Proximate and mineral composition of Clarias gariepinus from the Khartoum Sewage Plant and Jebel Aulia Dam (White Nile), Sudan

Abstract

A comparative assessment of Clarias gariepinus from sewage-treated water and the White Nile was conducted. Moisture content showed no significant variation (p>0.05), but White Nile fish had slightly higher protein and ash levels(p<0.05). In contrast, sewage-exposed fish displayed increased lipid content, a higher caloric value, and an elevated lipid-to-protein ratio. Significant differences (p<0.05-p<0.001) in protein, lipid, and ash, respectively, indicated that sewage exposure alters chemical composition by enhancing lipid and mineral content. Heavy-metal analysis showed consistently higher concentrations in sewage-derived fish, with metals occurring in the order cadmium, iron, zinc, lead, nickel, and copper, compared with cadmium, iron, zinc, nickel, copper, and lead in White Nile samples. Cadmium, nickel, and lead differed significantly (p<0.05), and iron showed a highly significant increase (p<0.001), while copper and zinc remained similar. Metal levels in sewage samples exceeded FAO/WHO permissible limits, highlighting contamination risks and food-safety concerns.