Climate Change Vulnerability Assessment of Freshwater Fish Biodiversity in the River Benue Basin, North Central Nigeria

Freshwater fish in the River Benue basin face compounding threats from climate change-driven alterations in river hydrology, temperature, and seasonal flood pulses, yet quantitative vulnerability assessments for this biodiversity are absent in the literature. This study applied a trait-based climate change vulnerability assessment framework to thirty-four fish species recorded in the River Benue basin, spanning North Central and North East Nigeria. Exposure, sensitivity, and adaptive capacity scores were derived from species distribution data, biological traits including thermal tolerance, reproduction strategy, and mobility, and projected hydrological change scenarios under RCP 4.5 and RCP 8.5 climate pathways. A composite vulnerability index was calculated and species were categorised into vulnerability classes. Results showed that eight species fell into the high to very high vulnerability category, predominantly benthic and habitat-specialist species with narrow thermal ranges and limited dispersal ability. Pelagic migratory species showed lower vulnerability due to higher adaptive capacity. Projected river flow reductions under RCP 8.5 imposed significantly higher exposure scores than temperature changes alone, highlighting hydrological change as the primary climate threat to fish biodiversity in the basin. The study identifies the most climate-vulnerable fish species for priority monitoring and recommends that the Nigerian Fisheries Agency integrate climate vulnerability assessments into fisheries conservation planning for the River Benue system. Keywords: climate vulnerability, freshwater fish, River Benue, biodiversity, North Central Nigeria.