Genetic Diversity Analysis of Clarias gariepinus Populations Across Major Nigerian River Basins

This study analysed the genetic diversity and population structure of Clarias gariepinus (African catfish) sampled from five major river basins in Nigeria, spanning the Niger, Benue, Cross, Anambra, and Sokoto basins, to inform aquaculture broodstock management and conservation planning. Understanding the genetic diversity and differentiation of C. gariepinus populations is essential for preventing inbreeding depression in captive stocks and protecting wild genetic reservoirs. Tissue samples were collected from 200 individuals, 40 per basin, and microsatellite genotyping was performed using eight polymorphic microsatellite loci. Measures of genetic diversity including observed heterozygosity, expected heterozygosity, allelic richness, and inbreeding coefficient were computed. Population differentiation was assessed using Fst statistics and Bayesian clustering in STRUCTURE software. Results showed moderate overall genetic diversity, with mean observed heterozygosity ranging from 0.52 to 0.69 across basins. The Cross River basin population exhibited the highest allelic richness, while the Sokoto basin population showed the lowest diversity, potentially reflecting geographical isolation and reduced gene flow. Bayesian clustering identified three distinct genetic clusters broadly corresponding to south-southern, north-central, and north-western basin groups. Pairwise Fst values were highest between the Sokoto and Cross basin populations, confirming significant genetic differentiation. Evidence of recent bottlenecks was detected in two basin populations. The study recommends that broodstock for aquaculture hatcheries be sourced from genetically diverse and locally representative wild populations, and that genetic monitoring programmes be established to track diversity trends in exploited C. gariepinus populations across Nigerian river basins. Keywords: genetic diversity, Clarias gariepinus, microsatellite, population structure, Nigerian rivers