Acute Toxicity of Paraquat Herbicide (Dichloride) on Survival and Behaviors of African Catfish (Clarias gariepinus Burchell,1822) Juveniles

This study assessed the 96-hours acute toxicity of paraquat herbicide on juvenile African catfish (Clarias gariepinus). A static bioassay was conducted using a completely randomized design with six concentrations of paraquat (0.00, 0.80, 1.10, 1.40, 1.70, and 2.00 mg/L). A total of 180 juveniles were acclimatized for 14 days and exposed to the test solutions, with ten fish per treatment in triplicate. Mortality, survival, and behavioral responses were monitored at regular intervals. Exposed fish exhibited concentration-dependent behavioural abnormalities, including frequent air gulping, weakness, agitated swimming, vertical positioning, excessive mucus secretion, and loss of equilibrium, indicating respiratory distress and neurotoxicity. Mortality increased with both concentration and exposure duration, ranging from 20% at 0.80 mg/L to 90% at 2.00 mg/L, while no mortality was observed in the control group. Probit analysis revealed a 96-hours median lethal concentration (LC₅₀) of 1.41 mg/L, confirming the high toxicity of paraquat to juvenile C. gariepinus. The findings demonstrate that paraquat poses a significant threat to freshwater fish and may adversely affect aquatic ecosystems, highlighting the need for strict regulation of its use near water bodies.