Perspectives on Pink Salmon and Sea Lice: Scientific Evidence Fails to Support the Extinction Hypothesis

2008 ◽  
Vol 16 (4) ◽  
pp. 403-412 ◽  
Author(s):  
KENNETH M. BROOKS ◽  
SIMON R. M. JONES
Keyword(s):  
Scientific Evidence ◽  
Pink Salmon ◽  
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.

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

2011 ◽  
Vol 68 (2) ◽  
pp. 241-249 ◽  
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.

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.

Growth and ionoregulatory ontogeny of wild and hatchery-raised juvenile pink salmon (Oncorhynchus gorbuscha)

2009 ◽  
Vol 87 (3) ◽  
pp. 221-228 ◽  
Author(s):  
A. Grant ◽  
M. Gardner ◽  
L. Nendick ◽  
M. Sackville ◽  
A. P. Farrell ◽  
...  
Keyword(s):  
Specific Growth ◽  
Pink Salmon ◽  
Sea Lice ◽  
Whole Body ◽  
Oncorhynchus Gorbuscha ◽  
Life History Stage ◽  
Initial Exposure ◽  
Pink Salmon Oncorhynchus Gorbuscha ◽  
Future Studies ◽  
Specific Growth Rates

Juvenile pink salmon ( Oncorhynchus gorbuscha (Walbaum, 1792)) enter seawater (SW) shortly following emergence. Little is known about growth and development during this life-history stage when sensitivity to sea louse exposure may be high, an issue that is of current concern in British Columbia. We tested the hypothesis that growth and ionoregulatory development were similar in hatchery-raised (Quinsam) and wild (Glendale and One’s Point) juvenile pink salmon (measured over 22 weeks) following SW entry. Fish body mass increased from 0.20 ± 0.01 to 6.47 ± 0.37 g, with mean specific growth rates of 2.74% to 3.05% body mass·day–1 among the three groups. In all three groups, gill Na+–K+-ATPase (NKA) activity peaked at 12 µmol ADP·mg protein–1·h–1 following 8 weeks post-transfer to SW. Whole body Na+ and Cl– concentrations, which again did not differ among groups, were highest upon initial exposure to SW (~70 mmol·kg wet mass–1) and declined over time as gill NKA activity increased, indicating that the hypo-osmoregulatory capacity was not fully developed following emergence and initial entry into SW. Thus, consistent with our hypothesis, few differences were observed between hatchery-raised and wild juvenile pink salmon reared under laboratory conditions. These baseline data may be important for future studies in determining the effects of sea lice on wild juvenile pink salmon.

scholarly journals Can reduced predation offset negative effects of sea louse parasites on chum salmon?

2014 ◽  
Vol 281 (1776) ◽  
pp. 20132913 ◽  
Author(s):  
Stephanie J. Peacock ◽  
Brendan M. Connors ◽  
Martin Krkošek ◽  
James R. Irvine ◽  
Mark A. Lewis
Keyword(s):  
Statistical Power ◽  
Chum Salmon ◽  
Pink Salmon ◽  
Sea Lice ◽  
Unexpected Result ◽  
Negative Effects ◽  
Farmed Salmon ◽  
Host Parasite ◽  
The Impact ◽  
High Statistical Power

The impact of parasites on hosts is invariably negative when considered in isolation, but may be complex and unexpected in nature. For example, if parasites make hosts less desirable to predators then gains from reduced predation may offset direct costs of being parasitized. We explore these ideas in the context of sea louse infestations on salmon. In Pacific Canada, sea lice can spread from farmed salmon to migrating juvenile wild salmon. Low numbers of sea lice can cause mortality of juvenile pink and chum salmon. For pink salmon, this has resulted in reduced productivity of river populations exposed to salmon farming. However, for chum salmon, we did not find an effect of sea louse infestations on productivity, despite high statistical power. Motivated by this unexpected result, we used a mathematical model to show how a parasite-induced shift in predation pressure from chum salmon to pink salmon could offset negative direct impacts of sea lice on chum salmon. This shift in predation is proposed to occur because predators show an innate preference for pink salmon prey. This preference may be more easily expressed when sea lice compromise juvenile salmon hosts, making them easier to catch. Our results indicate how the ecological context of host–parasite interactions may dampen, or even reverse, the expected impact of parasites on host 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.

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.

The impact of sea lice on the physiology of wild out-migrating juvenile pink salmon

2009 ◽  
Vol 153 (2) ◽  
pp. S141
Author(s):  
Colin J. Brauner ◽  
Michael Sackville ◽  
Laura Nendick ◽  
Steve Tang ◽  
Manuela Gardner ◽  
...  
Keyword(s):  
Pink Salmon ◽  
Sea Lice ◽  
The Impact

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.

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