Red List of South African Species

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Least Concern (LC)
Assessors: Dean Impson
Contributors: Ernst Swartz Roger Bills
Facilitators: Dewidine Van Der Colff
Reviewers: Domitilla Raimondo

Rationale (Changed due to Same category and criteria)

The species is widespread, in the Orange-Vaal River System of Southern Africa. It is however restricted to suitable habitat (rocky riffles, rapids and runs) within its overall range. There is little or no information available on small-scale distribution patterns, movement between possible suitable habitats or on population trends. However, its wide distribution suggests that criterion B is not applicable. There is no reliable information about population trends. Decline and possible extirpation from some tributaries of the Vaal River in the last 10 years may have occurred in Gauteng Province, but this is over a relatively restricted area compared to its overall range. Therefore, criterion A is not applicable. The species seems to occur in low numbers, but due to its wide range, overall population size is expected to be larger than 10,000 individuals. Therefore, criteria C and D are not applicable. No quantitative analysis has been done for this species. Therefore, criterion E is not applicable. 
There is concern, that the species is uncommon across its range, except in rivers that provide good habitat and water quality. Habitat alteration by weirs and dams and pollution (especially in tributaries of the Vaal River) have caused local declines and possibly even local extirpations. However, the wide distribution and therefore relatively large overall population size of this species precludes it from qualifying against any of the criteria thresholds, and it is therefore assessed as Least Concern (LC). This assessment was originally assessed in 2007 as Least Concern and was reviewed in 2016, new information since the 2007 assessment of this species has not resulted in a change in status and the species remains Least Concern.

Distribution

Widely distributed in rivers providing suitable habitat and water quality across the Orange-Vaal River System, the largest river system in South Africa, including the mainstem Orange and Vaal rivers (Skelton 2001, Skelton and Cambray 1981, Cambray 1984, Laurenson and Hocutt 1984). In the Orange it is found in the upper reaches in Lesotho (Senqu River) (Schrijvershof 2015) to the lower Orange at Grootpenseiland (Naesje et al. 2007), within the Richtersveld National Park. It has been translocated through inter-basin transfer schemes to the Great Fish River System and the Olifants catchment of the Limpopo River System (Laurenson and Hocutt 1984, Skelton 2001) and may also establish in other river systems that have been connected to the Orange-Vaal System.

Population trend

Trend

No estimate of population size is available, and the species can be uncommon or absent in detailed fish surveys (see Skelton and Cambray 1981), but also occasionally common in other surveys (e.g. upper Orange) at survey sites where there is good habitat (see Schrijvershof 2015). This species appears to be very habitat specific and favours rivers with rocky cobble beds that have riffles, rapids and runs (Naesje et al. 2007, Shrijvershof 2015), and good water quality. When appropriate gear (electrofishers) is used in preferred habitat, the species can be caught in reasonable numbers, and given its very wide distribution range, the total number of fishes in the Orange River alone is likely to be substantial (more than 10,000 individuals).

Threats

As this species prefers riffles and rapids with an abundance of rock cover and good water quality, sedimentation, particularly because of erosion in the upper Orange, Caledon and some Vaal catchments, is a major threat. A further threat is instream dams and weirs, which are common in the Orange River System. There are increasing levels of pollution in several rivers, especially those in the heavily industrialised Gauteng Province and A. sclateri is likely to have disappeared from several rivers (e.g. Klip River) where it was once common.

Uses and trade

This species is occasionally caught by anglers fishing faster flowing parts of rivers and using earthworm for bait. Being small and spiny (sharp pectoral and dorsal spines) the fish is usually returned to the water. We are not aware of this species being targeted by subsistence anglers.

Conservation

There are no conservation measures specifically for this species. The species however probably obtains some benefit from the Augrabies and Richtersveld National Parks which straddle sizable sections of excellent habitat in the middle and lower Orange River.

References 

[@article{18475,
 author = {Skelton, P.H.},
 title = {A Complete Guide to the Freshwater Fishes of Southern Africa},
 year = {2001}
}
,@article{2426,
 author = {Nelson, J.S.},
 title = {Fishes of the World. Fourth edition.},
 year = {2006}
}
,@book{2426,
 address = {Gland, Switzerland and Cambridge, UK},
 author = {Baillie, J. and Groombridge, B.},
 publisher = {International Union for Conservation of Nature},
 title = {1996 IUCN Red List of Threatened Animals},
 year = {1996}
}
,@article{2426,
 author = {IUCN},
 title = {IUCN Red List of Threatened Animals},
 year = {1990}
}
,@book{2426,
 address = {Gland, Switzerland and Cambridge, UK},
 author = {Groombridge, B.},
 publisher = {IUCN},
 title = {1994 IUCN Red List of Threatened Animals},
 year = {1994}
}
,@electronic{2426,
 address = {www.iucnredlist.org},
 author = {IUCN},
 title = {The IUCN Red List of Threatened Species. Version 2017-3},
 year = {2017}
}
,@article{2428,
 author = {Cambray, J.A.},
 title = {Fish populations in the middle and lower Orange River, with special reference to the effects of stream regulation},
 year = {1984}
}
,@article{2428,
 author = {Skelton, P.H. and Cambray, J.A.},
 title = {Freshwater fishes of the middle and lower Orange River},
 year = {1981}
}
,@article{2428,
 author = {Laurenson, L.J.B. and Hocutt, C.H.},
 title = {The introduction of the rock catfish, <i>Gephyroglanis sclateri/i<> into the Great Fish River via the Orange Fish Tunnel, South Africa},
 year = {1984}
}
,@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}
}
,@article{2428,
 author = {Niehaus, B.H., Steyn, G.J. & Rall, J.L},
 journal = {Water SA},
 number = {4},
 pages = {405--410},
 title = {Habitat preference and population structure of the rock catfish (Austroglanis sclateri) in the Senqunyane River, Lesotho},
 volume = {23},
 year = {1997}
}
,@phdthesis{2428,
 author = {Schrijvershof, J. },
 school = {North West University},
 title = {Biology and ecology of fishes of the Senqu River, Lesotho. MSc thesis},
 year = {2015}
}
,]
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