Temperature effects on acute copper toxicity to juvenile channel catfish Ictalurus punctatus

An experiment was conducted to evaluate the effect of temperature on the acute toxicity of copper sulfate to juvenile channel catfish (Ictalurus punctatus). Alkalinity and hardness were 30 and 26 mg l−1, respectively. The 7-10-g fingerlings were acclimated in four climate chambers at test temperatures of 21, 23, 25, and 27 °C for 2 weeks. After determining an acutely lethal copper dose, aerated tanks of 7.6 l were placed in each climate chamber in quadruplicate. To each, seven acclimated channel catfish fingerlings were added. The 72-h cumulative mortality from 20 mg l−1 copper sulfate was significantly lower in the 27 °C treatment (25%) compared to the 21, 23, and 25 °C treatments, where cumulative mortality was 79-96%. Total mortality at 72 h was significantly correlated (P<0.05) with decreasing temperatures (r=−0.91). This provides evidence of an inverse relationship between toxicity of copper sulfate and water temperature. Survival time, however, decreased with increasing temperatures.