Diversity of the freshwater fishes of Sudan is related to diversification of the aquatic habitats which ranges from slow to fast flowing, and from muddy, sandy to rocky banks with varying densities of hydrophytes. In some instances this diversity is due to deliberate introduction of exogenous species such as Oreochromis macrochir (Family: Cichlidae); Ctenopharyngodon idella (Family: Cyprinidae); Oncorhychnus mykiss (Family: Salmonidae) into parts of the Nile system or   introduction of Gambusia affins (Family: Poeciliidae) and Cyprinus carpio (Family: Cyprinidae) in the canalization system [1]. Identification guides for freshwater fishes of Sudan were made by Sandon, Abu Gideiri [2], Bailey [3]. Neumann et al. [9] published an annotated checklist for fishes of the Nile in Sudan and Egypt. They gave a scholarly detailed account on species distribution in the Nile and its tributaries. They rigorously discussed and summarised the conservation status of fish species with respect to regionally extirpated or threatened at type locality, deficient and/or not evaluated data. Specific studies on their distribution on the White Nile from the vicinity of Jebel Aulia Dam were due to Adam [4], Hamza [5] and Abdel-Rahman [6]; at Jelhack area by Mosa et al. [7] and Moritz et al. [8] from Aba Island (13° 15’N) through Kosti to Makhaleif (12° 5’N).

The objective of this work was to document freshwater fish species collected during eight field trips from 2002 to 2019 from Kosti area, White Nile.

The Study Area

According to Neumann et al. [9] the White Nile at the study area (Kosti) is slowly flowing, and is 1.5-2km wide with hard substrates on the riverbed and rocky outcrops north of Kosti. The area is relatively rich in hydrophytes such as Water lily (lotus), papyrus (Cyperus papyrus) with aggregations of the invasive common water hyacinth (Eichhornia crassipes). The water hyacinth was incriminated for changing the composition of the fish fauna. Their sporadic dense stands make it difficult for fishers to sail their canoes from or to the landing sites (Figure 1-2). Some fishers claimed that it wraps around propellers and poles, provides a hiding place for snakes and crocodiles. Nile oyster were abundant, turtles (Trionyx triunguis) and small Nile monitors (Varanus niloticus) were rarely seen in the catch but their remains were seen in fish camps on Aba Island.

Fish Collection

Fish specimens were collected from commercial fishers operating around Kosti to supply the major fish landing sites and the fish market at Kosti. Experimental fishing was infrequently made around Kosti (along the main White Nile course and southern extremities of Abba Island) using gill nets, cast nets and fish cages to supplement the data.

Identification of collected specimens was based on Abu Gideiri [2] and Bailey [3]. Nomenclature followed those accepted as valid names by Froese and Pauly [10].

Figure 1: Fish Canoes

Figure 2: Fish Landing Site Note Hydrophytes

The freshwater fish species identified from collection made around Kosti during eight field studies over 15 years were given in Table 1.

The Table 1 showed the presence of 64 species, falling into 37 genera and 20 families. Thirty five fish species belonging to 16 families were collected throughout the study. Four species showed 88% occurrence, while five Mormyrids species were only encountered during December 2018.  Neumann et al. [9] recorded from the White Nile at Kosti 57 species, 36 genera and 20 families. Khalid and Elawad [11] in their unpublished technical report on fish species of Musran Island recorded 38 species belonging to 27 genera and 14 families.

According to Abu Gediri [8] M. anguilloides, H. bidorsalis and S. batensoda occurs in the White Nile in the vicinity of Khartoum; C. citharinus and C. latus inhibits the main Nile and Baher el Gabel and H. longifilis occurs in the main Nile north of Khartoum. The occurrence of all these species in Kosti area was confirmed during this study indicating. One family Protopteridae and 20 species encountered in this study were not reported by Neumann et al. [9]. On the other hand, families Nothobranchiidae and Eleotridae, and 13 species recorded by Neumann et al. [9] were not encountered during this study. These were Polypterus endlicherii, Chelaethiops bibie, Leptocypris niloticus, Distichodus nefasch, Micrelestes elongates, Siluranodon auritus, Synodontis cuadovittatus, Synodontis frontosus, Synodontis khartoumensis, Epiplatys bifasciatus, Epip latys spilargyreius, Kribia nana and Hemichromis letourneuxi. The fish species which are in common with Neumann et al. [9] were 41 (Table 1). Mouso et al. reported from Jelhak (400 Km south of Kosti) 56 species, 35 genera and 20 families. Moromyrops cyprnoides. Synodontis filamentosus, Synodontis frontosus, Synodontis eupterus, Synodontis vittatus and Synodontis khartoumensis recorded by Khalid and Elawad [11] were not found during this study.  The 25 fish species not reported by Khalid and Elawad [11] were marked as (#) in Table 1.

The combined White Nile fish species recorded by Abu Gideiri [2] and Bailey [3] fall into 97 species, 45 genera and 23 families. Labeo latebra was reported as a new species to science from Kosti, Sudan by Moritz and Neumann [12]. The distichodontid Paradistichodus dimidiatus was reported from Kosti by Blažek et al. [13]. Its presence in the same area together with the cyprinid Enteromius macrops were reported as first record for the Main Nile Basin by Moritz et al. [8]. Moritz et al. [8] during a survey from Aba Island to Makhale if added and confirmed 11 species to the White Nile. These were Petrocephalus keatingii, Pollimyrus petherici, Neolebias unifasciatus, Enteromius werneri, E. stigmatopygus, E. perince, Cyphomyrus petherici, Mochokus brevis and Clarias engelseni. They also mentioned an apparently undescribed Haplochromis sp. and Sarotherodon sp. Out of these, only B. niger and C. engelseni were encountered during this study. Combining the findings of the present study (64 species), with those of Neumann et al [9] not reported in this study (13 species) and those of Moritz et al [8] not reported in this study (11 species) yielded 88 fish species in Kosti area which constituted 91% of the 97 fish species recorded from the whole stretch of the White Nile by Abu Gideiri [2] and Bailey [3]. The richness of Kosti area in fish species is probably due to diversification of its habitat.

Table 1. Freshwater Fishes from Around Kosti

Table 1: Continue

*not encountered by Neumann et al. [9].  #not encountered by Khalid and Elawad [11]. 

It follows from the above that there is a need to update the locality records through long-term systematic surveys using traditional gears, dip nets and electro-fishing methods. Comparison of the fish species in Sudan with those found in freshwater masses in adjacent countries, to work out their phylogenic relationships is also an area of research that should be given due attention.

Ethical Issues

Ethical issues pertaining to approval and consent to participate, human and animal rights, consent for publication, availability of data and materials are Not Applicable. The authors declared no conflict of interest financial or otherwise.

Funding

The Ministry of Higher Education and Scientific Research partially funded this work.

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