Acute toxicity bioassay of organophosphorus pesticide, chlorpyrifos on freshwater catfish, Heteropneustes fossilis (Bloch, 1794)

Abstract

Chlorpyrifos (CPF) is common pesticide. It reaches to water bodies though surface runoff and affecting the aquatic biota. The objective of the present study was to observe seasonal variation in acute toxicity of CPF with behavioural and morphological changes in freshwater catfish, Heteropneustes fossilis. This study was conducted by exposing the adult fish to different concentrations of chlorpyrifos (0.002-2.28 m.M.l-l) for 96 h along with control groups in resting (December), preparatory (February), and prespawning (April) phase. The data were subjected to get LC50 and safe concentration in respective season. Susceptibility of catfish, H. fossilis to lethal effects of CPF was found to be both duration and concentration dependent. The LC50 values for CPF were found to be minimum during pre-spawning phase and maximum in resting season. Their tolerance to CPF was increasing with inactiveness of gonadal activity (resting season). At higher concentration of CPF, fish showed alterations in morphological and behavioural responses, especially erratic and jerky swimming, frequent surfacing and in gulping, mucus secretion, an increase in opercular movement and copious secretion of mucus all over the body. As per results, different reproductive phase fish responded different to toxicant concentrations.