RESPONSE THRESHOLD LEVELS OF SELECTED ORGANIC-COMPOUNDS FOR RAINBOW-TROUT (ONCORHYNCHUS-MYKISS)

The responses of 27 organic compounds, mainly chloromethanes, -ethanes, -ethenes, and -phenols, were investigated by exposing rainbow trout fingerlings to low microgram-per-liter concentrations in a darkened flow-through system for up to 1 h. Responses by the fish were followed continuously by observing ventilation rates (frequency and amplitude), swimming patterns, and general activity using the low-voltage electric fields generated by the fishes' activity. The lowest level of response was found for trichloroethylene at 5 mu g/L. Dichloromethane, 1,1- and 1,2-dichloroethane, 1,1,1- and 1,1,2-trichloroethane, cis-1,2-dichloroethylene, I,3-dichloropropene, and allyl acetate were responded to at concentrations of 10 mu g/L, carbon tetrachloride at 15 mu g/L, and 4-chlorophenol and 2,4-dichlorophenol at levels of 30 mu g/L. Unsubstituted phenol was not responded to at levels of up to 50 mu g/L.