The population structure and genetic variability of North African catfish Clarias gariepinus (Burchell 1822) were investigated using partial mitochondrial DNA cytochrome b region sequences. Fifty-four (54) samples were investigated from three geographically isolated rivers in Nigeria. The analysis of 53 haplotypes revealed greater haplotype diversity (0.99930) and nucleotide diversity (p) (0.07270). According to an analysis of molecular variance (AMOVA), the genetic diversity of North African catfish within populations is significantly higher than the genetic diversity across populations. The FST scores (0.75000, 0.94792 and 0.95699) indicated that North African catfish populations in three Nigerian freshwater bodies had a strong genetic structure. The phylogenetic reconstruction of unique haplotypes revealed the placement of a haplotype (Ogbese) linked by others from all three groups with a point mutation ranging from 1 to 24 nucleotides. North African catfish populations in the Asejire and Ureje are genetically diverse, as evidenced by a high level of haplotype diversity of 1.0000, low nucleotide diversity spanning from 0.05101 to 0.07889, and high FST values (within-population genetic variation). The common haplotypes between some populations and mixes of haplotypes from different populations within the same genetic cluster demonstrate that the population genetic structure is not distinct.
