Assessment of Mormyridae species diversity and abundance in Ikere Gorge Dam, Oyo State, Nigeria

This study investigates the species composition, abundance, spatial distribution, seasonal variation, and diversity indices of the Mormyridae family in Ikere Gorge Dam, Oyo State, Nigeria. Field surveys were conducted across four major fishing sites; Spillway, Asamu, Agatu, and Irawote over a 24-month period. A total of 10 Mormyridae species belonging to seven genera were identified, with Petrocephalus bovei being the most numerically dominant (55.86%) and Mormyrus rume exhibiting the highest biomass contribution (43.68%). The Spillway station recorded the highest abundance and species richness, while Agatu had the lowest. Seasonal analysis revealed a clear pattern, with peak abundance occurring during the rainy season, particularly in September, which may be attributed to spawning migrations and increased availability of food resources. Diversity indices showed moderate species diversity, with a Shannon-Wiener index (H) ranging from 1.17 to 1.54 and an overall Simpson's diversity (1-D) of 0.74. Compared to other Nigerian inland waters, the Mormyridae diversity in Ikere Gorge Dam is relatively moderate, reflecting the ecological health and environmental dynamics of the reservoir. The findings underscore the importance of habitat-specific and seasonal management strategies to support the conservation of fish biodiversity and sustainable fisheries within the dam.