Heavy metal content of two major commercial fish species of Cross River Estuary, Mbo Local Government Area, Akwa Ibom State, Nigeria

Abstract

Heavy metal pollution of aquatic environments is increasing all over the world in recent years. Under certain environmental conditions, fish may concentrate large amounts of some heavy metals from the water in their tissues. This study assessed the concentration of lead, copper, cadmium, chromium and zinc in two commercially important fish species, Pseudotolithus senegalenses and Ethmalosa fimbriata from Cross River estuary of Akwa Ibom State, Nigeria. The concentrations of these metals were analyzed using atomic absorption spectrophotometer (UNICAM) by direct aspiration of samples into air acetylene flame. Pseudotholithus senegalenses had 0.023±0.02, 2.15±0.50, 0.08±0.04, 0.06±0.07 and 5.59±0.94 mg kg^-1 as the mean concentration of lead, copper, cadmium, chromium and zinc respectively, while Ethmalosa fimbriata had 0.05±0.01, 1.23±0.29, 0.04±0.01, 0.60±0.24 and 4.35±0.80 mg kg^-1 as the mean concentration of these metals. The overall mean concentration of each heavy metal varied significantly (p<0.05) depending on the species of fish and according to month of sampling. This study reveals that the levels of these metals were below the recommended maximum limit for human consumption. However, effort should be made to avoid future contamination of the water body and subsequently the fish living in it since their synergistic effect can still pose a very serious health problem.

Keywords: Bioaccumulation, lead, perturbation, pollution, zinc