Oust the louse: leaping behaviour removes sea lice from wild juvenile sockeye salmon <scp><i>Oncorhynchus nerka</i></scp>

Atkinson, Emma M.; Bateman, Andrew; Dill, Lawrence M.; Krkošek, Martin; Reynolds, John D.; Godwin, Sean C.

doi:10.1111/jfb.13684

Cited by 13 publications

(11 citation statements)

References 72 publications

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“…Although, it should be noted that jumps may also be performed in response other drivers, such as salmon lice infestations (Samsing et al. 2015; Atkinson et al. 2018).…”

Section: Discussionmentioning

confidence: 99%

Differential effects of internal tagging depending on depth treatment in Atlantic salmon: a cautionary tale for aquatic animal tag use

et al. 2018

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Electronic tags are widespread tools for studying aquatic animal behavior; however, tags risk behavioral manipulation and negative welfare outcomes. During an experiment to test behavioral differences of Atlantic salmon Salmo salar in different aquaculture cage types, including ones expected to elicit deeper swimming behavior, we found negative tagging effects depending on whether cages were depth-modified. In the experiment, data storage tags implanted in Atlantic salmon tracked their depth behavior and survival in unmodified sea-cages and depth-modified sea-cages that forced fish below or into a narrow seawater- or freshwater-filled snorkel tube from a 4 m net roof to the surface. All tagged individuals survived in unmodified cages; however, survival was reduced to 62% in depth-modified cages. Survivors in depth-modified cages spent considerably less time above 4 m than those in unmodified cages, and dying individuals in depth-modified cages tended to position in progressively shallower water. The maximum depth that fish in our study could attain neutral buoyancy was estimated at 22 m in seawater. We calculated that the added tag weight in water reduced this to 8 m, and subtracting the tag volume from the peritoneal cavity where the swim bladder reinflates reduced this further to 4 m. We conclude that the internal tag weight and volume affected buoyancy regulation as well as the survival and behavior of tagged fish. Future tagging studies on aquatic animals should carefully consider the buoyancy-related consequences of internal tags with excess weight in water, and the inclusion of data from dying tagged animals when estimating normal depth behaviors.

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“…Although, it should be noted that jumps may also be performed in response other drivers, such as salmon lice infestations (Samsing et al. 2015; Atkinson et al. 2018).…”

Section: Discussionmentioning

confidence: 99%

Differential effects of internal tagging depending on depth treatment in Atlantic salmon: a cautionary tale for aquatic animal tag use

et al. 2018

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“…In the case of sea lice, the counting protocol itself could be improved, for example by discontinuing the use of dip nets to avoid dislodging lice (Godwin et al 2015). The current protocol requires high diligence to minimize or retrieve dislodged sea lice; this is especially true for the highly mobile C. clemensi (Saksida et al 2015, Atkinson et al 2018, which could explain why our results indicated that C. clemensi are more underestimated than L. salmonis.…”

Section: Figmentioning

confidence: 90%

“…Similar to Jansen et al (2012), we model monthly louse counts per 10 fish (i.e., we multiplied the mean monthly counts by 10) and assume a negative binomial error distribution:

N_{L, t, f} \sim negative binomial ({normalμ}_{L, t, f}, {normalρ}_{normalL})

where N L, t , f is the reported mean motile louse count per 10 fish in month t on farm f , µ L, t , f is the predicted mean motile louse count per 10 fish for that month and farm, and ρ L is the negative binomial shape parameter, fit as an additional free parameter. We allowed the shape parameter of the negative binomial to vary between species because one key relationship that drives overdispersion is the ratio of immigrants to births (Bolker 2008); the relative contributions of colonization and on‐farm population growth to counts are likely to be very different between C. clemensi and L. salmonis due to the large difference in their mobility among hosts (Saksida et al 2015, Atkinson et al 2018). Using the negative binomial prevents complications associated with zero counts because, unlike the gamma distribution, the negative binomial distribution allows for zeros.…”

Section: Methodsmentioning

confidence: 99%

Bias in self‐reported parasite data from the salmon farming industry

Godwin

Krkošek

Reynolds

et al. 2020

Ecological Applications

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Many industries are required to monitor themselves in meeting regulatory policies intended to protect the environment. Self-reporting of environmental performance can place the cost of monitoring on companies rather than taxpayers, but there are obvious risks of bias, often addressed through external audits or inspections. Surprisingly, there have been relatively few empirical analyses of bias in industry self-reported data. Here, we test for bias in reporting of environmental compliance data using a unique data set from Canadian salmon farms, where companies monitor the number of parasitic sea lice on fish in open sea pens, in order to minimize impacts on wild fish in surrounding waters. We fit a hierarchical populationdynamics model to these sea-louse count data using a Bayesian approach. We found that the industry's monthly counts of two sea-louse species, Caligus clemensi and Lepeophtheirus salmonis, increased by a factor of 1.95 (95% credible interval: 1.57, 2.42) and 1.18 (1.06, 1.31), respectively, in months when counts were audited by the federal fisheries department. Consequently, industry sea-louse counts are less likely to trigger costly but mandated delousing treatments intended to avoid sea-louse epidemics in wild juvenile salmon. These results highlight the potential for combining external audits of industry self-reported data with analyses of their reporting to maintain compliance with regulations, achieve intended conservation goals, and build public confidence in the process.

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“…Atlantic and pink (Oncorhynchus gorbuscha) salmon increase their leaping and rolling activity when exposed to louse copepodids (Grimnes & Jakobsen 1996;Webster et al 2007), and this behaviour can reduce new infestations by up to 31% (Bui et al 2018c). Motile lice are also removed in this way by sockeye salmon (O. nerka; Atkinson et al 2018). As salmonids evolved new 'mechanical delousing' behaviours, lice may in turn have evolved improved attachment ability.…”

Section: Selection For Improved Attachmentmentioning

confidence: 99%

Evolution of salmon lice in response to management strategies: a review

Coates

Phillips

Bui

et al. 2021

Reviews in Aquaculture

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Ectoparasitic salmon lice (Lepeophtheirus salmonis) present a major challenge to Atlantic salmon (Salmo salar) aquaculture. The demand for effective louse control has produced diverse management strategies. These strategies essentially impose novel selection pressures on parasite populations, driving the evolution of resistance. Here we assess the potential for salmon lice to adapt to current prevention and control methods. Lice have evolved resistance to at least four of five chemical therapeutants, and use of these chemicals has declined significantly in recent years. The industry has shifted to alternative non-chemical approaches, yet lice may adapt to these as well. Early research suggests that phenotypic variation exists in the louse population upon which non-chemical selection pressures could act and that this variation may have a genetic basis. From the existing evidence, as well as an examination of evolutionary processes in other relevant parasite and pest systems, we conclude that the evolution of non-chemical resistance is an emergent concern that must be considered by the industry. We recommend areas for focused research to better assess this risk. It is also important to determine whether phenotypic shifts in response to non-chemical selection may shift the ecological niche of the parasite, as this may have cascading effects on wild salmon populations. We also recommend further research to identify strategy combinations that have antagonistic selective effects that slow louse evolution and those with synergistic effects that should be avoided. Greater understanding of evolutionary processes can inform aquaculture policies that counteract the rise of resistant parasite populations.

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Oust the louse: leaping behaviour removes sea lice from wild juvenile sockeye salmon Oncorhynchus nerka

Cited by 13 publications

References 72 publications

Differential effects of internal tagging depending on depth treatment in Atlantic salmon: a cautionary tale for aquatic animal tag use

Differential effects of internal tagging depending on depth treatment in Atlantic salmon: a cautionary tale for aquatic animal tag use

Bias in self‐reported parasite data from the salmon farming industry

Evolution of salmon lice in response to management strategies: a review

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