Investigating the Genetic Diversity of Clarias gariepinus Populations across Major River Systems in South South Nigeria

Understanding the genetic population structure of commercially exploited fish species is critical for both sustainable fisheries management and the development of selective breeding programmes. This study investigates the genetic diversity and population structure of Clarias gariepinus sampled from four major river systems in South South Nigeria, specifically the Imo, Cross, Benin, and Ethiope Rivers, using microsatellite DNA markers. A total of 240 fish, 60 per river, were sampled from artisanal fishers, and fin clips were preserved in 95% ethanol for molecular analysis. Eight polymorphic microsatellite loci were amplified by PCR, and allele scoring was performed using an automated fragment analyser. Population genetic parameters including allelic richness, observed and expected heterozygosity, inbreeding coefficient, and pairwise FST values were computed. Analysis of molecular variance was conducted to partition genetic variation within and among river system populations. Results revealed moderate to high genetic diversity within all four populations, with mean expected heterozygosity ranging from 0.61 to 0.74. Significant genetic differentiation was detected between the Imo and Cross River populations (FST = 0.087), while the Benin and Ethiope River populations showed minimal differentiation (FST = 0.012). Isolation-by-distance analysis was marginally significant across all populations. The study establishes baseline genetic diversity data for African catfish in South South Nigeria, providing essential information for establishing genetically diverse broodstock collections for the national catfish selective breeding programme under development at the National Institute for Freshwater Fisheries Research.

Keywords: genetic diversity, Clarias gariepinus, microsatellite, population structure, South South Nigeria