EPIZOOLOGY OF HEPATIC NEOPLASIA IN ATLANTIC TOMCOD (MICROGADUS TOMCOD) FROM THE HUDSON RIVER ESTUARY

Atlantic tomcod (Microgadus tomcod) collected from the Hudson River es tuary during the winter spawning season revealed neoplastic and preneo plastic lesions in livers from 44% of the age 1 individuals and 93% of the age 2 individuals collected. These lesions appear as a continuum ranging from basophilic foci with little cellular alterations to hepat ocellular carcinoma frequently involving the entire liver. Lesions wer e more prevalent in larger individuals within the same age group, sugg esting a relationship between growth rate and tumor expression. Atlant ic tomcod from a relatively unpolluted estuary in Connecticut did not reveal a comparable prevalence of hepatic lesions. Juvenile tomcod col lected from the Hudson during the summer, only 4-5 mo prior to the win ter spawning season had no hepatic lesions, suggesting that these lesi ons form rapidly, coincident with gonadal maturation. Chemical analysi s of liver tissue revealed high levels of PCBs (2.5-38.2 mg/kg) and th e presence of several pesticides including DDT (and metabolites), chlo rdane, and dieldrin (<0.1-3.0 mg/kg) and several heavy metals (<0.1-6. 5 mg/kg). These results suggest that chemical contamination of the low er estuary nursery areas, coupled with high-temperature stresses of su mmer, may contribute to the high levels of hepatic lesions observed.