CONTAMINANTS IN FISHES FROM GREAT-LAKES-INFLUENCED SECTIONS AND ABOVEDAMS OF 3 MICHIGAN RIVERS .1. CONCENTRATIONS OF ORGANO-CHLORINE INSECTICIDES, POLYCHLORINATED-BIPHENYLS, DIOXIN EQUIVALENTS, AND MERCURY

Fishes of the Great Lakes contain hazardous chemicals such as syntheti c halogenated hydrocarbons and metals. These fish can move from the la kes into the Great Lakes tributaries of Michigan. In doing so, they tr ansport concentrations of contaminants which may represent a risk to w ildlife. Concentrations of mercury (Hg), total polychlorinated bipheny ls (PCBs), 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TCDD-EQ), total DDT complex, aldrin, endrin, dieldrin, heptachlor, heptachlor ep oxide, lindane, hexachlorobenzene, cis-chlordane, oxychlordane, endosu lfan-I, methoxychlor, trans-chlordane, and trans-nonachlor were determ ined in composite samples of fishes from above and below Michigan hydr oelectric dams, which separate the fishes which have access to the Gre at Lakes from fishes that do not. Mean concentrations of total PCBs, T CDD-EQ, DDT, and most of the other pesticides were greater in composit e samples of six species of fishes from below than above the dams on t he Au Sable, Manistee, and Muskegon Rivers. Concentrations of mercury, were the same or greater above the dams than below. However, this dif ference was statistically significant only on the Au Sable. Mercury co ncentrations ranged from less than 0.05 mg/kg to 0.73 mg Hg/kg, ww. To tal concentrations of PCBs ranged from 0.02 to 1.7 mg/kg, ww. Concentr ations of 2,3,7,8-tetrachlordibenzo-p-dioxin equivalents varied among fishes and locations. The concentrations of TCDD-EQ ranged from 2.4 to 71 mug/kg, ww, with concentrations in carp being the greatest. Concen trations of TCDD-EQ were greater than the concentrations which would b e expected to occur, due solely to the presence of polychlorinated dib enzo-p-dioxins (PCDD), polychlorinated dibenzofurans (PCDF), and techn ical mixtures of PCBs.