SANBI

Rationale (Changed due to Same category and criteria)

This species is widespread in the Orange-Vaal River System, South Africa’s largest river system, and is also found in several other large river systems, e.g. Gourits in the Western Cape Province, and in several systems in the Eastern Cape (e.g. Gamtoos). Although there is concern about water quality in several tributaries of the Vaal River, especially in Gauteng Province, the species remains widespread and common across the six river systems in which it occurs naturally and is therefore assessed as Least Concern.

Distribution

The species is relatively widespread geographically in South Africa, occurring in the Orange-Vaal, Gourits, Gamtoos, Sundays, Bushmans, Great Fish, Keiskamma, Buffalo and Nahoon Rivers, and also the Orange River system in Lesotho and Namibia (Skelton 2001, Ramoejane 2016). It appears to be uncommon in the lower Orange River, and was not recorded by Naesje et al. (2007) during detailed fish surveys there. It is suspected to have been translocated to the Keiskamma, Buffalo and Nahoon River systems in the Eastern Cape Province (Skelton 2001, Ramoejane 2016) and to the Olifants catchment of the Limpopo River System in Mpumalanga Province in South Africa (Skelton 2001). The species thrives in impoundments in its native and introduced ranges (Mulder 1973). There may be other areas where this species has become established due to inter-basin transfer schemes from the Orange-Vaal River System.

Habitat View more ecological information

Population trend

Trend

The species seems to be abundant in slow-flowing reaches of rivers and thrives in dams such as the Vaal and Bloemhof dams on the Vaal River (Mulder 1973). There are many populations (native to six separate river systems). According to genetic variation between populations, only three main populations exist and can be classified as evolutionary significant units (ESUs) (Ramoejane 2016). These are the Orange, South Western (Gourits and Gamtoos) and South Eastern populations (Sundays, Bushmans, Great Fish, Keiskamma, Buffalo and Nahoon). Genetic divergence between the population from the southern-flowing systems in the Eastern and Western Cape and that from the Orange-Vaal System is extensive (Ramoejane 2016) and may require further taxonomic investigation. Within each major population grouping, there are several subpopulations (both lentic and lotic). There is no information about population trends for each of the populations or ESUs but if there is decline it is not suspected to be significant.

Threats

There are several threats to rivers where L. umbratus occurs but some of these may have resulted in benefits to this species, for example, construction of dams and weirs, increased eutrophication due to waste water treatment releases into rivers which increase levels of detritus, algae and zooplankton on which this species feeds. Hybridization between historically-isolated lineages of this species has already occurred in the Sundays River due to inter-basin transfer schemes between the Great Fish and Sundays Rivers (Ramoejane 2016). Heavy pollution due to industries and sewage overflow in the Gauteng Province has resulted in fish kills in the Vaal System and may have led to short term population fluctuations in sections of the Vaal River. Alien fishes (Micropterus salmoides) and habitat deterioration threaten the population in the Bushmans and Gourits River systems. The effect of African Sharptooth Catfish (Clarias gariepinus) invasions in the Gamtoos and Gourits systems is not well understood.

Uses and trade

The species is a detritivore and is thus rarely caught by anglers despite its good size. It however has been an important component of commercial net fisheries when these were operational in seven state dams in the Free State Province (Barkhuizen 2015). There are increasing reports of illegal netting (without permits) in rivers and dams of the Orange-Vaal System.

Conservation

There are a number of protected areas (e.g. National Parks, provincial nature reserves) that encompass parts of rivers and dams where L. umbratus occurs. Introductions associated with Orange-Fish (Orange and Great Fish rivers) and Cookhouse (Great Fish and Sundays Rivers) inter-basin water transfer schemes have resulted in hybridization between the previously-isolated Orange River and southern lineages of L. umbratus. Although hybridization between these lineages is not frequent or extensive, further translocations of individuals of genetically-differentiated (i.e. Orange-Vaal, South-western and South-eastern) populations among river systems and impoundments, such as Kat River (Great Fish River) and Slagboom (Sundays River), should be avoided (Ramoejane 2016).

References

[@article{18475,
 author = {Skelton, P.H.},
 title = {A Complete Guide to the Freshwater Fishes of Southern Africa},
 year = {2001}
}
,@electronic{2426,
 address = {www.iucnredlist.org},
 author = {IUCN},
 title = {The IUCN Red List of Threatened Species. Version 2017-3},
 year = {2017}
}
,@techreport{2428,
 address = {Trondheim},
 author = {Naesje, T.F., Hay, C.J., Nickanor, N., Koekemoer, J. , Strand, R and C.B. Thorstad},
 title = {Fish populations, gill net catches and gill net selectivity in the lower Orange River, Namibia, from 1995 to 2001},
 year = {2007}
}
,@phdthesis{63280,
 author = {Hamman, K.C.D},
 school = {Randse Afrikaanse Universiteit},
 title = {Aspekte van die visbevolkingsdinamika van die Hendrik Verwoerddam met verwysing na die ontwikkeling van ‘n visserybestuursplan. Ph.D. Proefskrif},
 year = {1981}
}
,@article{63280,
 author = {Tomasson, T., Bruton, M.N. and Hamman, K.C.D. },
 journal = {Fisheries Research},
 pages = {279--308},
 title = {The demography and management of large Cyprinids in a reservoir on the Orange River, South Africa},
 volume = {3},
 year = {1985}
}
,@phdthesis{63286,
 author = {Ramoejane, M. },
 school = {PhD thesis Rhodes University},
 title = {Genetic diversity, evolutionary relationships and conservation of southern African fishes in relation to water management},
 year = {2016}
}
,@phdthesis{63288,
 author = {Barkhuizen, L.M.},
 school = {University of the Free State},
 title = {An assessment of fish and fisheries in impoundments in the Upper Orange-Senqu and lower Vaal River Basin.},
 year = {2015}
}
,@article{63288,
 author = {Mulder, P.F.S.},
 journal = {Zoologica Africana},
 number = {1},
 pages = {15--24},
 title = {Aspects of the ecology of Labeo capensis and Labeo umbratus in the Vaal River.},
 volume = {8},
 year = {1973}
}
,]

How to cite this assessment

See the partners page

Send feedback about this assessment to SANBI

Red List of South African Species