Twenty eight adult Clarias gariepinus (mean weight 205 ± 12.89g SD; Mean length; 31.13 ± 3.82cm SD) were exposed to oilfield wastewater, oww (0. 10, 20, 30, 40, 50 and 60%) in quadruplicate for 28 days and the organs (plasma, gill, liver, kidney) and muscle were assayed for enzymes: aspartate transaminase (AST), alanine transaminase (ALT), acid phosphatase (ACP) alkaline phosphates (ALP) and lactate dehydrogenase (LDH). Changes in enzyme response were not concentration-dependent (P < 0.05), except ALP in kidney which showed a significant (p>0.05) increase with increased concentration of the oilfield wastewater when compared to the control. Other enzymes activities fluctuated around the control with LDH activity showing highest (2812.50±375.00 IU/L) response in all the organs. Lowest activity was recorded for ALT (4.00±0.00 IU/L) in the plasma. The changes observed can be used as an indicator of stress in C. gariepinus exposed to elevated levels of an oilfield wastewater. These changes can lead to death of fish and economic loss. The need therefore, for proper treatment of oilfield wastewater prior to discharge into the aquatic environment so as to reduce ecotoxicological problems and public health hazards is advocated.
Key words: Enzymes, oilfield wastewater, Clarias gariepinus, toxicity, aquatic environment
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