Diversity and Abundance of Freshwater Fish Species in the Anambra River, South East Nigeria

This study investigates the diversity and abundance of freshwater fish species in the Anambra River, located in Anambra State within Nigeria's South East geopolitical zone. The Anambra River supports artisanal fisheries that provide food security and livelihoods for riparian communities, yet baseline data on fish species composition are limited. Using a descriptive survey design, fish samples were collected monthly over six months from five stations along the river using gill nets, cast nets, and traps. Species were identified morphologically, diversity indices including Shannon-Wiener, Margalef, and Pielou evenness were calculated, and relative abundance was determined for each species. Physicochemical parameters including dissolved oxygen, temperature, pH, conductivity, and turbidity were measured concurrently at each station. A total of 28 fish species belonging to 16 families were recorded, with Cichlidae and Mormyridae as the most species-rich families. Tilapia zillii and Synodontis clarias were the most abundant species across stations. Shannon diversity was highest at the upstream station and lowest near the heavily fished midstream section. Dissolved oxygen and turbidity showed significant correlations with species abundance distribution. Fishing pressure and upstream agricultural runoff were identified as primary threats. The study provides baseline species diversity data essential for fisheries management planning in the Anambra River basin and recommends seasonal fishing restrictions and regulation of upstream agrochemical use to sustain fish diversity. Keywords: fish diversity, Anambra River, freshwater fisheries, Shannon index, South East Nigeria.