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

Abstract

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.

Assessment of length-weight relationship and condition factor of Synodontics omias (Cuvier, 1816) in River Komadougou, Northeast, Nigeria

“…It was observed that some metric features were constant such as pelvic fin spine, dorsal fin spine while others varied. The finding was in line with the work of Mohamed (2010) who recorded similar metric features with S. schall and S. serrate. The variation observed in this study when compared with other species might be related to environmental variations such as water temperature, stress, food availability, spawning ground and sex.…”

“…The morphometric (total length, standard length, body depth, head length, head depth, snout length, dorsal fin length, anal fin length, eye diameter, body weight, caudal peduncle length, caudal peduncle depth, caudal peduncle depth, pelvic fin length) features of S. omais were within the range reported by Famoofo and Abdul (2020) from Iwopin freshwater ecotype of Lekki Lagoon, Ogun State, Nigeria who worked on S. nigrita. The result from morphometric characteristics was also found to be similar to the study of Mohamed (2010) who studied the characteristics of two Synodontis species in the White Nile and Lake Nubia in Sudan. The meristic (dorsal fin ray, anal fin ray, pectoral fin ray, caudal fin ray, pelvic fin ray, pelvic fin spine, dorsal fin spine and gill rakers) features which are countable features are also used for fish identification.…”

“…Also, Midhat et al (2012) reported a similar result in her study on S. schall in River Nile, Egypt. Negative allometric growth pattern was also reported by Lalèyè et al (2006) in their study of two Synodontis spp (S. schall and S. nigrita; ) in Ouémé River, Benin; Hassan (2007) in his study of S. schall in River Nile, Egypt, Akombo et al (2011) in their study of four Synodontis species from Lower Benue River, Makurdi, Nigeria; and Famoofo and Abdul (2020) in their study in fresh-water ecotype of Lekki Lagoon, Ogun State, Nigeria while Mohamed (2010) reported positive allometric growth pattern for S. schall and S. serrata in Lake Nubia, while S. schall and S. serrata from White Nile shows both allometric (Males) and isometric (female) growth pattern. According to Enin (1994), who stated that whenever b-value indicates allometric growth caution must be applied because of violation of the assumption of isometry in the model.…”

From taxonomic deflation to newly detected cryptic species: Hidden diversity in a widespread African squeaker catfish

“…Synodontis schall is traditionally considered widespread throughout the Nilo-Sudanian ichthyological province from the Atlantic to Indian Ocean 17 . Its widespread distribution, abundance and easy harvesting make it one of the most important subsistence fish species in Sub-Saharan Africa north of equator and along the whole Nile valley 28,32–34 . Importantly, this ecologically plastic species 28 is less likely to be affected by climatic changes and anthropogenic drainage alterations, making it a prospective source for fisheries in the future 35 .…”