EVALUATING TOXICITY INFLUENCE OF PARAQUAT DICHLORIDE ON THE WATER QUALITY AND HISTOPATHOLOGY OF Oreochromis niloticus FINGERLINGS

This study investigated the acute toxicity of paraquat dichloride to water quality and Oreochromis niloticus fingerlings. Fish with average length and weight of 4.2cm and 0.4g respectively were stocked at 10 fish per aquarium, acclimatized for 2 weeks and fed twice daily at 5% body weight with 40% crude protein diets. Feeding was stopped 24 hours before bioassay and experimental fingerlings were exposed to test concentrations (treatments) of paraquat dichloride at 0 mg/l (A), 3.33 mg/l (B), 6.66mg/l (C), 10 mg/l (D) and 13.3 mg/l (E) each containing the active ingredient at 0 mg/L, 1.7 x 10 -3 mg/L, 3.3 x 10 -3 mg/L, 5 x 10 -3 mg/L and 6.7 x 10 -3 mg/L respectively with each treatment replicated thrice. The LC 50 was 4.90 mgL -1 and significant differences (P<0.05) were observed in the mean values of Dissolved Oxygen (DO), Chemical Oxygen Demand (COD) and pH. Signs of respiratory stress, erratic swimming and sudden quick movement were observed in experimental fish. This increased with increase in test concentrations. Histopathological studies showed areas of lesion and necrosis. Strict adherence to recommended herbicide dosages during application is therefore essential most especially in the flood prone areas so that they do not eventually accumulate in aquatic systems