The effect of copper on the blood chemistry of Clarias gariepinus (clariidae) Original Research Article

Environmental stressors, both natural and humanly induced, could cause changes in cellular function which alter the physiology of organ systems in fish. The need to comprehend and predict the condition which stress metals will pose on fish, and extrapolate the effect of pollutants from laboratory to population levels, have forced scientists to search for physiological and biochemical indicators of health and sublethal toxicant effects. Hematological evaluation of fish blood provides valuable facts concerning the physiological response of fish to changes in the external environment. Furthermore, hematological variables are well known for their clinical value in prognosis and diagnosis. Sublethal responses after exposure to toxicants can be determined by commonly applied techniques. Measurements for a number of hematological and carbohydrate metabolic variables were recorded at winter and summer temperatures after fish, acclimated for 3 months to experimental conditions, were exposed to sublethal concentrations of copper for 96 hr in a continuous-flow experimental system. Controls were run at the same time to establish essential baseline hematological values. Fish were exposed to the mean copper concentration as was found in the Olifants River, Kruger National Park, during summer (0.05 ± 0.032 mg liter−1) and winter (0.085 ± 0.032 mg liter−1) to establish the effect thereof on the variables mentioned. The results proved that the concentration of copper in the river exerts a physiological effect on Clarias gariepinus at 21 ± 1 and 28 ± 1°C which manifests in changed blood chemistry. Pathological conditions, such as erythrocytopenia, leucocytosis, hyperglycemia, and hyperprotonemia, are evident. The fish physiologically adapted to the environmental change, which does not necessarily reflect a state of normality.