Biotolerance of Orechromis niloticus to Nickel (Ni) Inside the Agodi Reservoir at Ibadan, Nigeria

Orechromis niloticus (Tilapia) that was rarely found in feeder Ogunpa River was more invasive in the receiving Agodi Reservoir and this provoked an examination of the remote causes. .Sampled water temperature and pH were measured with standard analytical methods while Ni, Co and Cr concentrations in water and fish were selectively tested using Atomic Absorption Spectrophotometer (AAS).Data obtained were subjected to analysis of variance and linear regression to establish clear relationships. On the average, temperature was 27.15ºC, pH 7.56, Ni 0.27 mg/L, Co 0.75 mg/L and Cr 0.005 mg/Lin Ogunpa River, while in Agodi Reservoir, temperature was 27.42ºC, pH 7.57, Ni 0.17 mg/L, Co 0.19 mg/L and Cr 0.005 mg/L. The temperature and pH values were higher in Agodi Reservoir than in the Ogunpa River but only the concentrations of Ni and Co in Ogunpa River were higher than in Agodi Reservoir. Using the FAO/WHO permissible limits, only the Ni concentration appeared potent in influencing Tilapia eco-dynamics. Ni accumulation could be lethal and must have affected the fish relocation and distribution, thus, a conclusion that Ni concentration and its synergistic effects with temperature could be responsible for the migration of the fish into the Agodi Reservoir.