Ichthyofaunal Diversity in the Jebba Lake Reservoir, Kwara State

Freshwater fish diversity in Nigerian reservoirs is under increasing pressure from overexploitation, habitat modification, and water quality degradation. This study assessed the ichthyofaunal composition, abundance, and diversity of the Jebba Lake Reservoir in Kwara State, North Central Nigeria. Fish were sampled over a period of five months using multi-mesh experimental gill nets, seine nets, and cast nets at six stations distributed across the reservoir. Specimens were identified using standard ichthyological keys, and community diversity indices including Shannon-Wiener diversity, Margalef richness, and Pielou evenness were calculated. Seasonal catch data were used to compute catch per unit effort for dominant species. A total of 51 fish species belonging to 22 families were recorded. Family Cichlidae had the highest species richness, followed by Characidae and Claridae. Oreochromis niloticus was the most abundant species across all stations, constituting 24 percent of total catch. Seasonal comparison revealed significantly higher diversity during the wet season, attributed to increased inundation of littoral zones. Catch per unit effort declined progressively toward the dam face stations, suggesting depth-related distribution patterns. Length-frequency analysis revealed that the majority of harvested Synodontis species were sub-adults, indicating recruitment pressure from intensive fishing. No exotic species were detected. The study provides updated ichthyological data for Jebba Lake and recommends seasonal size limits and habitat protection for littoral zones to ensure sustainable fisheries. Keywords: ichthyofauna, freshwater fish, Jebba Lake, diversity indices, Kwara State.