Determination of Lethal Concentration of Copper Compounds on Nile Tilapia (Oreochromis niloticus Linnaeus, 1758) Larvae

Abstract

Copper is an essential element for cell organisms. However, irregularity copper level could have effect on the growth of organism. In this research, we aim at consideration of copper compounds toxicity against larvae of Nile tilapia (Oreochromis niloticus Linnaeus, 1758) by statistic assays. Four days old of test fish had an average 7.10±0.03 mm of length and 9.72±0.04 mg of fresh weight. All experiments were carried out for a period of 48 to 96 hours at 27–30°C. The number of dead fish was counted every 24 hours and the mortality rate was determined after 96 hours. The statistical data was evaluated by Finney’s probit analysis method. The fish died 50% (LC₅₀ 95% confidence limits) after 48, 72, 96 hours of concentration copper chloride (CuCl₂) 595.75, 231.11, 124.64 μg/L, respectively, and copper nitrate (Cu (NO₃)₂) 1,025.40, 588.79, 456.50 μg/L, respectively. The LC₅₀ results clearly show that copper compounds toxicity for fish increased with increasing concentration and exposure time. The percentage of survival decreased with increasing of both copper compound concentrations and it was significantly different from control (p<0.01). This study showed that Nile tilapia larvae were more sensitive to copper chloride than copper nitrate. Further study needs the processes by which these chemicals affect biochemical changes of the fish.