Comment on "Declining Wild Salmon Populations in Relation to Parasites from Farm Salmon"

Krkošek et al. (Reports, 14 December 2007, p. 1772) claimed that sea lice spread from salmon farms placed wild pink salmon populations “on a trajectory toward rapid local extinction.” Their prediction is inconsistent with observed pink salmon returns and overstates the risks from sea lice and salmon farming.

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Response to Comment on "Declining Wild Salmon Populations in Relation to Parasites from Farm Salmon"

Science ◽

10.1126/science.1156578 ◽

2008 ◽

Vol 322 (5909) ◽

pp. 1790.3-1790 ◽

Cited By ~ 8

Author(s):

Martin Krkošek ◽

Jennifer S. Ford ◽

Alexandra Morton ◽

Subhash Lele ◽

Mark A. Lewis

Keyword(s):

British Columbia ◽

Pink Salmon ◽

Sea Lice ◽

Oncorhynchus Gorbuscha ◽

Lepeophtheirus Salmonis ◽

Wild Salmon ◽

Farm Salmon

We evaluated the effect of sea lice (Lepeophtheirus salmonis) infestations on wild pink salmon (Oncorhynchus gorbuscha) populations in the Broughton Archipelago, British Columbia. Riddell et al. suggest that we ignored factors and selectively used data. Here, we clarify misunderstandings and provide analysis to test the strength of our conclusions.

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Evidence of farm-induced parasite infestations on wild juvenile salmon in multiple regions of coastal British Columbia, Canada

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f10-105 ◽

2010 ◽

Vol 67 (12) ◽

pp. 1925-1932 ◽

Cited By ~ 22

Author(s):

M. H.H. Price ◽

A. Morton ◽

J. D. Reynolds

Keyword(s):

British Columbia ◽

Pink Salmon ◽

Fish Host ◽

Sea Lice ◽

Oncorhynchus Gorbuscha ◽

Oncorhynchus Keta ◽

High Exposure ◽

Salmon Farming ◽

Multiple Regions ◽

Low Exposure

Salmon farms are spatially concentrated reservoirs of fish host populations that can disrupt natural salmonid host–parasite dynamics. Sea lice frequently infect farm salmon and parasitize sympatric wild juvenile salmonids, with negative impacts on survival in Europe and Pacific Canada. We examined louse parasitism of wild juvenile chum salmon ( Oncorhynchus keta ) and pink salmon ( Oncorhynchus gorbuscha ) from three salmon farming regions in British Columbia (Finlayson, Broughton Archipelago, and Georgia Strait). We compared sites of low and high exposure to farms and included an area without farms (Bella Bella) to assess baseline infection levels. Louse prevalence and abundance were lowest and most similar to natural baseline levels at low-exposure sites and highest at high-exposure sites in all farm regions. A significantly greater proportion of the lice were Lepeophtheirus salmonis at high-exposure sites. Exposure to salmon farms was the only consistently significant factor to explain the variation in prevalence data, with a secondary role played by salinity. Our results support the hypothesis that salmon farms are a major source of sea lice on juvenile wild salmon in salmon farming regions and underscore the importance of using management techniques that mitigate threats to wild stocks.

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Relationship of farm salmon, sea lice, and wild salmon populations

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1009573108 ◽

2010 ◽

Vol 107 (52) ◽

pp. 22599-22604 ◽

Cited By ~ 64

Author(s):

G. D. Marty ◽

S. M. Saksida ◽

T. J. Quinn

Keyword(s):

Sea Lice ◽

Wild Salmon ◽

Farm Salmon ◽

Relationship Of

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Recent failure to control sea louse outbreaks on salmon in the Broughton Archipelago, British Columbia

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/cjfas-2016-0122 ◽

2016 ◽

Vol 73 (8) ◽

pp. 1164-1172 ◽

Cited By ~ 15

Author(s):

Andrew W. Bateman ◽

Stephanie J. Peacock ◽

Brendan Connors ◽

Zephyr Polk ◽

Dana Berg ◽

...

Keyword(s):

British Columbia ◽

Environmental Conditions ◽

Sea Lice ◽

Oncorhynchus Gorbuscha ◽

Effective Control ◽

Juvenile Salmon ◽

Data Set ◽

Wild Salmon ◽

Salmon Farming ◽

Farmed Salmon

The advent and growth of salmon farming has changed the epidemiology of some salmon diseases. In 2015, in the salmon-farming region of the Broughton Archipelago, British Columbia, an outbreak of native ectoparasitic copepods (sea lice; Lepeophtheirus salmonis) recurred in wild juvenile salmon after a decade of effective control. We draw on a 15-year data set of sea lice on wild and farmed salmon in the area to assess the evidence for four factors that may explain the recent outbreak: (i) poorly timed parasiticide treatments of farmed salmon relative to wild salmon migration, (ii) evolution of resistance to parasiticide treatments in sea lice, (iii) anomalous environmental conditions promoting louse population growth, and (iv) a high influx of lice with an abundant pink salmon (Oncorhynchus gorbuscha) return in 2014. We propose that a combination of poorly timed treatments and warm environmental conditions likely explains the outbreak. Where wild salmon conservation is a concern, a more effective approach to managing sea lice on wild and farmed salmon could incorporate the out-migration timing of wild juvenile salmon and information on environmental conditions.

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“Even the Evil Need a Place to Live”: Wild Salmon, Salmon Farming, and Zoning of the Icelandic Coastline

Fisheries ◽

10.1577/1548-8446-34.10.477 ◽

2009 ◽

Vol 34 (10) ◽

pp. 477-486 ◽

Cited By ~ 6

Author(s):

Sigurdur Gudjonsson ◽

Dennis L. Scarnecchia

Keyword(s):

Wild Salmon ◽

Salmon Farming

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Sea-louse abundance on salmon farms in relation to parasite-control policy and climate change

ICES Journal of Marine Science ◽

10.1093/icesjms/fsaa173 ◽

2020 ◽

Author(s):

Sean C Godwin ◽

Martin Krkosek ◽

John D Reynolds ◽

Andrew W Bateman

Keyword(s):

Climate Change ◽

High Temperature ◽

Current System ◽

Control Policy ◽

Sea Lice ◽

Future Climate Change ◽

Parasite Control ◽

Management Scenarios ◽

Farmed Fish ◽

Wild Salmon

Abstract The ectoparasitic copepods, sea lice (Lepeophtheirus salmonis and Caligus spp.), are major pests to salmon aquaculture and can also affect the health and survival of wild salmon. Policies exist to protect wild salmon by delousing farmed fish when louse abundance exceeds a threshold, but their effectiveness under future climate change is uncertain. We fitted a Bayesian model for sea-louse population dynamics and management to timeseries data of sea lice on farmed salmon in Pacific Canada and analysed the model under scenarios of warmer climates. We found that in high-temperature years, current parasite control policy becomes ineffective as sea-louse abundance is expected to increase. We simulated two alternative management scenarios and observed that both would decrease average louse counts on farms in high-temperature years relative to the current system but relied on more delousing treatments than are currently performed. We also found evidence that non-salmonids can play a role in louse transmission to farms, as increased farm colonization of Caligus clemensi occurs in April, coincident with wild herring (Clupea pallasii) spawner abundance. Our results highlight the need for careful management of sea lice on salmon farms in warmer years and the importance of policies designed to account for future environmental change.

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The effect of sea lice (Lepeophtheirus salmonis) on juvenile pink salmon (Oncorhynchus gorbuscha) swimming endurance

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f10-121 ◽

2010 ◽

Vol 67 (12) ◽

pp. 2045-2051 ◽

Cited By ~ 10

Author(s):

Paul A. Mages ◽

Lawrence M. Dill

Keyword(s):

Pink Salmon ◽

Sea Lice ◽

Oncorhynchus Gorbuscha ◽

Control Fish ◽

Lepeophtheirus Salmonis ◽

Pink Salmon Oncorhynchus Gorbuscha ◽

Swim Performance ◽

Ecological Implications ◽

Seaward Migration ◽

Swimming Endurance

The swimming endurance of naturally and experimentally infected juvenile pink salmon ( Oncorhynchus gorbuscha ) was measured to determine the effects of sea lice ( Lepeophtheirus salmonis ). Salmon naturally infected with adult male and preadult stage lice did not appear to have a reduced swim performance, but when experimentally infected with adult female lice, juvenile salmon showed a reduced ability to swim compared with uninfected control fish, and this effect increased with lice load. A reduced swimming endurance is not only likely to influence predation risk for salmon, but may have other ecological implications, such as slower seaward migration.

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Sea lice infection of juvenile pink salmon (Oncorhynchus gorbuscha): effects on swimming performance and postexercise ion balance

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f10-150 ◽

2011 ◽

Vol 68 (2) ◽

pp. 241-249 ◽

Cited By ~ 21

Author(s):

L. Nendick ◽

M. Sackville ◽

S. Tang ◽

C. J. Brauner ◽

A. P. Farrell

Keyword(s):

Swimming Performance ◽

Life Stage ◽

Pink Salmon ◽

Infection Intensity ◽

Sea Lice ◽

Whole Body ◽

Oncorhynchus Gorbuscha ◽

Swimming Velocity ◽

Pink Salmon Oncorhynchus Gorbuscha ◽

Average Body Mass

Sea lice ( Lepeophtheirus salmonis ) infection negatively affected swimming performance and postswim body ion concentrations of juvenile pink salmon ( Oncorhynchus gorbuscha ) at a 0.34 g average body mass but not at 1.1 g. Maximum swimming velocity (Umax) was measured on over 350 individual pink salmon (0.2–3.0 g), two-thirds of which had a sea lice infection varying in intensity (one to three sea lice per fish) and life stage (chalimus 1 to preadult). For fish averaging 0.34 g (caught in a nearby river free of sea lice and transferred to seawater before being experimentally infected), the significant reduction in Umax was dependent on sea lice life stage, not intensity, and Umax decreased only after the chalimus 2 life stage. Experimental infections also significantly elevated postswim whole body concentrations of sodium (by 23%–28%) and chloride (by 22%–32%), but independent of sea lice developmental stage or infection intensity. For fish averaging 1.1 g (captured in seawater with existing sea lice), the presence of sea lice had no significant effect on either Umax or postswim whole body ions. Thus, a single L. salmonis impacted swimming performance and postswim whole body ions of only the smallest pink salmon and with a sea louse stage of chalimus 3 or greater.

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