Heavy metal concentrations in tissues of commercially exploited fish (Oreochromis niloticus baringoensis, Protopterus aethiopicus, Clarias gariepinus) from Lake Baringo, Kenya

Abstract

Studies have shown that elevated heavy metal concentrations in water and sediments may be biomagnified along the aquatic food chains/webs and eventually affecting human health through the consumption of metal-contaminated water and/or fish from such water bodies. This study was conducted to assess the concentration of heavy metals in the tissues of Oreochromis niloticus baringoensis, Protopterus aethiopicus and Clarias gariepinus fish species of Lake Baringo and compare the results with WHO guideline values. Water and fish samples were collected from five selected sites in six sampling occasions and the analyses for heavy metals (i.e. Cu, Hg, Cd, Pb) in fish and water samples was done using the Atomic Absorption Spectrophotometer at Nakuru Water and Sewerage Company Laboratory. There was a significant difference in physical chemical parameters from all sites in Lake Baringo except for temperature. Copper, Cadmium and mercury were available in measurable quantities in water samples but lead was below detection limit (<0.026). There was no significant difference in heavy metal concentration in all the tilapia (F=0.88, P=0.44), lungfish (F=0.99, P=0.43) and catfish (F=0.09, P=0.70) samples collected from different sampling sites. The pooled heavy metal concentration levels recorded in fish for Copper, Cadmium and Zinc was 0.473±0.125, 3.565±0.063 and 24.398±3.262 respectively. Therefore the heavy metal concentration in fish decreased in the sequence Zinc>Cadmium>copper. Lead and Mercury concentrations in fish samples were below the limits of instrument detection. Copper, Lead and Mercury concentration in fish were below WHO guideline values thus posing more of an environmental than human health concern. However, Cadmium and Zinc concentration was above WHO guideline values thus posing a human health concern. Regular monitoring of the Lake Baringo water quality is therefore necessary to record any variation in the water quality and heavy metal concentration in fish in order to curb heavy-metal related health effects arising from consumption of heavy metal contaminated fish.