Persistence of pollution into our natural environment has concurrently led to instability, disorder, harm or discomfort to both the physical systems and living organisms inhabiting the ecosystem. Potentially harmful substances such as pesticides, heavy metals, paper mill waste, polychlorinated biphenyl and crude oil are often released into the aquatic environment. When large quantities of these pollutants are released there may be an acute impact as measured by large-scale sudden mortalities of aquatic organisms such as fish kills. Lower levels of discharge may result in an accumulation of the pollutants in body composition of fish. The effects of water pollution on fish species can be classified into acute effects and long term chronic effects, which includes immune-suppression, reduced metabolism, and damage to gills and epithelia. Pollution-related diseases include fin/tail rot, gill disease, hepatic damage and ulceration. Specific examples of fish diseases that reflect the effects of pollution include, fin and tail rot caused by Amnonas hydrophila and Pseudomonas jluorescens. The polluted water may have undesirable colour, odour, taste, turbidity, harmful chemical contents, toxic and heavy metals, pesticides, industrial waste products, domestic sewage, virus, bacteria, protozoa and worms. Fish species are not only tolerant to severe contaminated waters but show a variety of specific morphological deformities and lesions that appear to reflect the level of water pollution. Assessing morphological deformities is one of the most straightforward methods to study the effects of contamination on fish because of the ease of recognition and examination when compared with other types of biomarkers. The indiscriminate disposal of pollutants without pre-treatment should be discouraged. In order to avoid the effects of water pollution on fish health, effluents discharged from industries and other sources should be properly treated.

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This study investigated the effect of varying levels of Gongronema latifolia on growth, nutrient utilization, biochemical and hematological parameters of Clarias gariepinus juveniles. One hundred and five (105) juveniles were equally distributed in fifteen plastics tanks and each triplicated. Three inclusion levels of the plant extract (150mg/kg, 300mg/kg and 500mg/kg) were prepared, while the antibiotics served as negative control and the diet without any inclusion served as the positive control. The fish meal was supplemented with Gongronema latifolia (benth) extract and the control diets were fed to satisfaction, while the tank water was changed every other day. The weight gained and feed intakes of the fish were determined at the end of every week and the growth parameters were evaluated. Growth parameters showed that the highest value was recorded in treatment 4 (300mg) 226.07±9.96 for the final weight gained, while the lowest was observed in treatment 5(500mg) was 165.47±31.55. Supplementation of fish feed on Gongronema latifolia did not cause any adverse effects on biomarkers of liver toxicity and oxidative stress. Monocytes and lymphocytes concentration were significantly reduced with no alteration in red blood cell count and hemoglobin concentration. This study showed that the supplementation of Clarias gariepinus juvenile diet with G. latifolia extract promoted growth and weight gain in the fish stock with no toxic effect on the liver and oxidative stress.