Contaminant trends in lake trout (Salvelinus namaycush) from the Upper Great Lakes

Abstract

Contaminant body burdens in lake trout (Salvelinus namaycush) from the Upper Great Lakes have been monitored since 1970 on Lake Michigan and since 1977 and 1978 on Lakes Superior and Huron by United States Environmental Protection Agency (USEPA), Great Lakes National Program Office and U.S. Fish and Wildlife Service (USFWS), Great Lakes Fishery Laboratory. Analysis of the Lake Michigan data shows that mean polychlorobiphenyl (PCB) concentrations declined from a maximum of 22.91 mg/kg in 1974 to 5.63 mg/kg in 1982. Mean total DDT concentrations declined from 19.19 mg/kg in 1970 to 2.74 mg/kg in 1982. The decline in both contaminants closely followed first order loss kinetics. If the current declines continue, PCB concentrations will decline to the U.S. Food and Drug Administration (USFDA) tolerance of 2.0 mg/kg in 1988. Mean total DDT concentrations will fall to the International Joint Commission (IJC) objective of 1.0 mg/kg by 1991. Mean dieldrin concentrations increased significantly from 0.20 mg/kg in 1971 to 0.58 mg/kg in 1979 before declining to 0.21 mg/kg in 1982. The decline from 1979–1982 followed first order loss kinetics. As this decline is not reflected in other species (bloater chubs, smelt) it will require additional years of monitoring to determine if dieldrin concentrations between 1979 and 1982 truly represents a declining trend. The only statistically significant trend other than in Lake Michigan was for total DDT which declined significantly in Lake Superior lake trout. Large data variance and the short time frame covered (1977–1982) interfered with detection of trends on Lakes Superior and Huron.