Heavy metal evaluation and bioaccumulation status of selected fish species of River Gongola, Gombe State, Nigeria

Abstract

Fish and other aquatic creatures are seriously threatened by chemical pollutants such as heavy metals that contaminate the aquatic environment. This could have long-term consequences for the human food chain. The aim of the study was to investigate the levels of heavy metals in water and bioaccumulation factor of heavy metals in selected fish species of River Gongola. Water and fish samples were collected monthly for 18 months (between December 2021 and May 2023) between the hours of 08:00am and 11:00am each sampling day. Heavy metals in the water and the fishes were analysed following standard procedure using Atomic Absorption Spectrophotometer. The results of the water analysis showed that Cadmium (Cd), Arsenic (As), Nickel (Ni) and Manganese (Mn) were above the recommended limit of WHO/NSDWQ. Significant differences were observed in metal concentration in the tissues (liver, muscle and gills) of the three fish species. The liver concentrated higher levels of the metals followed by the gills and the muscle. However, the levels of the metals reported in the tissues of the three fishes were below the recommended standards. The Bioaccumulation Factor (BAF) values calculated were mostly less than 1 showing no probability of bioaccumulation except for As in Bagrus bayad macropterus and Oreochromis niloticus and Iron (Fe) in B. bayad macropterus and Clarias gariepinus. Regular assessment and monitoring of the water and fish resources of this river is required to ensure safety of these products for consumer use.