Heavy metals bioaccumulation in tissues of Tilapia zilli as indicators of water pollution in kafinchiri reservoir, Kano - Nigeria

This study assessed the levels of heavy metals accumulation in water, gills and liver of Tilapia zilli fish collected from Kafinchiri water Reservoir for a period of four months with the aim of predicting health risk effect on consumers. Water and Tilapia zilli samples were collected from three different sites along the course of the dam; upstream, midstream and downstream. The concentration of copper, lead, chromium and cadmium in water and their accumulation in the liver and gills of the sampled fishes were determined using atomic absorption spectrophotometer. The results revealed that concentration of dissolved heavy metals in the water ranges from Cu (0.4mg/L- 0.6mg/L), Pb (0.9 mg/L – 1.4mg/L), Cr (undetected - 0.1mg/L) and Cd (0.01mg/L – 0.02mg/L). Accumulation in the gills of tilapia fish ranges from Cu (0.8μg/g – 0.85μg/g), Pb (0.3μg/g -0.9μg/g), Cr (≤0.1μg/g) and Cd was not detected. The accumulation of heavy metals in the liver were Cu (3.0μg/g – 5.4μg/g), Pb (2.7μg/g – 9.6μg/g) and Cr (0.1μg/g – 0.15μg/g) and Cd not detected. Water content chemical analysis indicated that; sampling point B (midstream) had the highest concentration of the heavy metals in which Pb recorded had the highest Bioaccumulation factor (BAF) of 5.76. The mean range of physicochemical parameters studied were temperature (25.90 – 27.37 °C), pH (7.60 – 8.52), DO (6.27 – 7.47mg/L), BOD (2.02 – 3.02mg/L), turbidity (28.05 - 34.00 NTU), electrical conductivity(187.60 – 361.17μS/cm), TDS (211 - 363mg/L), Total dissolved solids, electrical conductivity, turbidity and nitrate recorded significant difference between sites (P<0.05). It was believed that domestic activities around the reservoir is the major contributing factor to the accumulation of toxic heavy metals in fish examined. It is recommended that intervention by relevant authorities is needed curtail potential long term effect of this pollutants in the reservoir.Key words: Heavy metals Pollution, Tilapia zilli, Bioaccumulation, Kafinchiri Reservoir