This research was carried out to examine the distribution of enzymatic activities of some tissues (liver, muscles and gills) of selected aquatic organisms (Nile tilapia, Mullet fish and Crab) collected from some crude oil polluted rivers (Abuloma Jetty and Woji Jetty) and Ojimba-ama a non-oil polluted area which served as control. The aquatic organisms were obtained from rivers which are used as jetty for transportation of petroleum products and other industrial activities like welding, dredging, refuse dump, etc. Enzyme activities of fish and crab tissues (liver, muscles and gills) were measured for some biomarker enzymes such as catalase, rhodanase and glutathione S-transferase. Results were shown in means of triplicate values which were subjected to statistical analysis using analysis of variance (ANOVA). Enzyme activity in Nile tilapia across the three locations ranged from 44.39±0.01 μ/mgprotein to 171.45±0.01 μ/mgprotein with GST in gills having the lowest value and rhodanase in the liver recording the highest value. Enzyme activity in Mullet across the three locations ranged from 18.58±0.10 μ/mgprotein to 120.37±0.02 μ/mgprotein with catalase in muscles having the lowest value and rhodanase in the liver recording the highest value.  Enzyme activity in Crab across the three locations ranged from 40.79±0.03 μ/mgprotein to 130.72±0.01 μ/mgprotein with GST in gills having the lowest value and rhodanase in the liver recording the highest value.  Rhodanase showed the highest level of enzyme activity in all the tissues. Liver recorded the highest enzyme activity across all samples from the three locations which may be as a result of the liver being the principal detoxification organ for xenobiotic substances. From this study, there was an increase in the enzyme activities of the biomarkers across all the tissues which indicate a contamination from pollutants capable of causing oxidative stress in the organisms.

In this study, the level of polycyclic aromatic hydrocarbons and heavy metals (Pb, Cr, Zn, Cd, Cu, Fe and Mn) contamination were determined in Nile tilapia, Mullet fish and Crab collected from crude oil polluted rivers (Abuloma and Woji Jetty). Average individual PAHs concentration ranged from 0.0001mgkg-1 to 11.22±0.02mgkg-1 in Nile tilapia, 0.0001mgkg-1 to 13.43±0.17mgkg-1 in mullet fish and 0.0001mgkg-1 to 12.23±0.06mgkg-1 in crab. Benzo[a]pyrene (a carcinogenic PAH) concentrations detected in fish and seafood in this study exceeded the acceptable limit set by the European Commission (0.002mgkg-1) for fish considered safe for human consumption. The levels of Pb and Cr in fish and seafood were found to have remarkably higher concentrations which exceeded the acceptable levels (FAO/WHO) in food sources for human consumptionand that of Cd, Fe, Zn, Cu and Mn were lower. Results from this study revealed high levels of PAHs and heavy metals in seafood samples from all study locations. These high PAHs levels in these commonly consumed seafoods from the rivers question their safety for human consumption.