TP10 Migrations: Role of Biota in Contaminant Distribution
D135-136
1:20 PM - 4:40 PM, Tuesday
() Sockeye salmon as vectors of nutrients and contaminants in nursery lakes: a food web study.
Gregory-Eaves, I1, Kimpe, L1, MacDonald, R2, Finney, B3, Blais, J, 1 Dept. of Biology, University of Ottawa, Ottawa, Ontario, Canada2 Institute of Ocean Sciences, Sydney, BC, Canada3 Institute of Marine Science, Fairbanks, Alaska, Canada
ABSTRACT- Over the past decade, numerous studies have demonstrated that Pacific salmon are important vectors of nutrients into freshwater ecosystems. The annual post-spawning die-off of thousands to millions of fish, who are returning to freshwaters after having done most of their growing in the North Pacific, results in a large release of nutrients. This influx of nutrients can be critical in the development of the juvenile salmon that rear in freshwaters for several years before migrating to the ocean. Recent research by our group and others, however, has revealed that the return of mature sockeye salmon also results in the delivery of persistent organic pollutants. The magnitude to which these compounds are being biomagnified in juvenile salmon as well as other fish residing in sockeye nursery lakes is the focus of this study. In particular, we are looking at fish from lakes along a large salmon return gradient (0 – 30,000 spawners/km2). We have conducted gut content analyses and stable isotope analyses to understand the pathways though which salmon-derived nutrients and contaminants might be bioaccumulated: direct consumption of salmon tissues or via an indirect food web pathway. Stable isotope analyses and otolith microchemistry are also being applied to determine whether some of our non-salmon fish are actually anadromous themselves. To date, our stable isotope analyses have revealed that most our non-salmon fish have elevated 
15N signatures relative to sockeye salmon, suggesting that they occupy a higher trophic position. Many of these non-salmon fish also have a higher proportion of biomagnifying PCBs than salmon, which would support the hypothesis that salmon are an important source of contaminants. Overall, the levels of PCBs detected are low, but could have sub-lethal impacts on large consumers.
Key words: vector, salmon, polychlorinated biphenyl, trophic