Effect of Ambient Temperature and Daylight on the Survival of Freshwater Catfish Heteropneustes fossilis (Bloch, 1794) Exposed to Cypermethrin

Short-term static bioassays were made to evaluate effects of ambient temperature and daylight on the survival of freshwater catfish Heteropneustes fossilis to a lethal dose (1 mu g/L) of cypermethrin. The results revealed that light hour exposure period (10 h) remaining constant, there was no mortality up to an ambient temperature of 3 degrees C. Fish started dying as ambient temperature increased to 4 degrees C and the mortality increased linearly with increase of temperature until 100% mortality was observed at an ambient temperature of 22 degrees C. But mortality of the fish decreased with the increase of light hours at a constant ambient water temperature of 3 degrees C.