Biomarkers indicate health problems in brown bullheads from the industrialized Schuylkill River, Philadelphia

We used biomarkers to assess the health of two populations of brown bullhea ds Ameiurus nebulosus, one from an urban, industrialized section of the Sch uylkill River (SR), Philadelphia, Pennsylvania, and the other from Hopkins Pond (HP), in suburban New Jersey, which was not affected by industry. We e valuated health using histopathology, condition factor (K), hepatosomal ind ex (HSI), prevalence of parasites, health assessment index (HAI), and popul ation age structure. Sediment analysis revealed that both sites contained s imilar levels of polynuclear aromatic hydrocarbons (PAHs). Brown bullheads from the SR were longer and heavier than brown bullheads from HP and exhibi ted more external lesions. There were no hepatic lesions in brown bullheads from either site. Condition factor was higher in SR fish, but due to lengt h differences between the two populations, was not a reliable indicator of general health. Hepatosomal index was similar between both populations, alt hough the presence of numerous cestodes in the visceral organs, including t he liver, of HP brown bullheads confounded the interpretation of the HSI. T he incidence of parasitism was significantly greater in HP fish than in SR fsh. The HAI was significantly greater in SR brown bullheads, indicating mo re organ abnormalities in SR fsh than in HP fish, including more abnormalit ies of the fins, barbels, and mouth. Population age structure was older for HP brown bullheads than for SR fish, indicating a shorter lifetime for SR brown bullheads. Although PAH levels were similar between the two sites, SR brown bullheads were less healthy than HP brown bullheads, as indicated by several biomarkers. Histopathology, health assessment index, and populatio n age structure were the most informative biomarkers.