Acute Nickel Toxicity Responses of Labeo rohita and Cirrhinus mrigala

The exposure of acute nickel toxicity (96-hr LC 50 and lethal concentrations) for two fish species viz. Labeo rohita and Cirrhinus mrigala was determined in this study. During metal stress trials both species were kept at constant temperature (32C), pH (7) and hardness (250 mg L -1 ) of water. Physico-chemical parameters of test medium were monitored regularly. The observed mean LC 50 and lethal concentrations for Cirrhinus mrigala were 55.85 2.84 and 128.44 9.25 mg L -1 , respectively. On the other hand, for Labeo rohita, mean values of LC 50 and lethal concentrations were calculated as 56.42 2.51 and 120.98 7.18 mg L -1 , respectively. Cirrhinus mrigala had lower LC 50 but higher lethal dose. Two fish were different in size as well. A significant positive correlation of metallic ion concentrations was observed with sodium, potassium, carbon dioxide and electrical conductivity whereas an inverse relationship was obtained with dissolved O 2 for both Labeo rohita and Cirrhinus mrigala test mediums. It is concluded that acute concentration of nickel is lethal for both fish species with a significant difference of LC 50 and lethal concentrations among two fish species.