Temperature preference as an indicator of the chronic toxicity of cupric ions to Mozambique tilapia.

Evaluation of the effects of environmental contaminants on aquatic communities has focused primarily on acute bioassays. These bioassays provide rapid and reproducible concentration response curves based on death as an endpoint. In recent years, however, emphasis has shifted towards monitoring sublethal effects of toxicants (e.g. modification of behavioral patterns, growth, reproduction), because a greater community biomass is generally exposed to chronically low levels of pollutants than to lethal levels (Kleerkopper 1976). Toxicological modification of specific behavioral patterns is often associated with the ability of a fish to survive environmental perturbations. Changes in fish behavior, however, may be complex and difficult to detect in the laboratory. An effective test, therefore, for evaluating the effects of aquatic contaminants on fish behavior must include a well-defined and quantifiable endpoint.