Organochlorine Residues in Fish from the Yazoo National Wildlife Refuge

Toxaphene and DDTR (DDT plus metabolites), both exceeding 10 ppm wet weight, were found in all samples of fish collected from 9 locations on the Yazoo, Mississippi, National Wildlife Refuge. Concentrations were highest in aquatic systems receiving direct inflow from areas draining agricultural land, and lowest in areas receiving only backwater overflow or local runoff. Residue levels of toxaphene and DDTR were high enough to threaten fish-eating wildlife. Installation of flood control structures around the northern perimeter of the refuge may reduce the inflow of contaminants that now accumulate in resident biota.