PCB congeners in Lake Michigan coho (Oncorhynchus kisutch) and Chinook (Oncorhynchus tshawytscha) salmon

We determined PCB congener concentrations in coho and chinook salmon collec ted in two Lake Michigan tributaries during the fall of 1996. Chinook salmo n were larger than coho salmon and contained higher concentrations of the 7 8 PCB congeners we detected. There were no differences between male and fem ale chinook or coho salmon in size or their PCB concentrations. Among indiv idual fish, we found little evidence for a relationship between congener co ncentrations and percent lipid; however, congener concentrations did show a generally positive relationship with salmon size. Fish and macroinvertebra te congener concentrations are clearly related, and PCB congeners biomagnif y similar to 20-30-fold as they flow from macroinvertebtates, two trophic l evels below salmon, to the salmon. Slopes of regressions of salmonid congen er concentrations on macroinvertebrate congener concentrations within homol ogs indicated that the degree of biomagnification generally increased with the degree of congener chlorination, although this pattern was much stronge r for Mysis than for Diporeia. Log K-ow and categorical variables for copla nar and "toxic" PCBs were not significant additional model terms, indicatin g that bioaccumulation of PCB congeners was not statistically related to th ese physicochemical attributes of the PCBs. The distribution of homologue P CBs shifts from a distinct predominance of hexachlorobiphenyls in macroinve rtebrates to pentachlorobiphenyls and hexachlorobiphenyls in the salmon.