Organochlorine concentration dynamics in Lake Michigan chinook salmon (Oncorhynchus tshawytscha)

To investigate how trophic level and physiological processes influence organochlorine (OC) chemical concentrations in chinook salmon (Oncorhynchus tshawytscha) and their offspring, data on polychlorinated biphenyl (PCB), and OC pesticides and metabolite concentrations in Lake Michigan chinook salmon muscle tissue, eggs, sac fry, and prey fish were analyzed. Total concentrations of PCBs in chinook salmon decreased exponentially from the mid-1970s to mid-1980s, but the concentrations have since shown an asymptotic response, a trend also seen in alewife (Alosa pseudoharengus), an exotic planktivore that is the principal prey of chinook salmon in western Lake Michigan, and bloater (Coregonus hoyi) an endemic planktivore. The total concentration of PCBs in chinook salmon were positively correlated with fish length. OC concentrations in chinook salmon eggs were positively correlated with the concentrations of these compounds in the muscle tissue of the gravid fish. Egg and sac fry OC concentrations were also positively correlated. Estimates of the quantities of various OCs in chinook salmon muscle tissue and eggs, reveal that between 22% and 40% of the quantities of these compounds are eliminated through spawning.