Toxicological Responses of African Mud Catfish (Clarias gariepinus, Burchell, 1822) Fingerlings Exposed to Culture Water Contaminated with Different Concentrations of Cypermethrin

The toxicological effects of cypermethrin on Clarias gariepinus fingerlings and its contamination of culture water was studied. Ten fingerlings were stocked in each aquarium and was exposed to 5 different concentrations of cypermethrin and there was a control group. The fingerlings were exposed to 5, 10, 15, 20 and 30 ppm of cypermethrin in triplicate. A total of 180 C. gariepinus fingerlings with a mean weight of 1.85 ± 0.29 g were used throughout the study. The toxicant altered the physico-chemical parameters of culture water. The water temperature, pH, electrical conductivity and turbidity of the contaminated culture water increased with increase in the concentration of cypermethrin, while the dissolved oxygen (DO) decreased with increase in the toxicant concentration. Temperature, conductivity, pH and turbidity values were higher and the DO level was lower in the aquarium contaminated with the highest concentration of the toxicant compared to the control group. Statistically, the physico-chemical parameters varied significantly between the culture waters contaminated with different concentrations of cypermethrin across all exposure durations at p<0.05, except for temperature over 96 hours exposure period which was insignificant at p>0.05. The water temperature, pH and conductivity of the culture water were within the WHO acceptable limits except the dissolved oxygen (30 ppm group over 72 and 96 hour exposure duration) and turbidity (5, 10, 15, 20 and 30 ppm group) which were above the World Health Organisation (WHO) permissible limit. The mortality data trend of fingerlings exposed to cypermethrin was concentration and duration dependent. The 96 hours LC50 value with 95% confidence limit of C. gariepinus fingerlings exposed to the toxicant was 9.332 ppm ± 0.839, and was significant with a determination coefficient (r2) of 0.88 at P<0.05. The low LC50 value for the fingerlings exposed to the pesticide indicated its high toxicity. In conclusion, contamination of culture water with cypermethrin led to the mortality of C. gariepinus fingerlings and the alteration of the physico-chemical parameters of the culture water. As a result, more similar research should be carried-out involving haemathological, reproductive, histological and other physiological alterations when fishes are exposed to cypermethrin so as to further reveal the toxic and harmful potentials of pesticides.