The use of bioindicators for assessing the effects of pollutant stress on fish

The use of bioindicators in environmental pollution studies involves monitoring a suite of selected stress responses at several levels of biological organization in order to (1) assess the effects of sublethal stress on fish, (2) predict future trends (early warning indicators) and (3) obtain insights into causal relationships between stress and effects at the community and ecosystem level. We have successfully applied this approach with redbreast sunfish ( Lepomis auritus) in freshwater systems receiving inputs of complex contaminant mixtures containing polychlorinated biphenyls (PCBs), hydrocarbons, heavy metals and chlorine. Indicators such as mixed-function oxidase (MFO) enzymes and DNA damage have provided direct evidence of toxicant exposure, while condition indices and indicators related to lipid biochemistry and histopathology have reflected impaired lipid metabolism, immune and reproductive system dysfunction, and reduced growth potential. At higher levels of organization, stress-mediated effects have included changes in the richness and biotic integrity of fish communities.