Fish Farm trouble in BC.
- Thread starter Chuck
- Start date
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bigdogeh
Well-Known Member
Please re-read the first line of AA's post 3 posts before yours.
Then please show me a direct study that says "wild Pacific salmon are not dying because of farmed fish"
Bones - many posters have ALREADY gave you those links. and there is a thing called "GOOGLE" (and Google scholar https://scholar.google.ca/ ) where you can find the hundreds of peer-reviewed and grey literature reports yourself - but only if you want to. If it is instead safer for you not to know and not to inform yourself - that is of course your prerogative. It is hard to have a debate with an uniformed person on what they consider their beliefs are. They seem to get quite defensive and stop reading any science that contradicts their beliefs. That doesn't mean the other posters on this forum don't read and appreciate the science, however.
It is also absurd and irresponsible to attempt to claim that simply because some chartmaker typed "Pacific" on the water on the West side of North America that somehow we are magically immune from many of the exact impacts in the Atlantic - the issue of inbreeding with local wild Atlantic stocks being the one I can think of that doesn't apply - as Dave pointed out.
It is also absurd and irresponsible to attempt to claim that simply because some chartmaker typed "Pacific" on the water on the West side of North America that somehow we are magically immune from many of the exact impacts in the Atlantic - the issue of inbreeding with local wild Atlantic stocks being the one I can think of that doesn't apply - as Dave pointed out.
fogged in
Well-Known Member
Dave and Bones
Do you recall my question asked many times to the Fish Farm supporters?
Last asked AGAIN just last Wednesday.
You and the others refuse to answer it.
You make like you are very well informed and should have no trouble answering this simple question which is so central to this debate.
I will ask it one more time....
Can you please give a simple answer without deflection?
Do Fish Farm Sea Lice and disease kill Wild Salmon?
Yes Fish Farms do kill wild salmon but no one can prove how many
or
No Fish Farm Sea Lice never have and never will kill any wild salmon
Can't answer your question as the only sea lice I have seen are the ones attached to pink fry in bottles filled with formalin, or the ones I have seen on the salmon I have caught or sampled. And, afaik, no measurable numbers of wild salmon have died from any disease attributed to contact with farmed fish.
Please correct me if I'm wrong.
Please correct me if I'm wrong.
fogged in
Well-Known Member
Thanks for the reply Dave
Is it safe to say, In your opinion, Fish Farm Sea Lice do not and have not killed any wild salmon???
Yes or no???
I think we have already been through this a few times already, dave. memory getting shorter w age?
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.
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ICES Journal of Marine Science, 59: 131–139. 2002
doi:10.1006/jmsc.2001.1143, available online at http://www.idealibrary.com on
Salmon lice, Lepeophtheirus salmonis (Krøyer), infestation in sympatric populations of Arctic char, Salvelinus alpinus (L.), and sea trout, Salmo trutta (L.), in areas near and distant from salmon farms
Pa°l Arne Bjørn and Bengt Finstad
Bjørn, P. A., and Finstad, B. 2002. Salmon lice, Lepeophtheirus salmonis (Krøyer), infestation in sympatric populations of Arctic char, Salvelinus alpinus (L.), and sea trout, Salmo trutta (L.), in areas near and distant from salmon farms. – ICES Journal of Marine Science, 59: 131–139.
The abundance of salmon lice was examined in two stocks of sympatric anadromous Arctic char and sea trout in sub-Arctic regions in northern Norway in June, July, and August 1992 and 1993. One stock feeds in a coastal area exposed to moderate salmon farming activity (exposed area), while the other feed in a region without salmon farms (unexposed area). The salmon lice infestation on both species differed significantly between the exposed and unexposed area as well as between years and also between weeks within the same year. We did not detect, however, any clear significant differences in salmon lice abundance between sympatric populations of Arctic char and sea trout, or between different size groups of the species. The 1992 and 1993 infestation pattern in the exposed area showed an epidemic tendency in both Arctic char and sea trout, characterised by a sudden increase in both prevalence and abundance of lice larvae in July 1992 (23.625.7 lice/fish) and August 1993 (19.920.8 lice/fish). We therefore suggest that salmon lice epidemics, previously only observed on sea trout, may also occur in populations of Arctic char, and that fish farming contributes to the elevated lice level in wild fish. The fish in the unexposed area were also infested, although at significantly lower levels than fish from the exposed area. The infestation peaked in August 1992 at 13.018.1 lice/fish and August 1993 at 3.94.5 lice/fish, suggested that lice originating on ascending wild Atlantic salmon, or lice larvae drifting from farming areas, may infest Arctic char and sea trout also in unexposed localities in Subarctic areas.
[1] 2002 International Council for the Exploration of the Sea
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Characteristics of the sea trout, Salmo trutta L., stocks from the Owengowla and Invermore Fisheries, Connemara, Western Ireland, and recent trends in marine survival.
Gargan, P. G., Roche, W. K., Forde, & G.P. Ferguson, A.
ABSTRACT
The Owengowla and Invermore sea trout fisheries, situated in Connemara, Western Ireland, have historically been important sea trout angling fisheries. Like other midwestern sea trout fisheries, both suffered a sea trout stock collapse in 1989. Upstream and downstream traps were installed on both fisheries and data on sea trout smolt and kelt runs, age and length frequency of migrants, and marine survival over the 1991 – 2003 period are presented. The trapping data indicates that substantial runs of sea trout smolts were derived from an extremely small spawning escapement of sea trout, implying that the freshwater trout stock contribute significantly to sea trout smolt runs in both systems. Exceptionally low sea trout finnock (0-sea winter) marine survival rates were recorded annually for the Owengowla fishery over a ten year period, with the exception of one year when prolonged whole-bay spring fallowing of marine salmon farms
Alexandra Morton1, Rick Routledge2, Amy McConnell3, and Martin Krkosˇek1,4*†
1Salmon Coast Field Station, Simoom Sound, BC, Canada
2Department of Statistics and Actuarial Science, Simon Fraser University, Burnaby, British Columbia, Canada
3Department of Biology, Simon Fraser University, Burnaby, British Columbia, Canada
4School of Aquatic and Fishery Sciences, University of Washington, Seattle, Washington, USA
*Corresponding Author: tel: +1 250 974 7177; fax: +1 206 685 7471; e-mail:mkrkosek@u.washington.edu.
†Present address: Department of Zoology, University of Otago, Dunedin, Otago, New Zealand.
Morton, A., Routledge, R., McConnell, A., and Krkosˇek, M. 2011. Sea lice dispersion and salmon survival in relation to salmon farm activity in the Broughton Archipelago. – ICES Journal of Marine Science, 68: 144–156.
Received 21 October 2009; accepted 3 August 2010; advance access publication 11 October 2010.
The risk of salmon lice (Lepeophtheirus salmonis) transmission to wild juvenile Pacific salmon has spurred management change to reduce lice on salmon farms. We studied the abundance of planktonic lice preceding the juvenile salmon outmigration as well as the abundance of lice on juvenile pink (Oncorhynchus gorbuscha) and chum (Oncorhynchus keta) salmon in two distinct migration routes, one containing only fallow farms and the other active farms that applied a parasiticide. Results indicate that fallowing reduces the abundance and flattens the spatial distribution of lice relative to that expected in areas without farms. Active farms remained the primary source of lice, but transmission was reduced 100-fold relative to previous epizootics in the study area. On the migration route containing active farms, [1]50% of the juvenile salmon showed evidence of louse damage to surface tissues and the estimated direct louse-induced mortality was ,10%, not including indirect effects of infection on predation risk or competition. The survival of the pink salmon cohort was not statistically different from a reference region without salmon farms. Although repeated use of a single parasiticide can lead to resistance, reducing louse transmission from farmed salmon may help conserve some wild Pacific salmon populations.
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Temporal and spatial patterns of sea lice levels on sea trout in western Scotland in relation to fish farm production cycles
S. J. Middlemas1,*, J. A. Raffell2, D. W. Hay1, M. Hatton-Ellis2 and J. D. Armstrong1
1Marine Scotland Science, Freshwater Laboratory, Faskally, Pitlochry PH16 5LB, UK
2Marine Scotland Science, Shieldaig Field Station, Shieldaig, Strathcarron IV54 8XJ, UK
*Author for correspondence (s.middlemas@marlab.ac.uk).
The relationship between aquaculture and infestations of sea lice on wild sea trout (Salmo trutta) populations is controversial. Although some authors have concluded that there is a link between aquaculture and lice burdens on wild fish, others have questioned this interpretation. Lice levels have been shown to be generally higher on Atlantic salmon farms during the second years of two-year production cycles. Here we investigate whether this pattern relates to lice burdens on wild fish across broad temporal and spatial axes. Within Loch Shieldaig across five successive farm cycles from 2000 to 2009, the percentage of sea trout with lice, and those above a critical level, were significantly higher in the second year of a two-year production cycle. These patterns were mirrored in 2002–2003 across the Scottish west coast. The results suggest a link between Atlantic salmon farms and sea lice burdens on sea trout in the west of Scotland.
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Transmission dynamics of parasitic sea lice from farm to wild salmon
Martin Krkosˇek1,2*, Mark A. Lewis1,2 and John P. Volpe2†
1Center for Mathematical Biology, Department of Mathematical and Statistical Sciences, and 2Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2E7
Marine salmon farming has been correlated with parasitic sea lice infestations and concurrent declines of wild salmonids. Here, we report a quantitative analysis of how a single salmon farm altered the natural transmission dynamics of sea lice to juvenile Pacific salmon. We studied infections of sea lice (Lepeophtheirus salmonis and Caligus clemensi ) on juvenile pink salmon (Oncorhynchus gorbuscha) and chum salmon (Oncorhynchus keta) as they passed an isolated salmon farm during their seaward migration down two long and narrow corridors. Our calculations suggest the infection pressure imposed by the farm was four orders of magnitude greater than ambient levels, resulting in a maximum infection pressure near the farmthat was 73 times greater than ambient levels and exceeded ambient levels for 30 km along the two wild salmon migration corridors. The farm-produced cohort of lice parasitizing the wild juvenile hosts reached reproductive maturity and produced a second generation of lice that re-infected the juvenile salmon. This raises the infection pressure from the farm by an additional order of magnitude, with a composite infection pressure that exceeds ambient levels for 75 km of the two migration routes. Amplified sea lice infestations due to salmon farms are a potential limiting factor to wild salmonid conservation.
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Critical thresholds in sea lice epidemics: evidence, sensitivity and subcritical estimation
L. Neil Frazer1,*, Alexandra Morton2 and Martin Krkosˇek3
1Department of Geology and Geophysics, School of Ocean and Earth Science and Technology, University of Hawaii at Manoa, Honolulu, HI 96822, USA
2Salmon Coast Field Station, Simoom Sound, British Columbia, Canada V0P 1S0
3Department of Zoology, University of Otago, Dunedin, New Zealand
Host density thresholds are a fundamental component of the population dynamics of pathogens, but empirical evidence and estimates are lacking. We studied host density thresholds in the dynamics of ectoparasitic sea lice (Lepeophtheirus salmonis) on salmon farms. Empirical examples include a 1994 epidemic in Atlantic Canada and a 2001 epidemic in Pacific Canada. A mathematical model suggests dynamics of lice are governed by a stable endemic equilibrium until the critical host density threshold drops owing to environmental change, or is exceeded by stocking, causing epidemics that require rapid harvest or treatment. Sensitivity analysis of the critical threshold suggests variation in dependence on biotic parameters and high sensitivity to temperature and salinity. We provide a method for estimating the critical threshold from parasite abundances at subcritical host densities and estimate the critical threshold and transmission coefficient for the two epidemics. Host density thresholds may be a fundamental component of disease dynamics in coastal seas where salmon farming occurs.
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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 and invertebrates 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.
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1Salmon Coast Field Station, Simoom Sound, BC, Canada
2Department of Statistics and Actuarial Science, Simon Fraser University, Burnaby, British Columbia, Canada
3Department of Biology, Simon Fraser University, Burnaby, British Columbia, Canada
4School of Aquatic and Fishery Sciences, University of Washington, Seattle, Washington, USA
*Corresponding Author: tel: +1 250 974 7177; fax: +1 206 685 7471; e-mail:mkrkosek@u.washington.edu.
†Present address: Department of Zoology, University of Otago, Dunedin, Otago, New Zealand.
Morton, A., Routledge, R., McConnell, A., and Krkosˇek, M. 2011. Sea lice dispersion and salmon survival in relation to salmon farm activity in the Broughton Archipelago. – ICES Journal of Marine Science, 68: 144–156.
Received 21 October 2009; accepted 3 August 2010; advance access publication 11 October 2010.
The risk of salmon lice (Lepeophtheirus salmonis) transmission to wild juvenile Pacific salmon has spurred management change to reduce lice on salmon farms. We studied the abundance of planktonic lice preceding the juvenile salmon outmigration as well as the abundance of lice on juvenile pink (Oncorhynchus gorbuscha) and chum (Oncorhynchus keta) salmon in two distinct migration routes, one containing only fallow farms and the other active farms that applied a parasiticide. Results indicate that fallowing reduces the abundance and flattens the spatial distribution of lice relative to that expected in areas without farms. Active farms remained the primary source of lice, but transmission was reduced 100-fold relative to previous epizootics in the study area. On the migration route containing active farms, [1]50% of the juvenile salmon showed evidence of louse damage to surface tissues and the estimated direct louse-induced mortality was ,10%, not including indirect effects of infection on predation risk or competition. The survival of the pink salmon cohort was not statistically different from a reference region without salmon farms. Although repeated use of a single parasiticide can lead to resistance, reducing louse transmission from farmed salmon may help conserve some wild Pacific salmon populations.
-----------------------------------------------------------------------------------------------------------------------------------------------------
Temporal and spatial patterns of sea lice levels on sea trout in western Scotland in relation to fish farm production cycles
S. J. Middlemas1,*, J. A. Raffell2, D. W. Hay1, M. Hatton-Ellis2 and J. D. Armstrong1
1Marine Scotland Science, Freshwater Laboratory, Faskally, Pitlochry PH16 5LB, UK
2Marine Scotland Science, Shieldaig Field Station, Shieldaig, Strathcarron IV54 8XJ, UK
*Author for correspondence (s.middlemas@marlab.ac.uk).
The relationship between aquaculture and infestations of sea lice on wild sea trout (Salmo trutta) populations is controversial. Although some authors have concluded that there is a link between aquaculture and lice burdens on wild fish, others have questioned this interpretation. Lice levels have been shown to be generally higher on Atlantic salmon farms during the second years of two-year production cycles. Here we investigate whether this pattern relates to lice burdens on wild fish across broad temporal and spatial axes. Within Loch Shieldaig across five successive farm cycles from 2000 to 2009, the percentage of sea trout with lice, and those above a critical level, were significantly higher in the second year of a two-year production cycle. These patterns were mirrored in 2002–2003 across the Scottish west coast. The results suggest a link between Atlantic salmon farms and sea lice burdens on sea trout in the west of Scotland.
------------------------------------------------------------------------------------------------------------------------------------------------------
Transmission dynamics of parasitic sea lice from farm to wild salmon
Martin Krkosˇek1,2*, Mark A. Lewis1,2 and John P. Volpe2†
1Center for Mathematical Biology, Department of Mathematical and Statistical Sciences, and 2Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2E7
Marine salmon farming has been correlated with parasitic sea lice infestations and concurrent declines of wild salmonids. Here, we report a quantitative analysis of how a single salmon farm altered the natural transmission dynamics of sea lice to juvenile Pacific salmon. We studied infections of sea lice (Lepeophtheirus salmonis and Caligus clemensi ) on juvenile pink salmon (Oncorhynchus gorbuscha) and chum salmon (Oncorhynchus keta) as they passed an isolated salmon farm during their seaward migration down two long and narrow corridors. Our calculations suggest the infection pressure imposed by the farm was four orders of magnitude greater than ambient levels, resulting in a maximum infection pressure near the farmthat was 73 times greater than ambient levels and exceeded ambient levels for 30 km along the two wild salmon migration corridors. The farm-produced cohort of lice parasitizing the wild juvenile hosts reached reproductive maturity and produced a second generation of lice that re-infected the juvenile salmon. This raises the infection pressure from the farm by an additional order of magnitude, with a composite infection pressure that exceeds ambient levels for 75 km of the two migration routes. Amplified sea lice infestations due to salmon farms are a potential limiting factor to wild salmonid conservation.
------------------------------------------------------------------------------------------------------------------------------------------------------
Critical thresholds in sea lice epidemics: evidence, sensitivity and subcritical estimation
L. Neil Frazer1,*, Alexandra Morton2 and Martin Krkosˇek3
1Department of Geology and Geophysics, School of Ocean and Earth Science and Technology, University of Hawaii at Manoa, Honolulu, HI 96822, USA
2Salmon Coast Field Station, Simoom Sound, British Columbia, Canada V0P 1S0
3Department of Zoology, University of Otago, Dunedin, New Zealand
Host density thresholds are a fundamental component of the population dynamics of pathogens, but empirical evidence and estimates are lacking. We studied host density thresholds in the dynamics of ectoparasitic sea lice (Lepeophtheirus salmonis) on salmon farms. Empirical examples include a 1994 epidemic in Atlantic Canada and a 2001 epidemic in Pacific Canada. A mathematical model suggests dynamics of lice are governed by a stable endemic equilibrium until the critical host density threshold drops owing to environmental change, or is exceeded by stocking, causing epidemics that require rapid harvest or treatment. Sensitivity analysis of the critical threshold suggests variation in dependence on biotic parameters and high sensitivity to temperature and salinity. We provide a method for estimating the critical threshold from parasite abundances at subcritical host densities and estimate the critical threshold and transmission coefficient for the two epidemics. Host density thresholds may be a fundamental component of disease dynamics in coastal seas where salmon farming occurs.
------------------------------------------------------------------------------------------------------------------------------------------------
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 and invertebrates 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.
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Effects of parasites from salmon farms on productivity of wild salmon
Martin Krkošeka,b,1, Brendan M. Connorsb,c, Alexandra Mortonb,d, Mark A. Lewise, Lawrence M. Dillc, and Ray Hilbornf
aDepartment of Zoology, University of Otago, Dunedin, New Zealand, 9016;
bSalmon Coast Field Station, Simoom Sound, BC, Canada V0P 1S0;
cEarth to Ocean Research Group, Department of Biological Sciences, Simon Fraser University, Burnaby, BC, Canada V5A 1S6; dRaincoast Research Society, Simoom Sound, BC, Canada V0P 1S0; eCentre for Mathematical Biology, Department of Mathematical and Statistical Sciences, Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada T6G 2G1; and fSchool of Aquatic and Fishery Sciences, University of Washington, Seattle, WA 98105
Edited by William C. Clark, Harvard University, Cambridge, MA, and approved July 27, 2011 (received for review February 2, 2011)
The ecological risks of salmon aquaculture have motivated changes to management and policy designed to protect wild salmon populations and habitats in several countries. In Canada, much attention has focused on outbreaks of parasitic copepods, sea lice (Lepeophtheirus salmonis), on farmed and wild salmon in the Broughton Archipelago, British Columbia. Several recent studies have reached contradictory conclusions on whether the spread of lice from salmon farms affects the productivity of sympatric wild salmon populations. We analyzed recently available sea lice data on farms and spawner–recruit data for pink (Oncorhynchus gorbuscha) and coho (Oncorhynchus kisutch) salmon populations in the Broughton Archipelago and nearby regions where farms are not present. Our results show that sea lice abundance on farms is negatively associated with productivity of both pink and coho salmon in the Broughton Archipelago. These results reconcile the contradictory findings of previous studies and suggest that management and policy measures designed to protect wild salmon from sea lice should yield conservation and fishery benefits.
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Epizootics of wild fish induced by farm fish
Martin Krkosˇek*†, Mark A. Lewis*, Alexandra Morton‡, L. Neil Frazer§, and John P. Volpe¶
*Centre for Mathematical Biology, Departments of Mathematical and Statistical Sciences and Biological Sciences, University of Alberta, Edmonton, AB, Canada T6G 1G1;
‡Raincoast Research Society, Simoom Sound, BC, Canada V0P 1S0; §Department of Geology and Geophysics, School of Ocean and Earth Science and Technology, University of Hawaii, 2525 Correa Road, Honolulu, HI 96822; and ¶School of Environmental Studies, University of Victoria, 3800 Finnerty Road, Victoria, BC, Canada V8P 5C2
Edited by Stephen R. Carpenter, University of Wisconsin, Madison, WI, and approved August 24, 2006 (received for review April 29, 2006)
The continuing decline of ocean fisheries and rise of global fish consumption has driven aquaculture growth by 10% annually over the last decade. The association of fish farms with disease emergence in sympatric wild fish stocks remains one of the most controversial and unresolved threats aquaculture poses to coastal ecosystems and fisheries. We report a comprehensive analysis of the spread and impact of farm-origin parasites on the survival of wild fish populations. We mathematically coupled extensive data sets of native parasitic sea lice (Lepeophtheirus salmonis) transmission and pathogenicity on migratory wild juvenile pink (Oncorhynchus gorbuscha) and chum (Oncorhynchus keta) salmon. Farm-origin lice induced 9–95% mortality in several sympatric wild juvenile pink and chum salmon populations. The epizootics arise through a mechanism that is new to our understanding of emerging infectious diseases: fish farms undermine a functional role of host migration in protecting juvenile hosts from parasites associated with adult hosts. Although the migratory life cycles of Pacific salmon naturally separate adults from juveniles, fish farms provide L. salmonis novel access to juvenile hosts, in this case raising infection rates for at least the first _2.5 months of the salmon’s marine life (_80 km of the migration route). Spatial segregation between juveniles and adults is common among temperate marine fishes, and as aquaculture continues its rapid growth, this disease mechanism may challenge the sustainability of coastal ecosystems and economies.
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Salmon lice infection of wild sea trout and Arctic char in marine and freshwaters: the effects of salmon farms
P A Bjùrn1, B Finstad2 & R Kristoffersen1
1The Norwegian College of Fishery Science. Breivika. N-9037 Tromsù, Norway
2The Norwegian Institute for Nature Research, Tungasletta 2, N-7485 Trondheim, Norway
Correspondence: P A Bjùrn, Norwegian Institute of Fisheries and Aquaculture, N-9291 Tromsù, Norway.
E-mail: paal-arne.bjorn@®skforsk.norut.no
Abstract
The abundance of salmon lice and the physiological effects of infection were examined in two stocks of sympatric sea trout and anadromous Arctic char in northern Norway. One stock feed in a coastal area with extensive salmon farming (exposed locality), while the other feed in a region with little farming activity (unexposed locality). The results showed that the lice infection was signi®cantly higher at the exposed locality, at which the mean intensity of infection peaked in June and July at over 100 and 200 lice larvae per ®sh respectively. At the exposed locality we also observed a premature return to freshwater of the most heavily infected ®sh. Such behaviour has previously been interpreted as a response by the ®sh to reduce the stress caused by the infection and/or to enhance survival. Blood samples taken from sea trout at sea at the exposed locality showed a positive correlation between intensity of parasite infection and an increase in the plasma cortisol, chloride and blood glucose concentrations, while the correlations from sea trout in freshwater were more casual. Several indices pointed towards an excessive mortality of the heaviest infected ®sh, and 47% of the ®sh caught in freshwater and 32% of those captured at sea carried lice at intensities above the level that has been shown to induce mortality in laboratory experiments. Furthermore, almost half of all ®sh from the exposed locality had lice intensities that would probably cause osmoregulatory imbalance.
Martin Krkošeka,b,1, Brendan M. Connorsb,c, Alexandra Mortonb,d, Mark A. Lewise, Lawrence M. Dillc, and Ray Hilbornf
aDepartment of Zoology, University of Otago, Dunedin, New Zealand, 9016;
bSalmon Coast Field Station, Simoom Sound, BC, Canada V0P 1S0;
cEarth to Ocean Research Group, Department of Biological Sciences, Simon Fraser University, Burnaby, BC, Canada V5A 1S6; dRaincoast Research Society, Simoom Sound, BC, Canada V0P 1S0; eCentre for Mathematical Biology, Department of Mathematical and Statistical Sciences, Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada T6G 2G1; and fSchool of Aquatic and Fishery Sciences, University of Washington, Seattle, WA 98105
Edited by William C. Clark, Harvard University, Cambridge, MA, and approved July 27, 2011 (received for review February 2, 2011)
The ecological risks of salmon aquaculture have motivated changes to management and policy designed to protect wild salmon populations and habitats in several countries. In Canada, much attention has focused on outbreaks of parasitic copepods, sea lice (Lepeophtheirus salmonis), on farmed and wild salmon in the Broughton Archipelago, British Columbia. Several recent studies have reached contradictory conclusions on whether the spread of lice from salmon farms affects the productivity of sympatric wild salmon populations. We analyzed recently available sea lice data on farms and spawner–recruit data for pink (Oncorhynchus gorbuscha) and coho (Oncorhynchus kisutch) salmon populations in the Broughton Archipelago and nearby regions where farms are not present. Our results show that sea lice abundance on farms is negatively associated with productivity of both pink and coho salmon in the Broughton Archipelago. These results reconcile the contradictory findings of previous studies and suggest that management and policy measures designed to protect wild salmon from sea lice should yield conservation and fishery benefits.
------------------------------------------------------------------------------------------------------------------------------------------------------
Epizootics of wild fish induced by farm fish
Martin Krkosˇek*†, Mark A. Lewis*, Alexandra Morton‡, L. Neil Frazer§, and John P. Volpe¶
*Centre for Mathematical Biology, Departments of Mathematical and Statistical Sciences and Biological Sciences, University of Alberta, Edmonton, AB, Canada T6G 1G1;
‡Raincoast Research Society, Simoom Sound, BC, Canada V0P 1S0; §Department of Geology and Geophysics, School of Ocean and Earth Science and Technology, University of Hawaii, 2525 Correa Road, Honolulu, HI 96822; and ¶School of Environmental Studies, University of Victoria, 3800 Finnerty Road, Victoria, BC, Canada V8P 5C2
Edited by Stephen R. Carpenter, University of Wisconsin, Madison, WI, and approved August 24, 2006 (received for review April 29, 2006)
The continuing decline of ocean fisheries and rise of global fish consumption has driven aquaculture growth by 10% annually over the last decade. The association of fish farms with disease emergence in sympatric wild fish stocks remains one of the most controversial and unresolved threats aquaculture poses to coastal ecosystems and fisheries. We report a comprehensive analysis of the spread and impact of farm-origin parasites on the survival of wild fish populations. We mathematically coupled extensive data sets of native parasitic sea lice (Lepeophtheirus salmonis) transmission and pathogenicity on migratory wild juvenile pink (Oncorhynchus gorbuscha) and chum (Oncorhynchus keta) salmon. Farm-origin lice induced 9–95% mortality in several sympatric wild juvenile pink and chum salmon populations. The epizootics arise through a mechanism that is new to our understanding of emerging infectious diseases: fish farms undermine a functional role of host migration in protecting juvenile hosts from parasites associated with adult hosts. Although the migratory life cycles of Pacific salmon naturally separate adults from juveniles, fish farms provide L. salmonis novel access to juvenile hosts, in this case raising infection rates for at least the first _2.5 months of the salmon’s marine life (_80 km of the migration route). Spatial segregation between juveniles and adults is common among temperate marine fishes, and as aquaculture continues its rapid growth, this disease mechanism may challenge the sustainability of coastal ecosystems and economies.
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Salmon lice infection of wild sea trout and Arctic char in marine and freshwaters: the effects of salmon farms
P A Bjùrn1, B Finstad2 & R Kristoffersen1
1The Norwegian College of Fishery Science. Breivika. N-9037 Tromsù, Norway
2The Norwegian Institute for Nature Research, Tungasletta 2, N-7485 Trondheim, Norway
Correspondence: P A Bjùrn, Norwegian Institute of Fisheries and Aquaculture, N-9291 Tromsù, Norway.
E-mail: paal-arne.bjorn@®skforsk.norut.no
Abstract
The abundance of salmon lice and the physiological effects of infection were examined in two stocks of sympatric sea trout and anadromous Arctic char in northern Norway. One stock feed in a coastal area with extensive salmon farming (exposed locality), while the other feed in a region with little farming activity (unexposed locality). The results showed that the lice infection was signi®cantly higher at the exposed locality, at which the mean intensity of infection peaked in June and July at over 100 and 200 lice larvae per ®sh respectively. At the exposed locality we also observed a premature return to freshwater of the most heavily infected ®sh. Such behaviour has previously been interpreted as a response by the ®sh to reduce the stress caused by the infection and/or to enhance survival. Blood samples taken from sea trout at sea at the exposed locality showed a positive correlation between intensity of parasite infection and an increase in the plasma cortisol, chloride and blood glucose concentrations, while the correlations from sea trout in freshwater were more casual. Several indices pointed towards an excessive mortality of the heaviest infected ®sh, and 47% of the ®sh caught in freshwater and 32% of those captured at sea carried lice at intensities above the level that has been shown to induce mortality in laboratory experiments. Furthermore, almost half of all ®sh from the exposed locality had lice intensities that would probably cause osmoregulatory imbalance.
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 infectionfree 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.
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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.
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Sea Louse Infestation in Wild Juvenile Salmon and Pacific Herring Associated with Fish Farms off the East-Central Coast of Vancouver Island, British Columbia
ALEXANDRA MORTON
Raincoast Research Society, Simoom Sound, British Columbia V0P 1S0, Canada
RICK ROUTLEDGE
Department of Statistics and Actuarial Science, Simon Fraser University,
8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada
MARTIN KRKOSˇ EK
Centre for Mathematical Biology, Department of Biological Sciences, 632 Central Academic Building,
University of Alberta, Edmonton, Alberta T6G 2G1, Canada
Abstract.—Reports of infestations of sea lice Lepeophtheirus salmonis and Caligus clemensi in juvenile salmonids in Pacific Canada have been restricted to pink salmon Oncorhynchus gorbuscha and chum salmon O. keta from one salmon-farming region, the Broughton Archipelago of British Columbia. Here, we report on 2 years of sea louse field surveys of wild juvenile pink and chum salmon, as well as wild sockeye salmon O. nerka and larval Pacific herring Clupea pallasii, in another salmon farming region, the Discovery Islands region of British Columbia. For pink and chum salmon we tested for the dependency of sea louse abundance on temperature, salinity, sampling period, host species, and farm exposure category. For both louse species, farm exposure was the only consistently significant predictor of sea lice abundance. Fish exposed to salmon farms were infected with more sea lice than those in the peripheral category. Sea louse abundance on sockeye salmon and Pacific herring followed the same trends, but sample sizes were too low to support formal statistical analysis. The Pacific herring were translucent and lacked scales, and they were primarily parasitized by C. clemensi. These results suggest that the association of salmon farms with sea lice infestations of wild juvenile fish in Pacific Canada now extends beyond juvenile pink and chum salmon in the Broughton Archipelago. Canada’s most abundant and economically valuable salmon populations, as well as British Columbia’s most valuable Pacific herring stock, migrate through the Discovery Islands; hence, parasite transmission from farm to wild fish in this region may have important economic and ecological implications.
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 infectionfree 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.
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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.
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Sea Louse Infestation in Wild Juvenile Salmon and Pacific Herring Associated with Fish Farms off the East-Central Coast of Vancouver Island, British Columbia
ALEXANDRA MORTON
Raincoast Research Society, Simoom Sound, British Columbia V0P 1S0, Canada
RICK ROUTLEDGE
Department of Statistics and Actuarial Science, Simon Fraser University,
8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada
MARTIN KRKOSˇ EK
Centre for Mathematical Biology, Department of Biological Sciences, 632 Central Academic Building,
University of Alberta, Edmonton, Alberta T6G 2G1, Canada
Abstract.—Reports of infestations of sea lice Lepeophtheirus salmonis and Caligus clemensi in juvenile salmonids in Pacific Canada have been restricted to pink salmon Oncorhynchus gorbuscha and chum salmon O. keta from one salmon-farming region, the Broughton Archipelago of British Columbia. Here, we report on 2 years of sea louse field surveys of wild juvenile pink and chum salmon, as well as wild sockeye salmon O. nerka and larval Pacific herring Clupea pallasii, in another salmon farming region, the Discovery Islands region of British Columbia. For pink and chum salmon we tested for the dependency of sea louse abundance on temperature, salinity, sampling period, host species, and farm exposure category. For both louse species, farm exposure was the only consistently significant predictor of sea lice abundance. Fish exposed to salmon farms were infected with more sea lice than those in the peripheral category. Sea louse abundance on sockeye salmon and Pacific herring followed the same trends, but sample sizes were too low to support formal statistical analysis. The Pacific herring were translucent and lacked scales, and they were primarily parasitized by C. clemensi. These results suggest that the association of salmon farms with sea lice infestations of wild juvenile fish in Pacific Canada now extends beyond juvenile pink and chum salmon in the Broughton Archipelago. Canada’s most abundant and economically valuable salmon populations, as well as British Columbia’s most valuable Pacific herring stock, migrate through the Discovery Islands; hence, parasite transmission from farm to wild fish in this region may have important economic and ecological implications.
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Sea lice (Lepeophtheirus salmonis) infection rates on juvenile pink (Oncorhynchus gorbuscha) and chum (Oncorhynchus keta) salmon in the nearshore marine environment of British Columbia, Canada
Alexandra Morton, Richard Routledge, Corey Peet, and Aleria Ladwig
Abstract: This study compared sea lice (Lepeophtheirus salmonis) infestation rates on juvenile pink (Oncorhynchus gorbuscha) and chum (Oncorhynchus keta) salmon in five nearshore areas of the British Columbia coast selected on the basis of proximity to salmon farms. A 10-week study in the Broughton Archipelago found sea lice were 8.8 times more abundant on wild fish near farms holding adult salmon and 5.0 times more abundant on wild fish near farms holding smolts than in areas distant from salmon farms. We found that 90% of juvenile pink and chum salmon sampled near salmon farms in the Broughton Archipelago were infected with more than 1.6 lice·(g host mass)–1, a proposed lethal limit when the lice reach mobile stages. Sea lice abundance was near zero in all areas without salmon farms. Salinity and temperature differences could not account for the higher infestation rates near the fish farms. The most immature life stages dominated the lice population throughout the study, suggesting the source of lice was a stationary, local salmonid population. No such wild population could be identified. The evidence from this control–impact study points to a relationship between salmon farms and sea lice on adjacent, wild, juvenile salmon.
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Coho salmon productivity in relation to salmon lice from infected prey and salmon farms
Brendan M. Connors1*, Martin Krkosˇ ek2,3, Jennifer Ford4 and Lawrence M. Dill1
1Earth to Ocean and Evolutionary and Behavioural Ecology Research Groups, Department of Biological Sciences, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada;
2School of Aquatic and Fishery Sciences, University of Washington, 1122 NE Boat St, Seattle, WA 98105, USA;
3Department of Zoology, University of Otago, PO Box 56, Dunedin 9054, New Zealand; and
4Oceans and Coastal Management Division, Bedford Institute of Oceanography, Fisheries and Oceans Canada, Dartmouth, NS B2Y 4A2, Canada
Summary
1. Pathogen transmission from open net-pen aquaculture facilities can depress sympatric wild fish populations. However, little is known about the effects of pathogen transmission from farmed fish on species interactions or other ecosystem components. Coho salmon Oncorhynchus kisutch smolts are susceptible hosts to the parasitic salmon louse Lepeophtheirus salmonis as well as a primary predator of juvenile pink Oncorhynchus gorbuscha salmon, a major host species for lice.
2. We used a hierarchical model of stock-recruit dynamics to compare coho salmon population dynamics across a region that varies in salmon louse infestation of juvenile coho and their pink salmon prey.
3. During a period of recurring salmon louse infestations in a region of open net-pen salmon farms, coho salmon productivity (recruits per spawner at low spawner abundance) was depressed approximately sevenfold relative to unexposed populations. Alternate hypotheses for the observed difference in productivity, such as declines in coho prey, perturbations to freshwater habitat or stochasticity, are unlikely to explain this pattern.
4. Lice parasitizing juvenile coho salmon were likely to be trophically transmitted during predation on parasitized juvenile pink salmon as well as directly transmitted fromsalmon farms.
5. Synthesis and applications. The finding that species interactions may cause the effects of pathogen transmission from farmed to wild fish to propagate up a marine food web has important conservation implications: (i) the management of salmon aquaculture should consider and account for species interactions and the potential for these interactions to intensify pathogen transmission from farmed to wild fish, (ii) the ecosystem impact of louse transmission from farmed to wild salmon has likely to have been previously underestimated and (iii) comprehensive monitoring of wild salmon and their population dynamics in areas of intensive salmon aquaculture should be a priority to determine if open net-pen salmon aquaculture is ecologically sustainable.
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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.
Alexandra Morton, Richard Routledge, Corey Peet, and Aleria Ladwig
Abstract: This study compared sea lice (Lepeophtheirus salmonis) infestation rates on juvenile pink (Oncorhynchus gorbuscha) and chum (Oncorhynchus keta) salmon in five nearshore areas of the British Columbia coast selected on the basis of proximity to salmon farms. A 10-week study in the Broughton Archipelago found sea lice were 8.8 times more abundant on wild fish near farms holding adult salmon and 5.0 times more abundant on wild fish near farms holding smolts than in areas distant from salmon farms. We found that 90% of juvenile pink and chum salmon sampled near salmon farms in the Broughton Archipelago were infected with more than 1.6 lice·(g host mass)–1, a proposed lethal limit when the lice reach mobile stages. Sea lice abundance was near zero in all areas without salmon farms. Salinity and temperature differences could not account for the higher infestation rates near the fish farms. The most immature life stages dominated the lice population throughout the study, suggesting the source of lice was a stationary, local salmonid population. No such wild population could be identified. The evidence from this control–impact study points to a relationship between salmon farms and sea lice on adjacent, wild, juvenile salmon.
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Coho salmon productivity in relation to salmon lice from infected prey and salmon farms
Brendan M. Connors1*, Martin Krkosˇ ek2,3, Jennifer Ford4 and Lawrence M. Dill1
1Earth to Ocean and Evolutionary and Behavioural Ecology Research Groups, Department of Biological Sciences, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada;
2School of Aquatic and Fishery Sciences, University of Washington, 1122 NE Boat St, Seattle, WA 98105, USA;
3Department of Zoology, University of Otago, PO Box 56, Dunedin 9054, New Zealand; and
4Oceans and Coastal Management Division, Bedford Institute of Oceanography, Fisheries and Oceans Canada, Dartmouth, NS B2Y 4A2, Canada
Summary
1. Pathogen transmission from open net-pen aquaculture facilities can depress sympatric wild fish populations. However, little is known about the effects of pathogen transmission from farmed fish on species interactions or other ecosystem components. Coho salmon Oncorhynchus kisutch smolts are susceptible hosts to the parasitic salmon louse Lepeophtheirus salmonis as well as a primary predator of juvenile pink Oncorhynchus gorbuscha salmon, a major host species for lice.
2. We used a hierarchical model of stock-recruit dynamics to compare coho salmon population dynamics across a region that varies in salmon louse infestation of juvenile coho and their pink salmon prey.
3. During a period of recurring salmon louse infestations in a region of open net-pen salmon farms, coho salmon productivity (recruits per spawner at low spawner abundance) was depressed approximately sevenfold relative to unexposed populations. Alternate hypotheses for the observed difference in productivity, such as declines in coho prey, perturbations to freshwater habitat or stochasticity, are unlikely to explain this pattern.
4. Lice parasitizing juvenile coho salmon were likely to be trophically transmitted during predation on parasitized juvenile pink salmon as well as directly transmitted fromsalmon farms.
5. Synthesis and applications. The finding that species interactions may cause the effects of pathogen transmission from farmed to wild fish to propagate up a marine food web has important conservation implications: (i) the management of salmon aquaculture should consider and account for species interactions and the potential for these interactions to intensify pathogen transmission from farmed to wild fish, (ii) the ecosystem impact of louse transmission from farmed to wild salmon has likely to have been previously underestimated and (iii) comprehensive monitoring of wild salmon and their population dynamics in areas of intensive salmon aquaculture should be a priority to determine if open net-pen salmon aquaculture is ecologically sustainable.
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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.
fogged in
Well-Known Member
I am guessing the post by agentaqua will result in no further response from Dave or the other Fish Farm Supporters
Darn...just when they were about to confirm their that in their opinion Fish Farms Sea Lice do or do not Kill Wild Salmon
Still hoping for a short and direct answer to my question
What do you think my chance of a simple yes or no answer to my question????
Sea lice, sockeye salmon, and foraging competition: lousy fish are lousy competitors
Sean C. Godwin, Lawrence M. Dill, John D. Reynolds, and Martin Krkošek
Abstract: Pathogens threaten wildlife globally, but these impacts are not restricted to direct mortality from disease. For fish, which experience periods of extremely high mortality during their early life history, infections may primarily influence population dynamics and conservation through indirect effects on ecological processes such as competition and predation.Weconducted a competitive foraging experiment using outmigrating juvenile Fraser River sockeye salmon (Oncorhynchus nerka) to determine whether fish with high abundances of parasitic sea lice (Caligus clemensi and Lepeophtheirus salmonis) have reduced competitive abilities when foraging. Highly infected sockeye were 20% less successful at consuming food, on average, than lightly infected fish. Competitive ability also increased with fish body size. Our results provide the first evidence that parasite exposure may have negative indirect effects on the fitness of juvenile sockeye salmon and suggest that indirect effects of pathogens may be of key importance for the conservation of marine fish.
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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, C Carr-Harris1
1 Skeena Fisheries Commission, Hazelton, British Columbia
2 Oona River Resources Association, Prince Rupert, British Columbia
All correspondence to be directed to A. S. Gottesfeld, Skeena Fisheries Commission, PO Box 166, 1525A Hankin Street, Hazelton, British Columbia V0J 1Y0 e-mail: gottesfeld@skeenafisheries.ca
Keywords: Lepeophtheirus salmonis, sea lice on wild salmon, pink salmon, Chinook salmon, sea lice epizootiology2
Abstract
We examined sea lice (Lepeophtheirus salmonis) on juvenile and adult salmon of 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 (O. tshawytscha) and coho salmon (O. 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.
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Space-Time Modelling of the Spread of Salmon Lice between and within Norwegian Marine Salmon Farms
Magne Aldrin1,2*, Ba°rd Storvik1, Anja Bra°then Kristoffersen3,4, Peder Andreas Jansen3
1 Norwegian Computing Center, Oslo, Norway,
2 Department of Mathematics, University of Oslo, Oslo, Norway,
3 Norwegian Veterinary Institute, Oslo, Norway,
4 Department of Informatics, University of Oslo, Oslo, Norway
Abstract
Parasitic salmon lice are potentially harmful to salmonid hosts and farm produced lice pose a threat to wild salmonids. To control salmon lice infections in Norwegian salmonid farming, numbers of lice are regularly counted and lice abundance is reported from all salmonid farms every month. We have developed a stochastic space-time model where monthly lice abundance is modelled simultaneously for all farms. The set of farms is regarded as a network where the degree of contact between farms depends on their seaway distance. The expected lice abundance at each farm is modelled as a function of i) lice abundance in previous months at the same farm, ii) at neighbourhood farms, and iii) other, unspecified sources. In addition, the model includes explanatory variables such as seawater temperature and farm-numbers of fish. The model gives insight into factors that affect salmon lice abundance and contributing sources of infection. New findings in this study were that 66% of the expected salmon lice abundance was attributed to infection within farms, 28% was attributed to infection from neighbourhood farms and 6% to non-specified sources of infection. Furthermore, we present the relative risk of infection between neighbourhood farms as a function of seaway distance, which can be viewed as a between farm transmission kernel for salmon lice. The present modelling framework lays the foundation for development of future scenario simulation tools for examining the spread and abundance of salmon lice on farmed salmonids under different control regimes
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Sea lice in Loch Torridon, Western Scotland: planktonic distribution, interactions with sea trout, larval transport modelling and the impacts of fish farms.
M.A. McKibben, P.A. Gillibrand, D.W. Hay, S. Murray & M.J. Penston.
Abstract
Sea trout, Salmo trutta, numbers on the west coast of Scotland have fallen over the last thirty years. This decline has been linked to reduced survival in the marine phase. Lice infection may have a detrimental impact on the survival of wild smolts soon after seawater transfer. Plankton samples collected over the last five years from near shore and offshore sites have shown higher levels of sea lice copepodids in the second half of the salmon farm production cycle. Very high levels of sea lice copepodids were found in near shore areas (> 100 m-3). Such high levels of copepodids have not been recorded previously outside fish farm cages. This study also showed a seasonal cycle of larval sea lice abundance in samples taken weekly for over three years which closely matched the local fish farm production cycle and sea lice infestation rates on the farm. A particle tracking model has been produced for Loch Torridon which tracks the movements of passive particles in the surface layer using simulated advection and diffuse currents. The model indicates that the area of highest risk is often several km from the source farm. Early returning post smolt sea trout (Salmo trutta) are a phenomenon that has been studied since the late 1980's. In the River Shieldaig in western Scotland a sea trout trap has allowed this phenomenon to be studied in detail. The presence and absence of early returning post smolts and the level of sea lice infection were examined over five years and the results related to the stage of the local fish farm production cycle. The results indicate that early returning sea trout smolts with high numbers of sea lice are mainly seen in the second year of the production cycle and are very low in the first year of production when ovigerous lice levels on local salmon farms are zero.
Sean C. Godwin, Lawrence M. Dill, John D. Reynolds, and Martin Krkošek
Abstract: Pathogens threaten wildlife globally, but these impacts are not restricted to direct mortality from disease. For fish, which experience periods of extremely high mortality during their early life history, infections may primarily influence population dynamics and conservation through indirect effects on ecological processes such as competition and predation.Weconducted a competitive foraging experiment using outmigrating juvenile Fraser River sockeye salmon (Oncorhynchus nerka) to determine whether fish with high abundances of parasitic sea lice (Caligus clemensi and Lepeophtheirus salmonis) have reduced competitive abilities when foraging. Highly infected sockeye were 20% less successful at consuming food, on average, than lightly infected fish. Competitive ability also increased with fish body size. Our results provide the first evidence that parasite exposure may have negative indirect effects on the fitness of juvenile sockeye salmon and suggest that indirect effects of pathogens may be of key importance for the conservation of marine fish.
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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, C Carr-Harris1
1 Skeena Fisheries Commission, Hazelton, British Columbia
2 Oona River Resources Association, Prince Rupert, British Columbia
All correspondence to be directed to A. S. Gottesfeld, Skeena Fisheries Commission, PO Box 166, 1525A Hankin Street, Hazelton, British Columbia V0J 1Y0 e-mail: gottesfeld@skeenafisheries.ca
Keywords: Lepeophtheirus salmonis, sea lice on wild salmon, pink salmon, Chinook salmon, sea lice epizootiology2
Abstract
We examined sea lice (Lepeophtheirus salmonis) on juvenile and adult salmon of 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 (O. tshawytscha) and coho salmon (O. 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.
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Space-Time Modelling of the Spread of Salmon Lice between and within Norwegian Marine Salmon Farms
Magne Aldrin1,2*, Ba°rd Storvik1, Anja Bra°then Kristoffersen3,4, Peder Andreas Jansen3
1 Norwegian Computing Center, Oslo, Norway,
2 Department of Mathematics, University of Oslo, Oslo, Norway,
3 Norwegian Veterinary Institute, Oslo, Norway,
4 Department of Informatics, University of Oslo, Oslo, Norway
Abstract
Parasitic salmon lice are potentially harmful to salmonid hosts and farm produced lice pose a threat to wild salmonids. To control salmon lice infections in Norwegian salmonid farming, numbers of lice are regularly counted and lice abundance is reported from all salmonid farms every month. We have developed a stochastic space-time model where monthly lice abundance is modelled simultaneously for all farms. The set of farms is regarded as a network where the degree of contact between farms depends on their seaway distance. The expected lice abundance at each farm is modelled as a function of i) lice abundance in previous months at the same farm, ii) at neighbourhood farms, and iii) other, unspecified sources. In addition, the model includes explanatory variables such as seawater temperature and farm-numbers of fish. The model gives insight into factors that affect salmon lice abundance and contributing sources of infection. New findings in this study were that 66% of the expected salmon lice abundance was attributed to infection within farms, 28% was attributed to infection from neighbourhood farms and 6% to non-specified sources of infection. Furthermore, we present the relative risk of infection between neighbourhood farms as a function of seaway distance, which can be viewed as a between farm transmission kernel for salmon lice. The present modelling framework lays the foundation for development of future scenario simulation tools for examining the spread and abundance of salmon lice on farmed salmonids under different control regimes
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Sea lice in Loch Torridon, Western Scotland: planktonic distribution, interactions with sea trout, larval transport modelling and the impacts of fish farms.
M.A. McKibben, P.A. Gillibrand, D.W. Hay, S. Murray & M.J. Penston.
Abstract
Sea trout, Salmo trutta, numbers on the west coast of Scotland have fallen over the last thirty years. This decline has been linked to reduced survival in the marine phase. Lice infection may have a detrimental impact on the survival of wild smolts soon after seawater transfer. Plankton samples collected over the last five years from near shore and offshore sites have shown higher levels of sea lice copepodids in the second half of the salmon farm production cycle. Very high levels of sea lice copepodids were found in near shore areas (> 100 m-3). Such high levels of copepodids have not been recorded previously outside fish farm cages. This study also showed a seasonal cycle of larval sea lice abundance in samples taken weekly for over three years which closely matched the local fish farm production cycle and sea lice infestation rates on the farm. A particle tracking model has been produced for Loch Torridon which tracks the movements of passive particles in the surface layer using simulated advection and diffuse currents. The model indicates that the area of highest risk is often several km from the source farm. Early returning post smolt sea trout (Salmo trutta) are a phenomenon that has been studied since the late 1980's. In the River Shieldaig in western Scotland a sea trout trap has allowed this phenomenon to be studied in detail. The presence and absence of early returning post smolts and the level of sea lice infection were examined over five years and the results related to the stage of the local fish farm production cycle. The results indicate that early returning sea trout smolts with high numbers of sea lice are mainly seen in the second year of the production cycle and are very low in the first year of production when ovigerous lice levels on local salmon farms are zero.
Infection with low numbers of the sea louse Lepeophtheirus salmonis induces stress-related effects in postsmolt Atlantic salmon (Salmo salar)
D.T. Nolan, P. Reilly, and S.E. Wendelaar Bonga
Abstract: Infection of postsmolt Atlantic salmon (Salmo salar) with three, six, or 10 preadult and adult sea lice (Lepeophtheirus salmonis) per fish resulted in changes to epithelial structure and at sites in the skin and gill, distant from lice attachment and feeding. In the skin, increased apoptosis and necrosis occurred in the superficial epithelial cells and numbers of mucous cells decreased. In the gill, where no lice were found, uplifting of the epithelium, intercellular swelling, and infiltration by leukocytes occurred in filaments and lamellae. High cell turnover of chloride cells was associated with significantly elevated gill Na+/K+-ATPase activities. Serum chloride levels were elevated in the 3 and 6 lice/fish groups, and the serum Na to Cl ratio was lower in all parasitized groups at 5 days. The results indicate that infection with low numbers of the preadult and adult parasite induced changes characteristic of a stress response. In the low- and medium-infested groups, homeostatic recovery had occurred by 10 days, but recovery was incomplete in the highly infected group. Thus, 10 lice per fish, which is a low infestation level in nature, is stressful and creates a long period during which the overall condition of the skin and gill epithelia may render the fish susceptible to secondary infections.
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Estimated Sea Louse Egg Production from Marine Harvest Canada Farmed Atlantic Salmon in the 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.
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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.
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Cessation of a salmon decline with control of parasites
STEPHANIE J. PEACOCK,1,2,6 MARTIN KRKOSˇEK,3,4 STAN PROBOSZCZ,5 CRAIG ORR,5 AND MARK A. LEWIS1,2
1Department of Biological Sciences, University of Alberta, Edmonton, Alberta T6G 2G1 Canada
2Centre for Mathematical Biology, Department of Mathematical and Statistical Sciences, University of Alberta, Edmonton, Alberta T6G 2G1 Canada
3Department of Zoology, University of Otago, Dunedin, New Zealand
4Salmon Coast Field Station, Simoom Sound, British Columbia V0P 1S0 Canada
5Watershed Watch Salmon Society, Coquitlam, British Columbia V3K 3B7 Canada
Abstract. The resilience of coastal social–ecological systems may depend on adaptive responses to aquaculture disease outbreaks that can threaten wild and farm fish. A nine-year study of parasitic sea lice (Lepeophtheirus salmonis) and pink salmon (Oncorhynchus gorbuscha) from Pacific Canada indicates that adaptive changes in parasite management on salmon farms have yielded positive conservation outcomes. After four years of sea lice epizootics and wild salmon population decline, parasiticide application on salmon farms was adapted to the timing of wild salmon migrations. Winter treatment of farm fish with parasiticides, prior to the out-migration of wild juvenile salmon, has reduced epizootics of wild salmon without significantly increasing the annual number of treatments. Levels of parasites on wild juvenile salmon significantly influence the growth rate of affected salmon populations, suggesting that these changes in management have had positive outcomes for wild salmon populations. These adaptive changes have not occurred through formal adaptive management, but rather, through multi-stakeholder processes arising from a contentious scientific and public debate. Despite the apparent success of parasite control on salmon farms in the study region, there remain concerns about the long-term sustainability of this approach because of the unknown ecological effects of parasticides and the potential for parasite resistance to chemical treatments.
D.T. Nolan, P. Reilly, and S.E. Wendelaar Bonga
Abstract: Infection of postsmolt Atlantic salmon (Salmo salar) with three, six, or 10 preadult and adult sea lice (Lepeophtheirus salmonis) per fish resulted in changes to epithelial structure and at sites in the skin and gill, distant from lice attachment and feeding. In the skin, increased apoptosis and necrosis occurred in the superficial epithelial cells and numbers of mucous cells decreased. In the gill, where no lice were found, uplifting of the epithelium, intercellular swelling, and infiltration by leukocytes occurred in filaments and lamellae. High cell turnover of chloride cells was associated with significantly elevated gill Na+/K+-ATPase activities. Serum chloride levels were elevated in the 3 and 6 lice/fish groups, and the serum Na to Cl ratio was lower in all parasitized groups at 5 days. The results indicate that infection with low numbers of the preadult and adult parasite induced changes characteristic of a stress response. In the low- and medium-infested groups, homeostatic recovery had occurred by 10 days, but recovery was incomplete in the highly infected group. Thus, 10 lice per fish, which is a low infestation level in nature, is stressful and creates a long period during which the overall condition of the skin and gill epithelia may render the fish susceptible to secondary infections.
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Estimated Sea Louse Egg Production from Marine Harvest Canada Farmed Atlantic Salmon in the 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.
------------------------------------------------------------------------------------------------------------------------------------------------------
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.
-----------------------------------------------------------------------------------------------------------------------------------------------------
Cessation of a salmon decline with control of parasites
STEPHANIE J. PEACOCK,1,2,6 MARTIN KRKOSˇEK,3,4 STAN PROBOSZCZ,5 CRAIG ORR,5 AND MARK A. LEWIS1,2
1Department of Biological Sciences, University of Alberta, Edmonton, Alberta T6G 2G1 Canada
2Centre for Mathematical Biology, Department of Mathematical and Statistical Sciences, University of Alberta, Edmonton, Alberta T6G 2G1 Canada
3Department of Zoology, University of Otago, Dunedin, New Zealand
4Salmon Coast Field Station, Simoom Sound, British Columbia V0P 1S0 Canada
5Watershed Watch Salmon Society, Coquitlam, British Columbia V3K 3B7 Canada
Abstract. The resilience of coastal social–ecological systems may depend on adaptive responses to aquaculture disease outbreaks that can threaten wild and farm fish. A nine-year study of parasitic sea lice (Lepeophtheirus salmonis) and pink salmon (Oncorhynchus gorbuscha) from Pacific Canada indicates that adaptive changes in parasite management on salmon farms have yielded positive conservation outcomes. After four years of sea lice epizootics and wild salmon population decline, parasiticide application on salmon farms was adapted to the timing of wild salmon migrations. Winter treatment of farm fish with parasiticides, prior to the out-migration of wild juvenile salmon, has reduced epizootics of wild salmon without significantly increasing the annual number of treatments. Levels of parasites on wild juvenile salmon significantly influence the growth rate of affected salmon populations, suggesting that these changes in management have had positive outcomes for wild salmon populations. These adaptive changes have not occurred through formal adaptive management, but rather, through multi-stakeholder processes arising from a contentious scientific and public debate. Despite the apparent success of parasite control on salmon farms in the study region, there remain concerns about the long-term sustainability of this approach because of the unknown ecological effects of parasticides and the potential for parasite resistance to chemical treatments.
Well done aa.
So, which Pacific stock has been measurably impacted by salmon farms here in BC? All I can see in all those titles were possibly juvenile pinks from the Broughton area that appeared to have lice infestations. Likely some of those died before being sampled but, how have those stocks done since those studies?
So, which Pacific stock has been measurably impacted by salmon farms here in BC? All I can see in all those titles were possibly juvenile pinks from the Broughton area that appeared to have lice infestations. Likely some of those died before being sampled but, how have those stocks done since those studies?
fogged in
Well-Known Member
g
Now lets just agree that Fish Farm Sea Lice do kill wild salmon.
We all know Fish Farms are fighting the Sea Lice problem world wide with variable success and results will vary greatly from year to year and area to area.
Fish Farms are not the only problem with the decline in wild salmon, but if we are going to solve the problem, Fish Farms must recognize they are part of the problem!!
Lets hear from the rest of the Fish Farm guys with their opinions.....no more useless rhetoric and deflections
Good on you Dave for at least a partial recognition of the Fish Farm problem
Now lets just agree that Fish Farm Sea Lice do kill wild salmon.
We all know Fish Farms are fighting the Sea Lice problem world wide with variable success and results will vary greatly from year to year and area to area.
Fish Farms are not the only problem with the decline in wild salmon, but if we are going to solve the problem, Fish Farms must recognize they are part of the problem!!
Lets hear from the rest of the Fish Farm guys with their opinions.....no more useless rhetoric and deflections
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the broughton has been killing pink salmon for years, long before a fish farm showed up. if you really read science you will see a paper peoduced that shows sea lice counts rise and decline on in coming and out going pink years. further more, same paper explains why. pink salmon are the worst carriers of sea lice because of there 2 year cycle. they do not live long enough to develop anti bodies to resist sea lice. one can say that wild pink salmon are actually the problem.
Pink salmon are the problem? really? Interesting claim. well I guess then that Europe shouldn't have any sea lice problems, them - no pink salmon - way fewer wild salmon. Wait a minute...
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