CONTRIBUTORY IMPACT OF SEWAGE ON POLLUTED OGUN AND LAGOS FISHING WATERS: INFLUENCE ON ANTIOXIDANT PROFILE AND PROXIMATE COMPOSITION OF SILVER CATFISH (Chrysichthys nigrodigitatus)

Abstract

Water pollution, a recurring phenomenon in fishing waters of industrial cities in Nigeria, inadvertently constitute hazards to the host biotic communities and the ecosystem. To continuously delineate the impacts of pollution via sewage outlets on aquatic life, this rainy season study investigated Chrysichthys nigrodigitatus, an aquatic food from Ogun River and Epe Lagoon, Nigeria, both of which are locally channeled for sewage release. Sixty (60) samples of C. nigrodigitatus were collected from six sites each representing a group (n=10), with mean weight and length of 762.20 ± 11.05 g and 42.21 ± 0.30 cm respectively. Ajegunle (control), Alaapa and Quarry (test sites) along the Ogun River course in Abeokuta; Ebute-Alashe (control), Oluwo and Marina (test sites) along the Epe Lagoon. Analysis of Biochemical Oxygen Demand and Chemical Oxygen Demand showed elevated variations at the sampled test sites than the control sites and above WHO safe limits. Significant (p < 0.05) increases in concentrations of heavy metals (lead, arsenic and cadmium) in the fishing waters from the sampled test locations particularly the Quarry and Marina sites, as well as in blood samples of fish, were observed when compared with their respective controls. Antioxidants profiling showed significant increases (p < 0.05) in superoxide dismutase and catalase activities in fishes from Alaapa (14- and 3- folds), Quarry (8- and 4- folds), Oluwo (9- and 3- folds) and Marina (8- and 3- folds) sites, while significant increases in glutathione-S-transferase activity were observed only in fishes from Quarry (5- fold) and Marina (4- fold) sites respectively. The glutathione concentration significantly decreased in fishes from all the test sites while malondialdehyde concentrations significantly increased in fishes from all the test sites compared with the respective controls. Proximate analysis of the fish samples showed significant increases (p < 0.05) in moisture and fiber contents, but significant decrease in fat, ash and protein contents compared with the respective controls. The results of the study showed that sewage pollution of fishing waters is hazardous to aquatic life as it induces oxidative stress and significantly reduces the nutritional value of the fishes obtained from such water bodies.