Evaluation of Heavy Metal Accumulation in Edible Fish Species from Artificially Polluted Ponds in Ogun State, South West Nigeria

Fish farming in peri-urban areas of Ogun State faces increasing contamination risk from industrial wastewater used for pond water supply in some localities. This study evaluated the accumulation of heavy metals including lead, cadmium, copper, zinc, and nickel in the muscle and liver tissues of Clarias gariepinus and Oreochromis niloticus raised in ponds supplied with water from an industrially contaminated stream in Ogun State. Fish samples were collected after twelve weeks of culture from contaminated and control ponds. Metal concentrations were determined by atomic absorption spectrophotometry following acid digestion. Bioaccumulation factors and health risk indices were calculated based on estimated weekly fish consumption rates in local communities. Results showed significantly higher metal concentrations in fish from contaminated ponds compared to control fish for all metals analysed. Liver tissues showed higher metal accumulation than muscle tissues, consistent with hepatic metal sequestration. Lead and cadmium in muscle tissue from contaminated ponds exceeded the European Union maximum limits for food fish. Estimated weekly intake of lead from consuming contaminated fish exceeded the provisional tolerable weekly intake threshold for regular consumers. The study concludes that industrial water use in aquaculture poses unacceptable human health risks and recommends mandatory water quality screening before pond water sourcing and regular metal monitoring of farmed fish in peri-urban areas of Ogun State. Keywords: heavy metals, fish accumulation, aquaculture, Ogun State, food safety.