Heavy Metal Accumulation in Tissues of Catfish (Clarias gariepinus) from Irrigation Channels in Sokoto State

Aquaculture and wild catfish harvested from irrigation water channels in Northern Nigeria are a primary protein source for local communities. The potential accumulation of heavy metals in fish tissues from agricultural irrigation runoff poses significant food safety risks. This study assessed the bioaccumulation of lead, cadmium, zinc, iron, and chromium in muscle, liver, and gill tissues of Clarias gariepinus collected from three irrigation channels in Sokoto State, North West Nigeria. Fish specimens were collected monthly over four months and subjected to acid digestion prior to analysis by atomic absorption spectrophotometry. Metal concentrations were compared against WHO and FEPA permissible limits for fish intended for human consumption. Irrigation water and sediment samples were also analysed to determine the source of contamination. Results showed highest metal concentrations in liver tissues compared to muscle and gills, consistent with the liver's role in detoxification. Cadmium and lead concentrations in liver exceeded WHO permissible limits at two of three sites. Fish from the channel nearest to an industrial market recorded the highest tissue cadmium levels. Bioaccumulation factors indicated significant transfer of zinc and iron from water to fish tissues. Muscle samples were within acceptable limits for all metals at the least impacted site. The study calls for monitoring of irrigation water metal content and fish tissue quality standards to protect food safety in Sokoto's farming communities. Keywords: heavy metals, Clarias gariepinus, bioaccumulation, irrigation channels, Sokoto State.