Acute Toxicity of Copper, Cadmium, and Mercury to the Freshwater Fish Varicorhinus barbatus and Zacco barbata

Abstract

Acute toxicities of copper, cadmium, and mercury to the freshwater fish Varicorhinus barbatus and Zacco barbata found in clear upstream waters were studied as a basis for the protection of river water quality and the ease of aquaculture pond management. In all cases, the higher the concentration of metal used, the quicker the animals died. Twenty-four-hour LC50 values of copper, cadmium, and mercury to V. barbatus were 0.305 mg/l Cu, 1.657 mg/l Cd, and 0.183 mg/l Hg; however 96-h LC50 values decreased to 0.246 mg/l Cu, 1.502 mg/l Cd, and 0.168 mg/l Hg,respectively. Similarly, 24-h LC50 values of copper, cadmium, and mercury to Z. barbata were 0.130 mg/l Cu, 2.598 mg/l Cd, and 0.201 mg/l Hg;96-h LC50 values were 0.079 mg/l Cu, 1.510 mg/l Cd,and 0.161 mg/l Hg,respectively. The order of metal toxicity to V. barbatus is Hg ＞ Cu ＞ Cd, while to Z. barbata it is Cu ＞ Hg ＞ Cd. To protect aquatic organisms, biologically safe concentrations of copper and mercury are suggested to be 7μg/l and 1.5μg/l,respectively. However more studies are needed to determine this level for cadmium.