Ethological Response of Catfish Heteropneustes fossilis after Acute and Sub-acute Exposure of Cadmium

: Behavioural reactions are one of the most sensitive reactions of an organism to toxic materials. Heavy metals are among the most resistant pollutants having poor biodegradability. Cadmium is a black listed heavy metal that affects normal vital activities of fish including behaviour, colouration, physiology and haematology etc. Freshwater catfish, Heteropneustes fossilis were subjected to 96 hour LC 50 dose (392.92 mg/l) and 25% of 96 hour LC 50 dose (98.23mg/l) to evaluate toxic impact of cadmium on fish behaviour. The exposed animals showed avoidance, increased irritation, frequent surfacing, restlessness, fast opercular beat, irregular movement, loss of balance, poor food detection and consumption with increased air gulping. Peeling of skin, rashes, heavy mucus deposition, ulceration, haemorrhages on caudal and pectoral fins and colour fading was also noticed in exposed fishes. Possible underlying mechanisms of cadmium toxicity have been discussed.