Investigation on acute toxicity and behavioral changes in a freshwater African catfish,Clarias gariepinus (Burchell,1822),exposed to organophosphorous pesticide,Termifos®

Chlorpyrifos (cpf) o,o-diethyl 0,3,5,6-trichloropyridin-2yl phosphorothioate is commonly used for pest and insect control in agricultural fields and surrounding freshwater reservoirs. a 96 h semi-static acute toxicity bioassay was carried out to determine the lc50 value and behavioral responses of commercial formulation of chlorpyrifos (termifos) on the freshwater fish clarias gariepinus. the lc50 values (with 95 % confidence limits) of different concentrations of cpf (termifos) in c. gariepinus were found to be 1.66 (1.40-3.30),1.30 (1.18-1.53),1.03 (0.98-1.11) and 0.86 (0.73-0.99) mg/l for 24,48,72 and 96 h exposure time,respectively,thus indicating that the pesticide is highly toxic to the fish. the values of safe level of the pesticide in c. gariepinus varied from 8.61×10-2 - 8.61×10-6 mg/l. fish exposed to various concentrations of the pesticide showed uncoordinated behavior such as erratic and jerky swimming,attempt to jump out of water,frequent surfacing and gulping of air,decrease opercula movement and secretion of mucus on the body and gills followed by exhaustion and death. our results indicate that commercial formulation of chlorpyrifos (termifos) is highly toxic to c. gariepinus. the pesticide should thus be applied with caution in our environment especially near water bodies to avoid the possible risk associated with its use. copyright 2013 zoological society of pakistan.