Pollution of Nigerian Aquatic Ecosystems by Industrial Effluents: Effects on Fish Productivity

Nigeria is uniquely endowed with vast water resources. The near-shore, estuaries, rivers, lakes and pond all taken together, offer tremendous opportunities for fish production. Globally, water bodies are primary means for disposal of waste especially the effluents from industrial, municipal, sewage and agricultural practices near the water body. Studies carried out in most cities in Nigeria has shown that industrial effluent is one of the main sources of water pollution in Nigeria and less than 10% of industries in Nigeria treat their effluents before discharging them into the water bodies. This effluent can alter the physical, chemical and biological nature of the receiving water body resulting in the death of the inhabiting organisms including fish. Untreated industrial waste discharged into water bodies have resulted in eutrophication of aquatic ecosystem as evidence by substantial algal bloom leading to dissolve oxygen depletion and eventually massive mortality of fish and other organisms. Industries like textile producing factory, paper manufacturing plants, oil refinery, brewery and fermentation factory and metal producing industries discharge their wastes into the aquatic ecosystem. These industrial wastes contain pollutants like acids, heavy metals, oil, cyanide, organic chemicals, pesticides, polychlorinated biphenyls, dioxins etc. Some of these pollutants are carcinogenic, mutagenic and teratogenic while some are poisonous depending on the level of exposure and intake by aquatic organisms and man. These pollutants affect the biological growth and reproduction of fishes in the aquatic ecosystem thereby reducing the amount of captured fishes. Fish and other aquatic lives face total extinction due to destruction of aquatic lives and natural habitats by pollution of water bodies. Effluents and wastes produced by industries should be minimised by using low and non-waste technologies; and effluents should be properly treated before they are discharged into aquatic environment.