Impact of Oil Pollution on Fish Diversity and Abundance in the Nun River, Bayelsa State

Oil pollution from pipeline leaks and illegal refining activities has severely degraded aquatic habitats in the Niger Delta, with documented impacts on fish populations in major river systems. This study investigates the impact of oil pollution on fish species diversity and abundance in the Nun River, Bayelsa State, South South Nigeria, using an upstream-downstream comparative design. Fish samples were collected from three stations using multi-mesh gillnets, cast nets, and fish traps over four months. Surface water and sediment samples were collected concurrently for total petroleum hydrocarbon analysis. Fish species richness, Shannon-Wiener diversity index, evenness, and dominance were computed for each station. A total of 31 fish species were recorded at the upstream reference station compared to 14 and 11 at the two downstream stations located near identified oil spill sites. Total petroleum hydrocarbon concentrations in surface water exceeded the DPR environmental guidelines at both downstream stations. Shannon-Wiener diversity indices were significantly lower at polluted stations, and dominance was higher, indicating community simplification. Pollution-tolerant species such as Tilapia zillii and Clarias spp. dominated catches at impacted stations, displacing commercially valuable species. The study provides empirical documentation of oil pollution-driven fish community degradation in the Nun River and calls for accelerated remediation of identified spill sites as a prerequisite for fisheries recovery in this ecologically sensitive waterway.

Keywords: oil pollution, fish diversity, Nun River, Niger Delta, total petroleum hydrocarbons