Physiological effects of paraquat in juvenile African catfish Clarias gariepinus (Burchel 1822)

Objective: To investigate the physiological effects of paraquat in African freshwater catfish Clarias gariepinus. Methods: Two sublethal test concentrations of paraquat (1.37 and 2.75 mg/L) were chosen based on the 96 h LC50 value (27.46 mg/L). Some experimental fish were exposed to these concentrations and control group for 15 d. Peripheral blood samplings were taken at intervals for assessment of haematological and biochemical parameters. Results: Exposure to paraquat affected behaviour and morphology of Clarias gariepinus. There were significant decreases (P<0.05) in the mean values of hemoglobin, red blood cells, packed cell volume, cellular hemoglobin, and cellular hemoglobin concentration. The levels of white blood cells, glucose, aspartate aminotransferase, and alanine aminotransferase significantly increased (P<0.05) while protein levels declined. However, no definite pattern of changes was observed in the number and type of leucocytes. Conclusions: The results of the present study indicate that paraquat is toxic and has the potential to impair on the physiological activities in African catfish Clarias gariepinus. The use of paraquat should be strongly controlled and carefully monitored to avoid the possible damage done to the environment.