A behavioral assay for assessing effects of pollutants on fish chemoreception.

Behavioral assays are sensitive to sublethal levels of pollution but they usually require highly trained personnel and long observation periods. We describe a system that combines the sensitivity of a behavioral assay with commercially available automated monitoring equipment. The observation system consists of a special aquarium coupled to a recirculating water system, and an Opto-Varimex-Aqua activity tracking meter (Columbus Instruments, Columbus, Ohio) interfaced to a microcomputer. The tracking meter forms an intersecting, planar grid of light beams which, when interrupted by fish movements, is translated into a digitized signal and fed to the computer. The assay is based on the response of fish to natural chemical stimuli such as food odors or pheromones. When these stimulus solutions are injected into the water circulation the response of the fish is monitored by the computer system, which is capable of discriminating and quantifying changes in eight parameters. Normal responses to stimuli are compared with the response of fish that have been exposed to pollutants. We have successfully used this technique to examine effects of reduced pH on the response of fathead minnows, Pimephales promelas, to chemical feeding stimuli. The system should be easily adapted to any laboratory concerned with testing for effects of toxic substances, and will identify effects of pollution that have thus far been difficult or impossible to assess.