Acute toxicity of synthetic pyrethroid cypermethrin to freshwater catfish Heteropneustes fossilis (Bloch).

Lethal concentrations of cypermethrin, dissolved either in water or acetone, were determined for freshwater catfish Heteropneustes fossilis at different hours of exposure by static bioassays. Up to 48 hours, there was no difference between LC(50) values of aqueous and acetone solublized cypermethrin. Seventy-two-hour LC(50) values of aqueous cypermethrin and acetone solublized cypermethrin to H. fossilis were 0.67 and 1.27 microg/L, respectively. Lethal values remained unchanged beyond 72 hours. The fish exposed to even lower concentration of cypermethrin (0.5 microg/L) showed hyperactivity.