Influence of Municipal and Abattoir Effluents on Surface Water Quality and Biological Responses of Fish in the Benue River, Nigeria

Abstract

This study assessed surface water quality and biological responses of fish exposed to municipal and abattoir effluents discharged into the Benue River at Makurdi, Benue State, Nigeria (Latitude 7.733218° N, Longitude 8.546908° E). Most physicochemical parameters, including temperature (27.59 ± 1.40°C) and pH (7.17 ± 0.10), fell within NESREA (2011) limits, but ammonia nitrogen (0.50 ± 0.12 mg/L) exceeded the 0.05 mg/L permissible limit, while biological oxygen demand (4.03 ± 0.13 mg/L) surpassed the 3.0 mg/L limit, alongside significantly elevated (p < 0.0001) dissolved oxygen, total alkalinity, total hardness, and transparency, reflecting abattoir-driven pollution. Among fish species, Clarias gariepinus recorded the highest gonadosomatic index but the lowest condition factor, while Oreochromis niloticus showed the highest hepatosomatic index and, with Coptodon zillii, higher condition factors (p < 0.05). Haematological analysis revealed depressed haemoglobin (9.20 g/dl) and markedly elevated white blood cell counts (8753.70 ×10⁹ cells/L; p < 0.001), indicating physiological stress. Liver enzymes (ALT, AST, ALP) and oxidative stress biomarkers (SOD, CAT, MDA, GPx, GR, LPO) varied significantly across seasons and species (p < 0.001), except glutathione (GSH), which remained stable. These findings confirm that abattoir and municipal waste degrade Benue River water quality and compromise fish physiological health, posing ecological and public health risks to communities dependent on the river.