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Abstract

Samples of fish from isolated and flow-through portions of Lake Chicot, Arkansas, were analyzed for residual pesticide concentrations from 1978 and 1981. Where appropriate ecologically, fish flesh, viscera and whole fish, were analyzed for the common organochlorine insecticides DDT [1,1 ,1-trichloro -2,2bis(p-chlorophenyl)-ethane], DDE [1,1-dichloro-2,2-bis(p-chlorophenyl)-ethyene], DDD [1,1-dichloro -2,2-bis(p-chlorophenyl)-ethane], toxaphene (chlorinated camphene), chlordane, heptachlor, heptachlor epoxide, dieldrin, and endrin. DDT, DDT metabolites, and heptachlor were significantly (a = 0.05) higher in spotted gar (Lepisosteus oculatus) and yellow bullhead catfish (Ictalurus natalis) than in other species examined. Pesticide concentrations did not exceed the acceptable levels established by the U.S. Environmental Protection Agency although toxaphene levels in one white crappie (Pomoxis annularis) and one freshwater drum (Aplodinotus grunniens) were as high as 0.01 /tg/g. Bottom feeding and piscivorus fishes had consistently higher concentrations of pesticides than fishes belonging to other feeding groups. The main body of the lake, with a large drainage area (930 km2 ) had higher concentrations of suspended solids than did the isolated northern basin and produced fish with significantly (a = 0.05) higher levels of toxaphene, DDD, and DDT. Insecticide concentrations were consistently greater in viscera with toxaphene, DDT, DDE and DDD levels significantly (a = 0.05) greater than in either whole fish or fish flesh samples. Eight years after banning, residual pesticides in fish from both basins of Lake Chicot were still significantly (a = 0.05) higher during years of increased runoff, indicating the importance of watershed management practices on longterm downstream water resources.

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