ABSTRACT
The study evaluated the toxicological effects of paraquat on Oreochromis niloticus fingerlings. Two hundred and sixteen (216) fingerlings (Average weight: 7.50g) were purchased from a local farmer in Ikole-Ekiti, Ekiti State, Nigeria and were transported to the Wet Laboratory of the Department of Fisheries and Aquaculture, Federal University Oye-Ekiti, Nigeria and acclimatized for two weeks. After range finding test, the fish were exposed to acute concentration of 2.96 mg/I, 3.3lmg/L, 3.86mg/L ,4.4mg/L and 4.97mg/L of paraquat for 96 hours while the first treatment contained no paraquat (0.00mg/1). Fish were distributed in triplicate (12 fish per tank) into 20 litres plastic tanks. Physiochemical parameters of water were taken. Fish behavior and mortality were observed and recorded. Probit analysis was used to determine the lethal concentration of paraquat on Nile tilapia. Results of bioassay procedure showed that the LC50 after a 96 hours was 3.85mg//l. Restlessness, erratic swimming, loss of equilibrium, discolouration, and sudden fish death were observed in the exposed fish and these varied greatly with differences in concentration of the toxicant and this shows that mortality increased with an increase in concentration. The differences observed in the mortalities of Oreochromis niloticus at varying concentrations were significant (p
