Effects of pesticide (Chlorpyrifos Ethyl) on the fingerlings of catfish (Clarias gariepinus)
Acute toxicity bioassay of the organophosphate pesticide chlorpyrifos ethyl on the fingerlings of Clarias gariepinus was evaluated to determine its effect on the survival, body morphology and the lethal concentration (LC50). Following a preliminary bioassay in mg/l concentration which showed 100% mortality, fish were exposed to three replicate serial concentrations of 0.5, 1.0, 2.0 and 4.0 μg/l for 96 h. As soon as fish were transferred to the toxicant there was corresponding abnormal behaviour, characterized by restlessness uncoordinated swimming, loss of equilibrium, increase in opercula beats and air gulping, indicating respiratory stress. The effect of the toxicant is concentration and time dependent. The lethal concentrations (LC50) of chlorpyrifos ethyl on the fingerlings of Clarias gariepinus for 24,72 and 96 hr were 2.0,1.0 and 0.5 μ /l respectively. Toxicant exposed fish also showed pinkish coloration at the caudal peduncle (tail region) and the operculum indicating of haemorrhage or damage to the tissue, resulting from respiratory stress. In conclusion, fish farmers are advised to take adequate precaution to prevent excessive use of organic pesticides such as chlorpyri for ethyl because of the possible loss to fish production.