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.

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.

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.

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 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 Sea lice dispersion and salmon survival in relation to salmon farm activity in the Broughton Archipelago

2010 ◽  
Vol 68 (1) ◽  
pp. 144-156 ◽  
Author(s):  
Alexandra Morton ◽  
Rick Routledge ◽  
Amy McConnell ◽  
Martin Krkošek
Keyword(s):  
Pacific Salmon ◽  
Pink Salmon ◽  
Primary Source ◽  
Sea Lice ◽  
Oncorhynchus Gorbuscha ◽  
Oncorhynchus Keta ◽  
Juvenile Salmon ◽  
Migration Route ◽  
Migration Routes ◽  
Salmon Farm

Abstract Morton, A., Routledge, R., McConnell, A., and Krkošek, 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. 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, ∼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.

scholarly journals Marine growth patterns of southern British Columbia chum salmon explained by interactions between density-dependent competition and changing climate

2017 ◽  
Vol 74 (7) ◽  
pp. 1077-1087 ◽  
Author(s):  
Allan J. Debertin ◽  
James R. Irvine ◽  
Carrie A. Holt ◽  
Gladys Oka ◽  
Marc Trudel
Keyword(s):  
British Columbia ◽  
Chum Salmon ◽  
Pacific Salmon ◽  
Pink Salmon ◽  
Climate Variation ◽  
Growth Patterns ◽  
Oncorhynchus Gorbuscha ◽  
Oncorhynchus Keta ◽  
Density Dependent ◽  
Competition Effects

Thirty-nine years of scale growth measurements from Big Qualicum River chum salmon (Oncorhynchus keta) in southern British Columbia demonstrated that competition and climate variation affect marine growth and age-at-maturity. A longitudinal study design that accounted for correlation among individuals revealed growth at all ages was reduced when the biomass of North American chum, sockeye (Oncorhynchus nerka), and pink salmon (Oncorhynchus gorbuscha) was high. When North Pacific Gyre Oscillation (NPGO) was positive, indicating increased primary productivity, predicted growth increased. Climate variation influenced competition effects. For instance, density-dependent competition effects increased when NPGO became more positive and Pacific Decadal Oscillation became more negative (indicating cool conditions), causing the greatest range in predicted scale size. Chum salmon are likely to exhibit continued reduction in growth at age due to increased ocean temperatures driven by climate change and high aggregate salmon biomass that includes hatchery releases. If evidence of biomass and climate effects presented here are common among Pacific salmon populations, reduction of hatchery releases should be considered.

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.

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

2004 ◽  
Vol 61 (2) ◽  
pp. 147-157 ◽  
Author(s):  
Alexandra Morton ◽  
Richard Routledge ◽  
Corey Peet ◽  
Aleria Ladwig
Keyword(s):  
British Columbia ◽  
Chum Salmon ◽  
Wild Fish ◽  
Sea Lice ◽  
Oncorhynchus Gorbuscha ◽  
Oncorhynchus Keta ◽  
Lepeophtheirus Salmonis ◽  
Infection Rates ◽  
Fish Farms ◽  
Lethal Limit

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.

Supplementary Checks on the Scales of Pink Salmon (Oncorhynchus gorbuscha) and Chum Salmon (O. keta)

1965 ◽  
Vol 22 (6) ◽  
pp. 1477-1489 ◽  
Author(s):  
H. T. Bilton ◽  
W. E. Ricker
Keyword(s):  
British Columbia ◽  
Chum Salmon ◽  
Pink Salmon ◽  
Oncorhynchus Gorbuscha ◽  
Commercial Fisheries ◽  
Pink Salmon Oncorhynchus Gorbuscha ◽  
Clear Cut ◽  
Second Year Of Life ◽  
Second Year ◽  
Similar Incidence

Among 159 central British Columbia pink salmon that had been marked by removal of two fins as fry and had been recovered in commercial fisheries after one winter in the sea, the scales of about one-third showed a supplementary or "false" check near the centre of the scale, in addition to the single clear-cut annulus. This evidence from fish of known age confirms the prevailing opinion that such extra checks do not represent annuli, hence that the fish bearing them are in their second year of life rather than their third. Unmarked pink salmon from the same area, and some from southern British Columbia, had a generally similar incidence of supplementary checks. In both marked and unmarked fish the supplementary checks varied in distinctness from faint to quite clear. In a sample of scales of 14 double-fin marked chum salmon which were known to be in their 4th year, all fish had the expected 3 annuli, and 12 fish had a supplementary check inside the first annulus.

Orientation of Pink Salmon (Oncorhynchus gorbuscha) During Early Marine Migration from Bella Coola River System

1967 ◽  
Vol 24 (11) ◽  
pp. 2321-2338 ◽  
Author(s):  
M. C. Healey
Keyword(s):  
British Columbia ◽  
Pink Salmon ◽  
River System ◽  
Early Morning ◽  
Oncorhynchus Gorbuscha ◽  
Pink Salmon Oncorhynchus Gorbuscha ◽  
Salmon Fry ◽  
Marine Migration ◽  
Bella Coola

During May and June 1966, the migration of pink salmon fry from the Bella Coola River was studied in Burke Channel, British Columbia. The movement of pink fry down Burke Channel was saltatory. Short periods of active migration were interspersed with longer periods when the fry did not migrate and accumulated in bays. Fry were sampled from these accumulations and their ability to orient using celestial cues was examined. During the early morning, fry tended to prefer directions at right angles to their direction of migration, but at other times of the day preferred the direction of migration. The preference for the direction of migration was strongest at midday. Fry were better oriented on clear days than on cloudy days. These data indicate that fry may use celestial cues to find directions during their oceanic migrations.

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