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

Science ◽  
2008 ◽  
Vol 322 (5909) ◽  
pp. 1790.3-1790 ◽  
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.

scholarly journals Physiological consequences of the salmon louse ( Lepeophtheirus salmonis ) on juvenile pink salmon ( Oncorhynchus gorbuscha ): implications for wild salmon ecology and management, and for salmon aquaculture

2012 ◽  
Vol 367 (1596) ◽  
pp. 1770-1779 ◽  
Author(s):  
C. J. Brauner ◽  
M. Sackville ◽  
Z. Gallagher ◽  
S. Tang ◽  
L. Nendick ◽  
...  
Keyword(s):  
British Columbia ◽  
Ecosystem Health ◽  
Pink Salmon ◽  
Oncorhynchus Gorbuscha ◽  
Lepeophtheirus Salmonis ◽  
Pink Salmon Oncorhynchus Gorbuscha ◽  
Salmon Louse ◽  
Wild Salmon ◽  
Salmon Aquaculture ◽  
The Impact

Pink salmon, Oncorhynchus gorbuscha , are the most abundant wild salmon species and are thought of as an indicator of ecosystem health. The salmon louse, Lepeophtheirus salmonis , is endemic to pink salmon habitat but these ectoparasites have been implicated in reducing local pink salmon populations in the Broughton Archipelago, British Columbia. This allegation arose largely because juvenile pink salmon migrate past commercial open net salmon farms, which are known to incubate the salmon louse. Juvenile pink salmon are thought to be especially sensitive to this ectoparasite because they enter the sea at such a small size (approx. 0.2 g). Here, we describe how ‘no effect’ thresholds for salmon louse sublethal impacts on juvenile pink salmon were determined using physiological principles. These data were accepted by environmental managers and are being used to minimize the impact of salmon aquaculture on wild pink salmon populations.

Sea lice (Lepeophtheirus salmonis) infestations and the productivity of pink salmon (Oncorhynchus gorbuscha) in the Broughton Archipelago, British Columbia, Canada

2011 ◽  
Vol 68 (1) ◽  
pp. 17-29 ◽  
Author(s):  
Martin Krkošek ◽  
Ray Hilborn
Keyword(s):  
British Columbia ◽  
Large Scale ◽  
Spatial Scales ◽  
Population Decline ◽  
Pink Salmon ◽  
Sea Lice ◽  
Oncorhynchus Gorbuscha ◽  
Lepeophtheirus Salmonis ◽  
Pink Salmon Oncorhynchus Gorbuscha ◽  
Lice Infestations

The spread of salmon lice ( Lepeophtheirus salmonis ) from salmon farms may threaten some wild salmon populations. Infestations of wild juvenile pink salmon ( Oncorhynchus gorbuscha ) have been associated with high mortality and population decline. Using stock–recruit data for pink salmon from the central coast of British Columbia, we analyzed how fishing mortality and spatial covariation combine with louse infestation to affect pink salmon population dynamics. The results indicate substantial coherence in survival at nested spatial scales — large-scale regional covariation and smaller scale covariation within management areas. Populations exposed to salmon farms (those from the Broughton Archipelago) show a sharp decline in productivity during sea lice infestations relative to pre-infestation years. Unexposed populations (comprising four management areas) did not experience a change in productivity during infestation years and had similar productivity to exposed populations before infestations. Our results suggest that sea lice infestations may result in declines of pink salmon populations and that management and policy of salmon farms should consider protecting wild juvenile salmon from exposure to sea lice.

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

2010 ◽  
Vol 67 (12) ◽  
pp. 2045-2051 ◽  
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.

scholarly journals Response of the Sea Louse Lepeophtheirus salmonis Infestation Levels on Juvenile Wild Pink, Oncorhynchus gorbuscha, and Chum, O. keta, Salmon to Arrival of Parasitized Wild Adult Pink Salmon

2006 ◽  
Vol 120 (2) ◽  
pp. 199
Author(s):  
Alexandra Morton ◽  
Rob Williams
Keyword(s):  
Chum Salmon ◽  
Pacific Salmon ◽  
Pink Salmon ◽  
Primary Source ◽  
Sea Lice ◽  
Oncorhynchus Gorbuscha ◽  
Oncorhynchus Keta ◽  
Lepeophtheirus Salmonis ◽  
Louse Infestation ◽  
Age Cohorts

Recent recurring infestations of Sea Lice, Lepeophtheirus salmonis, on juvenile Pacific salmon (Oncorhynchus spp.) and subsequent annual declines of these stocks have made it imperative to identify the source of Sea Lice. While several studies now identify farm salmon populations as sources of Sea Louse larvae, it is unclear to what extent wild salmonid hosts also contribute Sea Lice. We measured Sea Louse numbers on adult Pink Salmon (Oncorhynchus gorbuscha) migrating inshore. We also measured Sea Louse numbers on wild juvenile Pink and Chum salmon (Oncorhynchus keta) migrating to sea before the adults returned, and as the two age cohorts mingled. Adult Pink Salmon carried an average of 9.89 (SE 0.90) gravid lice per fish, and thus were capable of infecting the adjacent juveniles. Salinity and temperature remained favourable to Sea Louse reproduction throughout the study. However, all accepted measures of Sea Louse infestation failed to show significant increase on the juvenile salmon, either in overall abundance of Sea Lice or of the initial infective-stage juvenile lice, while the adult wild salmon were present in the study area. This study suggests that even during periods of peak interaction, wild adult salmon are not the primary source of the recent and unprecedented infestations of Sea Lice on juvenile Pacific Pink and Chum salmon in the inshore waters of British Columbia.

scholarly journals Differential infestation of juvenile Pacific salmon by parasitic sea lice in British Columbia, Canada

2020 ◽  
Vol 77 (12) ◽  
pp. 1960-1968
Author(s):  
Cole B. Brookson ◽  
Martin Krkošek ◽  
Brian P.V. Hunt ◽  
Brett T. Johnson ◽  
Luke A. Rogers ◽  
...  
Keyword(s):  
British Columbia ◽  
Pacific Salmon ◽  
Pink Salmon ◽  
Host Specialization ◽  
Sea Lice ◽  
Oncorhynchus Keta ◽  
Lepeophtheirus Salmonis ◽  
Fraser River ◽  
Farmed Salmon ◽  
Louse Species

Fraser River Pacific salmon have declined in recent decades, possibly from parasitism by sea lice (Caligus clemensi and Lepeophtheirus salmonis). We describe the abundance of both louse species infesting co-migrating juvenile pink (Oncorhynchus gorbuscha), chum (Oncorhynchus keta), and sockeye (Oncorhynchus nerka) salmon over 5 years in the Discovery Islands and Johnstone Strait, British Columbia. The generalist louse, C. clemensi, was 5, 7, and 39 times more abundant than the salmonid specialist, L. salmonis, on pink, chum, and sockeye salmon, respectively. Caligus clemensi abundance was higher on pink salmon (0.45, 95% CI: 0.38–0.55) and sockeye (0.39, 95% CI: 0.33–0.47) than on chum salmon. Lepeophtheirus salmonis abundance was highest on pink salmon (0.09, 95% CI = 0.06–0.15). Caligus clemensi had higher abundances in Johnstone Strait than in the Discovery Islands. These results suggest differences in host specialization and transmission dynamics between louse species. Because both lice infest farmed salmon, but only C. clemensi infests Pacific herring (Clupea pallasii), conservation science and management regarding lice and Fraser River salmon should further consider C. clemensi and transmission from farmed salmon and wild herring.

scholarly journals First Report of a Sea Louse, Lepeophtheirus salmonis, Infestation on Juvenile Pink Salmon, Oncorhynchus gorbuscha, in Nearshore Habitat

2003 ◽  
Vol 117 (4) ◽  
pp. 634 ◽  
Author(s):  
Alexandra B. Morton ◽  
Rob Williams
Keyword(s):  
Salmo Trutta ◽  
Pink Salmon ◽  
Sea Lice ◽  
Oncorhynchus Gorbuscha ◽  
Lepeophtheirus Salmonis ◽  
Pink Salmon Oncorhynchus Gorbuscha ◽  
Sea Trout ◽  
Close Proximity ◽  
Lethal Limit ◽  
Nearshore Habitat

High infestation rates of the Sea Louse (Lepeophtheirus salmonis) have been reported on juvenile salmonids in Europe since 1989; however, this species has not been reported on juvenile Pacific salmonids until now. Magnitude of Sea Lice infestation was examined in 2001 on juvenile Pink Salmon (Oncorhynchus gorbuscha) migrating through a British Columbia archipelago. On average, the 751 juvenile Pink Salmon sampled weighed 2.25 g (± 0.039 SE), were infected with 11.3 (± 0.41 SE) Sea Lice per fish and 6.1 (± 0.24SE) Sea Lice per gram host weight. Fully 75.0% of fish were infected at loads equivalent to or higher than the lethal limit reported for much larger Sea Trout (Salmo trutta) post-smolts. Abundance (Kruskal-Wallis statistic = 100.95, p<0.0001) and intensity (KW= 70.05, p<0.0001) of lice, and mean number of lice/g host weight (K-W= 112.23, p<0.0001) were significantly higher in juvenile Pink Salmon in close proximity to salmon farms, than in Pink Salmon distant from salmon farms.

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

2010 ◽  
Vol 67 (12) ◽  
pp. 1925-1932 ◽  
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.

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

Science ◽  
2008 ◽  
Vol 322 (5909) ◽  
pp. 1790.2-1790 ◽  
Author(s):  
Brian E. Riddell ◽  
Richard J. Beamish ◽  
Laura J. Richards ◽  
John R. Candy
Keyword(s):  
Pink Salmon ◽  
Local Extinction ◽  
Sea Lice ◽  
Wild Salmon ◽  
Salmon Farming ◽  
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.

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

2016 ◽  
Vol 73 (8) ◽  
pp. 1164-1172 ◽  
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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