Proceedings of the Royal Society B: Biological Sciences
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Transmission dynamics of parasitic sea lice from farm to wild salmon

Martin Krkošek

Martin Krkošek

Department of Mathematical and Statistical Sciences, Center for Mathematical Biology, University of AlbertaEdmonton, AlbertaCanada T6G 2E7

Department of Biological Sciences, University of AlbertaEdmonton, AlbertaCanada T6G 2E7

[email protected]

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Mark A Lewis

Mark A Lewis

Department of Mathematical and Statistical Sciences, Center for Mathematical Biology, University of AlbertaEdmonton, AlbertaCanada T6G 2E7

Department of Biological Sciences, University of AlbertaEdmonton, AlbertaCanada T6G 2E7

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John P Volpe

John P Volpe

Department of Biological Sciences, University of AlbertaEdmonton, AlbertaCanada T6G 2E7

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    Marine salmon farming has been correlated with parasitic sea lice infestations and concurrent declines of wild salmonids. Here, we report a quantitative analysis of how a single salmon farm altered the natural transmission dynamics of sea lice to juvenile Pacific salmon. We studied infections of sea lice (Lepeophtheirus salmonis and Caligus clemensi ) on juvenile pink salmon (Oncorhynchus gorbuscha) and chum salmon (Oncorhynchus keta) as they passed an isolated salmon farm during their seaward migration down two long and narrow corridors. Our calculations suggest the infection pressure imposed by the farm was four orders of magnitude greater than ambient levels, resulting in a maximum infection pressure near the farm that was 73 times greater than ambient levels and exceeded ambient levels for 30 km along the two wild salmon migration corridors. The farm-produced cohort of lice parasitizing the wild juvenile hosts reached reproductive maturity and produced a second generation of lice that re-infected the juvenile salmon. This raises the infection pressure from the farm by an additional order of magnitude, with a composite infection pressure that exceeds ambient levels for 75 km of the two migration routes. Amplified sea lice infestations due to salmon farms are a potential limiting factor to wild salmonid conservation.

    Footnotes

    †Present address: School of Environmental Studies, University of Victoria, Victoria, BC, Canada V8W 2Y2.

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