Proceedings of the Royal Society B: Biological Sciences
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Effects of host migration, diversity and aquaculture on sea lice threats to Pacific salmon populations

Martin Krkošek

Martin Krkošek

Centre for Mathematical Biology, Departments of Mathematical and Statistical Sciences and Biological Sciences, University of AlbertaEdmonton, Alberta, Canada T6G 2G1

[email protected]

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,
Allen Gottesfeld

Allen Gottesfeld

Skeena Fisheries CommissionHazelton, British Columbia, Canada V0J 1Y0

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,
Bart Proctor

Bart Proctor

Oona River Resources AssociationOona River, British Columbia, Canada V0V 1E0

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,
Dave Rolston

Dave Rolston

Oona River Resources AssociationOona River, British Columbia, Canada V0V 1E0

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,
Charmaine Carr-Harris

Charmaine Carr-Harris

Oona River Resources AssociationOona River, British Columbia, Canada V0V 1E0

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and
Mark A Lewis

Mark A Lewis

Centre for Mathematical Biology, Departments of Mathematical and Statistical Sciences and Biological Sciences, University of AlbertaEdmonton, Alberta, Canada T6G 2G1

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    Animal migrations can affect disease dynamics. One consequence of migration common to marine fish and invertebrates is migratory allopatry—a period of spatial separation between adult and juvenile hosts, which is caused by host migration and which prevents parasite transmission from adult to juvenile hosts. We studied this characteristic for sea lice (Lepeophtheirus salmonis and Caligus clemensi) and pink salmon (Oncorhynchus gorbuscha) from one of the Canada's largest salmon stocks. Migratory allopatry protects juvenile salmon from L. salmonis for two to three months of early marine life (2–3% prevalence). In contrast, host diversity facilitates access for C. clemensi to juvenile salmon (8–20% prevalence) but infections appear ephemeral. Aquaculture can augment host abundance and diversity and increase parasite exposure of wild juvenile fish. An empirically parametrized model shows high sensitivity of salmon populations to increased L. salmonis exposure, predicting population collapse at one to five motile L. salmonis per juvenile pink salmon. These results characterize parasite threats of salmon aquaculture to wild salmon populations and show how host migration and diversity are important factors affecting parasite transmission in the oceans.

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