Polychlorinated biphenyl and polybrominated diphenyl ether profiles vary with feeding ecology and marine rearing distribution among 10 Chinook salmon (Oncorhynchus tshawytscha) stocks in the North Pacific Ocean.

Chinook salmon (Oncorhynchus tshawytscha) along the west coast of North America have experienced significant declines in abundance and body size over recent decades due to several anthropogenic stressors. Understanding the reasons underlying the relatively high levels of persistent organic pollutants (POPs) in Chinook stocks is an important need, as it informs recovery planning for this foundation species, as well for the Chinook-dependent Resident killer whales (Orcinus orca, RKW) of British Columbia (Canada) and Washington State (USA). We evaluated the influence of stock-related differences in feeding ecology, using stable isotopes, and marine rearing ground on the concentrations and patterns of polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) in Chinook salmon. A principal components analysis (PCA) revealed a clear divergence of PCB and PBDE congener patterns between Chinook with a nearshore rearing distribution ('shelf resident') versus a more offshore distribution. Shelf resident Chinook had 12-fold higher PCB concentrations and 46-fold higher PBDE concentrations relative to offshore stocks. Shelf resident Chinook had PCB and PBDE profiles that were heavier and dominated by more bioaccumulative congeners, respectively. The higher δ

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Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.