Approximately 100 large red drum (Sciaenops ocellata) died in the late spring of 1980 in the Mosquito Lagoon and the adjacent Indian River on the east coast of Florida. Several metals were present at high levels in organs taken from 2 affected fish. Concentrations of Cu, Zn, As, Cr, Cd, and Hg in the livers were greater than 5 standard deviations higher than the mean values measured in two control specimens. Gills from diseased fish were thickened and covered with a thick layer of mucus with edema the principle histological lesion. Moribund fish had serum concentrations of Na, Cl, K, and P0₄ markedly elevated (>10 S.D.) over control values indicating a failure of osmoregulation. Acute death was evident by the condition of the fish and the presence of food (blue crabs) in the stomachs. The fish apparently suffered an acute episode of metal poisoning since pesticides were not found in the liver or fat and there was no evidence of biological intoxication. Tests for cytopathic viruses were negative and bacteria were not cultured from the liver, spleen or kidneys. Known pathogens were not cultured from the lower digestive tract.

*Supported by special project funds from the Center for Environmental and Natural Resources Programs, Institute of Food and Agricultural Sciences, University of Florida.