Assessment of Trace Elements Concentration in Tissues of Tilapia Fish (Tilapia guineensis) from Badagry Creek, Nigeria

Aims: To determine trace element (Fe, Cu, Pb, Zn, Cr and Cd) concentrations in Tilapia guineensis tissues from Badagry creek, and to test hypotheses of (1) no significant difference in the element concentrations in muscle, liver, gill and kidney of Tilapia guineensis and (2) the observed concentrations in fish tissues do not exceed the limits in fish for human consumption.

Study Design: Stratified random sampling.

Place and Duration of Study: Designated fishermen landing points around Badagry creek, Nigeria. Quarterly between November, 2012 and September, 2013.

Methodology: I randomly sampled Tilapia guineensis from the fishermen catches in the selected landing points of Badagry creek. In the laboratory, extraction and digestion of tissues (muscle, liver, gills and kidney) of specimen fishes were done using standard methods. The concentrations of Fe, Cu, Pb, Zn, Cr and Cd in the digested fish tissues specimens (filtrate) for each set of samples were measured using Atomic Absorption Spectrophotometer (Spectra AA-240, Agilent Technologies) with air-acetylene flame.

Results: Mean concentrations in muscle, liver, gill and kidney respectively, expressed in mg/kg dry weight were 30.18, 122.29, 168.89 and 41.30 for Fe, 0.32, 5.27, 2.51 and 1.54 for Cu, 13.87, 15.10, 17.86 and 20.11 for Pb, 17.15, 15.32, 30.73 and 11.58 for Zn, 94.60, 98.93, 134.67 and 150.51 for Cr and Below Detection Limit (BDL), BDL, 0.06 and BDL for Cd. The concentration of iron in gills was significantly higher than liver, kidney and muscles (P =.02). Zinc concentration was also significantly higher in gills than in muscle, liver and kidney (P =.00). Average metal concentrations in muscle, liver, gill and kidney decrease in the following magnitude orders respectively: Cr>Fe>Zn>Pb>Cu>Cd; Fe>Cr>Zn>Pb>Cu>Cd; Fe>Cr>Zn>Pb>Cu>Cd; Cr>Fe>Pb>Zn>Cu>Cd. Element concentrations in fish edible tissues were below the FAO/WHO limits except for Pb and Cr.

Conclusion: The concentrations of Pb and Cr in examined edible fish were posing a public health hazard and calls for continuous monitoring by relevant authorities/agencies.