OOS 28-10 - Aquaculture-induced changes to dynamics of a migratory host and specialist parasite: a case study of pink salmon and sea lice

Wednesday, August 10, 2011: 4:40 PM
17B, Austin Convention Center
Jaime Ashander, Center for Population Biology, University of California, Davis, Davis, CA, Martin Krkosek, Department of Zoology, University of Otago, New Zealand and Mark, A. Lewis, Mathematical & Statistical Sciences, University of Alberta, Edmonton, AB, Canada

Exchange of diseases between domesticated and wild animals is a rising  concern for conservation. In the ocean, many species display life  histories that separate juveniles from adults. For pink salmon (Oncorhynchus gorbuscha) and parasitic sea lice (Lepeophtheirus salmonis) infection of juvenile salmon in early marine life occurs near salmon sea-cage aquaculture sites and is associated with declining abundance of wild salmon. Here, we develop a theoretical model for the pink salmon/sea lice host-parasite system and use it to explore the effects of aquaculture hosts, acting as reservoirs, on dynamics. Because pink salmon have a two-year lifespan, even- and  odd-year lineages breed  in alternate years in a given river. These lineages can have consistently different relative abundances, a  phenomenon termed "line dominance."  These dominance relationships between host lineages serve as a useful probe for the dynamical effects of introducing aquaculture hosts into this host-parasite system.


We demonstrate how parasite spill-over (farm-to-wild transfer) and spill-back (wild-to-farm transfer) with aquaculture hosts can either increase or decrease the line  dominance in an affected wild population. The direction of the effect depends on the response of farms to  wild-origin infection. If aquaculture parasites are managed to a constant abundance, independent of the intensity of infections from wild to farm, then line dominance increases. On the other hand, if wild-origin parasites on aquaculture hosts are controlled proportional to their abundance then line dominance decreases.

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