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 (32°C), 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. Novelty Statement | The study is novel in recommending continuous monitoring of metal contamination in fish species to ensure the sustainability of this food for human consumption.