1.1:1-1.2:1 for sea lice treated Atlantic salmon smolt to survive sea migration compared to untreated smolts. This is considered to have a moderate population regulatory effect. The development of resistance against drugs most commonly used to treat salmon lice is a serious concern for both wild and farmed fish. Several large initiatives have been taken to encourage the development of new strategies, such as vaccines and novel drugs, for the treatment or removal of salmon lice from farmed fish. The newly sequenced salmon louse genome will be an important tool in this work. The use of cleaner fish has emerged as a robust method for controlling salmon lice, and aquaculture production of wrasse is important towards this aim. Salmon lice have large economic consequences for the salmon industry, both as direct costs for the prevention and treatment, but also indirectly through negative public opinion. Keywords: aquaculture, Atlantic salmon, Lepeophtheirus salmonis, management, Pacific salmon, socio-economic impact.
Review
Salmon lice – impact on wild salmonids and salmon aquaculture
O Torrissen1,2, S Jones3, F Asche4, A Guttormsen5, O T Skilbrei6, F Nilsen7, T E Horsberg 8 and D Jackson9
1 Institute of Marine Research, Bergen, Norway
2 Faculty of Biosciences and Aquaculture, University of Nordland, Bodø, Norway
3 Pacific Biological Station, Fisheries and Oceans Canada, Nanaimo, British Columbia, Canada
4 Department of Industrial Economics, University of Stavanger, Stavanger, Norway
5 UMB School of Economics and Business, Norwegian University of Life Sciences, A ° s, Norway
6 Department of Population Genetics and Ecology, Institute of Marine Research, Bergen, Norway
7 Department of Biology, Sea Lice Research Centre, University of Bergen, Bergen, Norway
8 Department of Pharmacology and Toxicology, Norwegian School of Veterinary Science, Oslo, Norway
9 Marine Institute, Galway, Ireland
Abstract
Salmon lice, Lepeophtheirus salmonis, are naturally occurring parasites of salmon in sea water. Intensive salmon farming provides better conditions for parasite growth and transmission compared with natural conditions, creating problems for both the salmon farming industry and, under certain conditions, wild salmonids. Salmon lice originating from farms negatively impact wild stocks of salmonids, although the extent of the impact is a matter of debate. Estimates from Ireland and Norway indicate an odds ratio of 1.1:1-1.2:1 for sea lice treated Atlantic salmon smolt to survive sea migration compared to untreated smolts. This is considered to have a moderate population regulatory effect. The development of resistance against drugs most commonly used to treat salmon lice is a serious concern for both wild and farmed fish. Several large initiatives have been taken to encourage the development of new strategies, such as vaccines and novel drugs, for the treatment or removal of salmon lice from farmed fish. The newly sequenced salmon louse genome will be an important tool in this work. The use of cleaner fish has emerged as a robust method for controlling salmon lice, and aquaculture production of wrasse is important towards this aim. Salmon lice have large economic consequences for the salmon industry, both as direct costs for the prevention and treatment, but also indirectly through negative public opinion. Keywords: aquaculture, Atlantic salmon, Lepeophtheirus salmonis, management, Pacific salmon, socio-economic impact.
Journal of Fish Diseases 2009, 32, 45–57 doi:10.1111/j.1365-2761.2008.01003.x
Sea lice, Lepeophtheirus salmonis, transfer between wild sympatric adult and juvenile salmon on the north coast of British Columbia, Canada
A S Gottesfeld1, B Proctor2, L D Rolston2 and C Carr-Harris1
1 Skeena Fisheries Commission, Hazelton, BC, Canada
2 Oona River Resources Association, Prince Rupert, BC, Canada
Abstract
We examine sea lice, Lepeophtheirus salmonis, on juvenile and adult salmon from the north coast of British Columbia between 2004 and 2006 in an area that does not at present contain salmon farms. There is a pronounced zonation in the abundance of L. salmonis on juvenile pink salmon, Oncorhynchus gorbuscha, in the Skeena and Nass estuaries. Abundances in the proximal and distal zones of these estuaries are 0.01 and 0.05 respectively. The outer zones serve as feeding and staging areas for the pink salmon smolts. Returning Chinook, Oncorhynchus tshawytscha, and coho salmon, Oncorhynchus kisutch, concentrate in these areas. We collected data in 2006 to examine whether L. salmonis on returning adult salmon are an important source of the sea lice that appear on juvenile pink salmon. Nearly all (99%) of the sea lice on returning Chinook and over 80% on coho salmon were L. salmonis. Most of the L. salmonis were motile stages including many ovigerous females. There was a sharp increase in the abundance of sea lice on juvenile pink salmon smolts between May and July 2006 near the sites of adult captures. As there are no salmon farms on the north coast, few sticklebacks, Gasterosteus aculeatus, and very few resident salmonids until later in the summer, it seems that the most important reservoir of L. salmonis under natural conditions is returning adult salmon. This natural source of sea lice results in levels of abundance that are one or two orders of magnitude lower than those observed on juvenile pink salmon in areas with salmon farms such as the Broughton Archipelago.
Keywords: Chinook salmon, Lepeophtheirus salmonis, pink salmon, sea lice, sea lice epizootiology, wild salmon.
Sea lice, Lepeophtheirus salmonis, transfer between wild sympatric adult and juvenile salmon on the north coast of British Columbia, Canada
A S Gottesfeld1, B Proctor2, L D Rolston2 and C Carr-Harris1
1 Skeena Fisheries Commission, Hazelton, BC, Canada
2 Oona River Resources Association, Prince Rupert, BC, Canada
Abstract
We examine sea lice, Lepeophtheirus salmonis, on juvenile and adult salmon from the north coast of British Columbia between 2004 and 2006 in an area that does not at present contain salmon farms. There is a pronounced zonation in the abundance of L. salmonis on juvenile pink salmon, Oncorhynchus gorbuscha, in the Skeena and Nass estuaries. Abundances in the proximal and distal zones of these estuaries are 0.01 and 0.05 respectively. The outer zones serve as feeding and staging areas for the pink salmon smolts. Returning Chinook, Oncorhynchus tshawytscha, and coho salmon, Oncorhynchus kisutch, concentrate in these areas. We collected data in 2006 to examine whether L. salmonis on returning adult salmon are an important source of the sea lice that appear on juvenile pink salmon. Nearly all (99%) of the sea lice on returning Chinook and over 80% on coho salmon were L. salmonis. Most of the L. salmonis were motile stages including many ovigerous females. There was a sharp increase in the abundance of sea lice on juvenile pink salmon smolts between May and July 2006 near the sites of adult captures. As there are no salmon farms on the north coast, few sticklebacks, Gasterosteus aculeatus, and very few resident salmonids until later in the summer, it seems that the most important reservoir of L. salmonis under natural conditions is returning adult salmon. This natural source of sea lice results in levels of abundance that are one or two orders of magnitude lower than those observed on juvenile pink salmon in areas with salmon farms such as the Broughton Archipelago.
Keywords: Chinook salmon, Lepeophtheirus salmonis, pink salmon, sea lice, sea lice epizootiology, wild salmon.
The Relationship Between Sea Lice Infestation, Sea Lice Production And
Sea Trout Survival In Ireland, 1992-2001.
P. G. Gargan*, Central Fisheries Board, Mobhi Road, Glasnevin Dublin 9, Ireland.
P. Tully, Zoology Department, Trinity College, Dublin 2, Ireland.
W. R. Poole, Marine Institute, Newport, Co. Mayo, Ireland.
*Corresponding Author: E-mail; paddy.gargan@cfb.ie
ABSTRACT
The relationship between sea lice infestation on sea trout with distance to salmon aquaculture sites for a broad geographic range of Irish rivers was examined over a ten year period. Highest mean levels of total lice and juvenile (chalimus stages) lice were recorded at sites less than 20 km from farms. The mean total lice infestation was lower at sites less than 30 km from farms and beyond 30 km, very low mean total lice levels were recorded. Chalimus lice stages dominated the sea lice population structure at distances <20 and <30 km. At distances <60 and <100 km chalimus and post chalimus stages are equally represented and at sites >100km post chalimus stages predominate. A model was fitted to pooled 10 year data time series for sea lice infestation and distance from marine salmon farms to indicate an overall relationship that could be used to support management actions. The average abundance of lice per fish expected very close to farms (1km) was 50.6. Regression of log-transformed data for individual years showed significant relationships in all years except 1994 and 1999 although substantial variation existed in the data particularly close to farms. Infestations at distances greater than 25 km, never reached over 32 lice per fish and were usually much lower. At distances less than 25 km the full range in infestation occurred. Sea trout have been shown to experience physiological problems and osmoregulatory imbalance at lice levels of approximately 0.7 lice larva.g-1fish weight. The overall mean size of trout in the present study carrying lice was 79g giving an indicative stress level of sea lice infestation of 55 lice/fish. Twenty nine percent of the infested trout had lice levels above this indicative stress level. For fish sampled in bays without farms, 3.4% of the infested trout were above this indicative stress level while for fish captured in bays with farms this level rose to 30.8%. There was a relationship between the proportion of fish in each sample above 55 lice per fish and distance from salmon farms. There was a significant negative relationship between sea trout marine survival and the level of lice infestation on sea trout in four bays in the mid-West. A linear model of the relationship between the total number of ovigerous lice produced in two bays between March to mid-May and the average number of sea lice infesting sea trout in nearby rivers showed a significant positive relationship between lice reproductive potential and infestation of trout. The relationships shown in the present study indicate that sea lice from marine salmon farms were a major contributory factor in the sea trout stock collapses observed in aquaculture areas in western Ireland. If recovery of depleted sea trout stocks is to be achieved in this area it is critical to ensure that ovigerous sea lice levels are maintained at near zero levels on marine salmon farms over the spring period prior to and during sea trout smolt migration. This must be achieved on a consistent annual basis for a successful sea trout recovery.
Sea Trout Survival In Ireland, 1992-2001.
P. G. Gargan*, Central Fisheries Board, Mobhi Road, Glasnevin Dublin 9, Ireland.
P. Tully, Zoology Department, Trinity College, Dublin 2, Ireland.
W. R. Poole, Marine Institute, Newport, Co. Mayo, Ireland.
*Corresponding Author: E-mail; paddy.gargan@cfb.ie
ABSTRACT
The relationship between sea lice infestation on sea trout with distance to salmon aquaculture sites for a broad geographic range of Irish rivers was examined over a ten year period. Highest mean levels of total lice and juvenile (chalimus stages) lice were recorded at sites less than 20 km from farms. The mean total lice infestation was lower at sites less than 30 km from farms and beyond 30 km, very low mean total lice levels were recorded. Chalimus lice stages dominated the sea lice population structure at distances <20 and <30 km. At distances <60 and <100 km chalimus and post chalimus stages are equally represented and at sites >100km post chalimus stages predominate. A model was fitted to pooled 10 year data time series for sea lice infestation and distance from marine salmon farms to indicate an overall relationship that could be used to support management actions. The average abundance of lice per fish expected very close to farms (1km) was 50.6. Regression of log-transformed data for individual years showed significant relationships in all years except 1994 and 1999 although substantial variation existed in the data particularly close to farms. Infestations at distances greater than 25 km, never reached over 32 lice per fish and were usually much lower. At distances less than 25 km the full range in infestation occurred. Sea trout have been shown to experience physiological problems and osmoregulatory imbalance at lice levels of approximately 0.7 lice larva.g-1fish weight. The overall mean size of trout in the present study carrying lice was 79g giving an indicative stress level of sea lice infestation of 55 lice/fish. Twenty nine percent of the infested trout had lice levels above this indicative stress level. For fish sampled in bays without farms, 3.4% of the infested trout were above this indicative stress level while for fish captured in bays with farms this level rose to 30.8%. There was a relationship between the proportion of fish in each sample above 55 lice per fish and distance from salmon farms. There was a significant negative relationship between sea trout marine survival and the level of lice infestation on sea trout in four bays in the mid-West. A linear model of the relationship between the total number of ovigerous lice produced in two bays between March to mid-May and the average number of sea lice infesting sea trout in nearby rivers showed a significant positive relationship between lice reproductive potential and infestation of trout. The relationships shown in the present study indicate that sea lice from marine salmon farms were a major contributory factor in the sea trout stock collapses observed in aquaculture areas in western Ireland. If recovery of depleted sea trout stocks is to be achieved in this area it is critical to ensure that ovigerous sea lice levels are maintained at near zero levels on marine salmon farms over the spring period prior to and during sea trout smolt migration. This must be achieved on a consistent annual basis for a successful sea trout recovery.
Proc. R. Soc. B
doi:10.1098/rspb.2009.0771
Published online
How sea lice from salmon farms may cause wild salmonid declines in Europe and North America and be a threat to fishes elsewhere
Mark J. Costello*
Leigh Marine Laboratory, University of Auckland, PO Box 347, Warkworth, New Zealand
Fishes farmed in sea pens may become infested by parasites from wild fishes and in turn become point sources for parasites. Sea lice, copepods of the family Caligidae, are the best-studied example of this risk. Sea lice are the most significant parasitic pathogen in salmon farming in Europe and the Americas, are estimated to cost the world industry E300 million a year and may also be pathogenic to wild fishes under natural conditions. Epizootics, characteristically dominated by juvenile (copepodite and chalimus) stages, have repeatedly occurred on juvenile wild salmonids in areas where farms have sea lice infestations, but have not been recorded elsewhere. This paper synthesizes the literature, including modelling studies, to provide an understanding of how one species, the salmon louse, Lepeophtheirus salmonis, can infest wild salmonids from farm sources. Three-dimensional hydrographic models predicted the distribution of the planktonic salmon lice larvae best when they accounted for wind-driven surface currents and larval behaviour. Caligus species can also cause problems on farms and transfer from farms to wild fishes, and this genus is cosmopolitan. Sea lice thus threaten finfish farming worldwide, but with the possible exception of L. salmonis, their host relationships and transmission adaptations are unknown. The increasing evidence that lice from farms can be a significant cause of mortality on nearby wild fish populations provides an additional challenge to controlling lice on the farms and also raises conservation, economic and political issues about how to balance aquaculture and fisheries resource management.
Keywords: Caligus; Lepeophtheirus; trout; epizootics; aquaculture; ectoparasites
doi:10.1098/rspb.2009.0771
Published online
How sea lice from salmon farms may cause wild salmonid declines in Europe and North America and be a threat to fishes elsewhere
Mark J. Costello*
Leigh Marine Laboratory, University of Auckland, PO Box 347, Warkworth, New Zealand
Fishes farmed in sea pens may become infested by parasites from wild fishes and in turn become point sources for parasites. Sea lice, copepods of the family Caligidae, are the best-studied example of this risk. Sea lice are the most significant parasitic pathogen in salmon farming in Europe and the Americas, are estimated to cost the world industry E300 million a year and may also be pathogenic to wild fishes under natural conditions. Epizootics, characteristically dominated by juvenile (copepodite and chalimus) stages, have repeatedly occurred on juvenile wild salmonids in areas where farms have sea lice infestations, but have not been recorded elsewhere. This paper synthesizes the literature, including modelling studies, to provide an understanding of how one species, the salmon louse, Lepeophtheirus salmonis, can infest wild salmonids from farm sources. Three-dimensional hydrographic models predicted the distribution of the planktonic salmon lice larvae best when they accounted for wind-driven surface currents and larval behaviour. Caligus species can also cause problems on farms and transfer from farms to wild fishes, and this genus is cosmopolitan. Sea lice thus threaten finfish farming worldwide, but with the possible exception of L. salmonis, their host relationships and transmission adaptations are unknown. The increasing evidence that lice from farms can be a significant cause of mortality on nearby wild fish populations provides an additional challenge to controlling lice on the farms and also raises conservation, economic and political issues about how to balance aquaculture and fisheries resource management.
Keywords: Caligus; Lepeophtheirus; trout; epizootics; aquaculture; ectoparasites
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