Epizoology of Hepatic Neoplasia in Atlantic Tomcod (Microgadus tomcod) from the Hudson River Estuary

Atlantic tomcod (Microgadus tomcod) collected from the Hudson River estuary during the winter spawning season revealed neoplastic and preneoplastic 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 hepatocellular carcinoma frequently involving the entire liver. Lesions were more prevalent in larger individuals within the same age group, suggesting a relationship between growth rate and tumor expression. Atlantic tomcod from a relatively unpolluted estuary in Connecticut did not reveal a comparable prevalence of hepatic lesions. Juvenile tomcod collected from the Hudson during the summer, only 4–5 mo prior to the winter spawning season had no hepatic lesions, suggesting that these lesions form rapidly, coincident with gonadal maturation. Chemical analysis of liver tissue revealed high levels of PCBs (2.5–38.2 mg/kg) and the presence of several pesticides including DDT (and metabolites), chlordane, 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 lower estuary nursery areas, coupled with high-temperature stresses of summer, may contribute to the high levels of hepatic lesions observed.