Acute toxicity of copper sulfate to the two specifications of Schizothorax wangchiachii fry

【Objective】To determine the resistance of Schizothorax wangchiachii fry to copper sulfate, and provide reference for safe and efficient medication in the breeding of S. wangchiachii fry.【Method】Under the conditions of water temperature of(7.3±0.3)℃, dissolved oxygen of 7.9 mg/L, pH 7.8, CaCO₃ hardness of 41.2±0.7 mg/L, light(12 h:12 h) of 100 lx, no inflating, no feeding, one-year-old S. wangchiachii fry and ten two-year-old S. wangchiachii fry were materials. Prepared different concentrations of copper sulfate solution to simulate the drug bath process. The tolerance of the fry to copper sulfate was assessed based on the linear relationship of cumulative mortality(probability unit) and copper sulfate concentration logarithms, semi-lethal concentration(LC₅₀), 95% confidence interval and safety concentration(SC).【Result】One-year-old S. wangchiachii fry and ten two-year-old S. wangchiachii fry were soaked in copper sulfate solution. The results showed that time of fry beginning of dying and the logarithm of the testing concentrations had a negative linear correlation, and there was positive linear correlation between the cumulative mortality rate at both 24 and 48 h and testing concentrations. LC₅₀ of one-year-old S. wangchiachii fry soaked in copper sulfate solution for 24 and 48 h were 1.018 and 0.870 mg/L, 95% confidence intervals were0.944, 1.092mg/L and0.459, 1.281mg/L, SC was 0.191 mg/L. LC₅₀ of two-year-old S. wangchiachii fry soaked in copper sulfate solution for 24 and 48 h were 4.222 and 1.011 mg/L, 95% confidence intervals were3.775, 4.670mg/L and0.421, 1.602mg/L, and SC was 0.017 mg/L. No poisoning or death occurred in one-year-old S. wangchiachii fry and ten two-year-old S. wangchiachii fry when soaked in common concentration(7.143 mg/L) of copper sulfate solution for 3 h, and no abnormal situation occurred 3 h post soaking. The cumulative mortality curve of one-year-old S. wangchiachii fry and ten two-year-old S. wangchiachii fry soaked in common concentration was oblique wavy with two bulges but no intermediate period. The death frequency of fry was M shape dis-tribution, which was second-order Gaussian distribution.【Conclusion】Acute toxicity of copper sulfate to one-year-old S. wangchiachii fry and two-year-old S. wangchiachii fry can be listed as highly pesticide, and the resistance of two-year-old S. wangchiachii fry is relatively high. But the resistance of S. wangchiachii fry to acute toxicity of copper sulfate is low. High concentration and short time medicine bath are suggested to prevent the disease of S. wangchiachii fry in actual production.