ACUTE TOXICITY OF FORMALIN AND COPPER-SULFATE TO STRIPED BASS FINGERLINGS HELD IN VARYING SALINITIES

Striped bass fingerlings, Morone saxatilis, held at varying salinities were exposed to various concentrations of formalin and copper sulfate, and tolerance values were determined by calculating 96-h LC50 values through probit analysis. The 96-h LC50 values for the formalin toxicity tests were: 4.96 mg/l, 13.52 mg/l, 15.48 mg/l and 10.84 mg/l for 0, 5, 10, and 15 ppt salinity, respectively. The copper sulfate toxicity tests yielded 96-h LC50 values of: 2.68 mg/l, 8.08 mg/l and 7.88 mg/l for 5, 10 and 15 ppt salinity, respectively. The results indicated a significant variation in tolerance levels due to changes in salinity. Regression models derived for both tests showed an increase in tolerance as salinity approached that which the fish were acclimated to prior to testing (10 to 13 ppt). Beyond this point, tolerance to either chemical decreased. This evidence suggests a compounded effect of chemical and environmental interaction (i.e. salinity) on survival and possible disruption of normal gill function since previous studies have shown these chemicals to cause gill damage. These pathological changes can severely impair osmoregulation and/or respiratory activity. This phenomenon may also be associated with osmotic stress brought about by the absence of an acclimation period prior to the experiments to the salinities tested. © 1990.