Bio-concentration of some heavy metals and oxidative stress enzymes in <i>Oreochromis niloticus</i> (Tilapia fish) from the Hadejia- Nguru wetlands, Jigawa State.

Abstract

The Hadejia- Nguru wetland is a vast land of intensive agricultural and fishing activities. It receives waste water through discharges from agricultural, sewage and industrial sources. Five points marked as sites A,B,C,D and E were used for the study .The study aimed in evaluating levels of some heavy metals Cadmium(Cd), Chromium(Cr), Aluminum(Al),Lead(Pb) and Mercury(Hg) in O. niloticus and their effect in inducing oxidative stress in the fish. The tissue of interest were gills, muscle and liver. Results obtained revealed concentration of heavy metal in the sequence Hg>Cr>Pb>Al>Cd in the fish. The highest level of heavy metals contamination was recorded in fish from sample site B. There was significant difference (P<0.05) in fish from site B compared with sites C, D and E. Mean concentration of Hg recorded in the gills ranged from 249.75 mg/kg in site B to 128.50 mg/kg in site A, 118.75 mg/kg in site D, 77.25 mg/kg in site C and 62.0 mg/kg in site E. Oxidative stress markers such as superoxide dismutase, catalase, lipid peroxidation and reduced glutathione were significantly higher in the fish tissue indicating a stressful condition in the fish. Anthropogenic activities contributed to the high level of metals found in the wetland and this in turn is reflected in the oxidative stress in fish.