A Comparison of Pollution Status and Fish Assemblage of River-Nun and Ekole River, Bayelsa State, Nigeria

The relationship between pollution status of water bodies and fish assemblage was investigated for Ekole river and River-nun respectively in the Niger Delta, Nigeria. This was done to gauge the pollution status of these important rivers and the effect it has on fish assemblage patterns. This is critical to forestall further pollution and safeguard food security. Sampling was done monthly for one year for physicochemical analysis from three sampling points on the two rivers respectively. Physicochemical samples were analyzed for Dissolved oxygen (DO), Biochemical oxygen demand (BOD5), Temperature, Alkalinity, Electrical conductivity (EC) and pH. Fish samples were also collected monthly from fish landing points from fishers, counted and identified using standard keys. Result show that all physicochemical parameters of the two rivers were within the international permissible limit in both river systems. Fish data show that Ekole River with 20 families (29 species) has a greater species diversity than River-Nun with 18 families (27 species). Ekole River with 12,406 individuals also has a greater species abundance than River-Nun with 12,399. The distribution and abundance of fish in Ekole river show that the wet season (6,740) has a greater species abundance than the dry (5,666) season. While in River-Nun the wet season (6,860) has a greater species abundance than the dry season (5,539). The families Cichlidae, Claridae, and Cyprinidae were the most dominant family in both river bodies. The Similarity/dissimilarity indices of Ekole and River-Nun reveal a Bray-Curtis dissimilarity complex of 0.101 (Very similar), Dice-Sorensen Similarity Index of 0.964 (Very similar) and Jaccard Index / Similarity Coefficient of 0.9 or 90% (Very similar). Based on the findings of this study, the water bodies are not under any immediate threat of pollution and the two river bodies have similar fish composition. It can be concluded that river systems with similar water quality characteristics do have similar fish assemblage patterns.