Characterization of two Synodontis (Siluriformes: Mochokidae) catfish species in the White Nile and Lake Nubia

I found that cluster analysis of body weight, 25 morphometric measurements and seven meristic counts separated most of the population of Synodontis schall, from the Jebel Aulia area, Khartoum along the White Nile, from the population of Lake Nubia, the southern part of a large reservoir on the River Nile at the northern borders of the Sudan, above the Aswan High Dam in Egypt. Analysis of variance revealed significantly higher mean numbers of gill rakers and mandibular teeth in Lake Nubia for S. schall and S. serrata, compared to the two species in the White Nile. Higher numbers of anal fin rays were also found in S. serratus from Lake Nubia compared to the White Nile. Females of both species exhibited isometric growth in the White Nile and allometric growth in Lake Nubia. Females of S. schall and both sexes of S. serrata in Lake Nubia had higher condition factors compared to individuals in the White Nile. I detected differences in allele frequency of nine out of 17 loci between the populations of the two localities. The average heterozygosity values were lower for the two species from Lake Nubia compared to both species in the White Nile. The inter-population genetic distance was 0.02 for both species. This study should be applied to other species in Lake Nubia for rational fishery management and aquaculture.