Assessment of genetic variations of Nile Tilapia (Oreochromis niloticus L.) in the Volta Lake of Ghana using microsatellite markers

Abstract

A study was conducted to investigate genetic diversity and population structure among populations of Nile tilapia Oreochromis niloticus (Cichlidae) in the Volta Lake of Ghana using microsatellite markers. Four hundred (400) fish specimens were obtained from nine naturally occurring subpopulations and one selectively bred strain, ‘Akosombo strain’. These were characterized using 15 microsatellite loci. Twelve of the loci were multi-allelic, producing 2 to 11 alleles per locus while the effective number of expected alleles (Ne) ranged from 2.030 to 2.855. The observed heterozygosity (Ho) and expected heterozygosity (He) were high ranging between 0.488 - 0.594 and 0.424 – 0.502, respectively. The Kpando-Toko populations had the highest variability (He = 0.502) whilst the Buipe population had the least variability (He = 0.424). Gene diversity based on locus ranged between 0.1638 and 0.8673 whilst the genetic differentiation between populations (FST) was 0.074 indicating moderate differentiation between the populations. However, there was very high genetic variation (93%) within individuals. Nei’s distance between the populations ranged between 0.011.and 0.133, whilst estimated overall gene flow (Nm) and Shannon Information Index were 8.265 and 0.822 respectively. The 10 populations studied formed two main clusters with the longest pairwise Nei’s genetic distance of 0.133 between the Dzemeni and Kete-Krachi populations.