Integrated Assessment of Genetic Diversity and Reproductive Potentials in African Catfish (Clarias gariepinus; Burchell, 1822) from River Benue, Nigeria

Abstract

Genetic diversity and reproductive performance are important determinants of the sustainability of wild fish populations and the selection of suitable broodstock for aquaculture. This study evaluated the genetic diversity, morphometric characteristics, and reproductive potential of Clarias gariepinus from the Upper, Middle, and Lower sections of River Benue in Taraba State, Nigeria. Sixty (60) sexually mature specimens (20 per sampling location) were collected between March and May 2026. Morphometric measurements, gonadosomatic index (GSI), absolute and relative fecundity, and egg diameter were determined using standard procedures. Genetic diversity and population relationships were assessed using mitochondrial 16S rRNA sequences, haplotype diversity, nucleotide diversity, phylogenetic analysis, and haplotype network reconstruction.  Fish from the Lower Benue exhibited the highest mean total length (45.72 ± 3.98 cm) and body weight (1,276.84 ± 210.31 g). Female GSI was highest in the Lower Benue population (10.54 ± 1.06%), compared with the Middle (9.68 ± 0.92%) and Upper (8.47 ± 0.88%) populations. Absolute fecundity followed a similar pattern, with the highest value recorded in the Lower Benue (85,230 ± 6,980 eggs) and the lowest in the Upper Benue (70,350 ± 5,720 eggs). Female body weight was strongly positively correlated with absolute fecundity (r = 0.81, p < 0.01). Analysis of mitochondrial DNA sequences identified six unique haplotypes (H1 - H6), with frequencies of 28, 9, 7, 6, 5, and 5 individuals, respectively among the 60 Clarias gariepinus specimens sampled from the Upper, Middle, and Lower Benue populations, with haplotype diversity ranging from 0.76 to 0.84 and nucleotide diversity from 0.0036 to 0.0052. Phylogenetic clustering and the distribution of shared haplotypes suggested genetic relatedness among the sampled populations. These findings indicate spatial variation in morphometric characteristics and reproductive performance, alongside moderate to high mitochondrial genetic diversity in the sampled populations. The results provide preliminary evidence to support broodstock selection and the conservation of genetic resources of C. gariepinus in River Benue.