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T4 PM Endangered Species and Environmental Contaminants: Status of the Science (Part 2)
(YLI-1117-745045) Pacific salmon as potential sources of persistent organic pollutants (POPs) in southern resident killer whales.
Ylitalo, Gina1, O'Neill, Sandra2, Brown, Donald1, West, James2, Sloan, Catherine1, Bolton, Jennie1, Krahn, Margaret1, 1 NOAA Fisheries, Northwest Fisheries Science Center, ECD, Seattle, WA, United States2 Washington Deparment of Fish and Wildlife, Puget Sound Ambient Monitoring Program, Olympia, WA, United States
ABSTRACT- From 1996 to 2001, the southern resident killer whale (Orcinus orca) population residing in Puget Sound/Georgia Basin declined 20%. Due to this decline, NOAA Fisheries has recently proposed to list the southern resident population as threatened under the U.S. Endangered Species Act. Potential factors contributing to the population decline include reduced prey quality/quantity, exposure to high levels of toxic, persistent organic pollutants (POPs) and noise and disturbance from vessel traffic. Studies to date have shown that southern residents contain higher concentrations of POPs than northern resident killer whales. Elevated contaminant levels may be due to dietary differences between these two whale populations or to regional differences in POP concentrations in their prey. A dietary study indicated that, during the summer months, the primary prey of northern and southern resident whales are salmon, particularly Chinook salmon. To determine if there were regional differences in POP concentrations in known summer prey of northern and southern resident whales, we sampled free-ranging salmon from summer feeding areas of southern and northern resident killer whales. We found significantly higher levels of PCBs and polybrominated diphenyl ethers (PBDEs) in whole bodies of Chinook and coho returning to Puget Sound than those measured in other Pacific coast salmon populations. Concentrations of PCBs and PBDEs in Puget Sound Chinook populations were 3-5 times higher than those measured in Chinook from other locations. Similarly, concentrations of these compounds were 3-5 times higher in southern residents than those in northern resident killer whales. Examination of ratios of contaminants in southern residents and their potential prey showed that the whales are more likely feeding on salmon than other prey fish species from the Puget Sound region. From these data, it appears that Chinook salmon, especially Puget Sound populations, are the likely sources of POPs to southern resident killer whales.
Key words: killer whales, POPs, salmon
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