Spatio-Temporal Assessment of Ichthyofaunal Diversity and Structure of Ikere Gorge Lake, South-West Nigeria

Abstract

Freshwater reservoirs play vital ecological and socio-economic roles as habitats for diverse fish species and as sources of food security and livelihoods. This study assessed the spatio-temporal distribution of fish families in Ikere Gorge Lake, a reservoir on the Ogun River, Southwestern Nigeria, to provide baseline information for sustainable fisheries management. Experimental gillnets of graded mesh sizes were deployed across three habitat strata (shore, surface, and bottom) in both wet and dry seasons. A total of 12 fish families comprising representatives of Cichlidae, Claridae, Characidae, Bagridae, Mormyridae, Schilbeidae, Mochokidae, Centropomidae, Cyprinidae, Channidae, Hepsetidae, and others were recorded. Cichlidae dominated numerically across seasons, reflecting their ecological adaptability and reproductive advantage, while Mormyridae and Centropomidae contributed significantly to biomass, particularly during the dry season. Seasonal variations in abundance were observed, with higher species representation during the wet season, consistent with rainfall-driven hydrological fluctuations and spawning patterns. The spatial distribution revealed benthic families such as Mochokidae and Claridae were more prevalent in bottom habitats, whereas pelagic taxa like Characidae and Schilbeidae were more common in surface waters. These findings align with previous reports of ichthyofaunal patterns in Nigerian inland waters (Ayoade, 2011; Omoniyi and Agbon, 2021) and highlight the importance of long-term ecological monitoring. The study concludes that while Ikere Gorge Lake sustains a relatively diverse fish community, inter-annual and seasonal variations underline the need for adaptive management strategies to balance exploitation with conservation.