Behavioural changes in freshwater fish, Cirrhinus mrigala (Hamilton) exposed to cypermethrin

The toxicity of insecticide cypermethrin to the freshwater fish, Cirrhinus mrigala was studied using static bioassay method. The 96 h LC50 was found to be 5.13 microg/l. Increase in opercular movement, loss of equilibrium, increase in surface behaviour, change in body colour, increase secretion of mucus, irregular swimming activity, rapid jerk movement, 'S' jerky, partial jerk, and aggressiveness were observed in fish exposed to lethal concentration of cypermethrin. But in sub lethal concentration changes were observed from that of lethal and with the approach of 14 and 21 day, fish attained to normalcy.