Use of Fish Ventilation Frequency to Estimate Chronically Safe Toxicant Concentrations

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Abstract
A 96 h toxicity test with fish ventilation frequency as the response variable was developed to estimate safe Zn concentrations for steelhead Salmo gairdneri. Two Oregon [USA] steelhead strains were exposed to Zn at different water temperatures and total hardnesses (7, 12 and 17.degree. C; 25 and 125 mg/l as CaCO3). Ventilation frequencies enumerated from bioelectric potentials generated by buccal and opercular openings and closing showed significant increases at the highest test concentration in 5 of 10 tests. At 12.degree. C and 25 mg/l hardness, responses were detected at a Zn concentration of 144 .mu.g/l; the safe concentration determined in a chronic exposure of embryos and juveniles was between 444 and 819 .mu.g Zn/l. This indicates that ventilation-frequency tests are at least as sensitive as long-term toxicity tests and may be used to screen chemicals for potential harmful effects on fish.