SANBI

Rationale

This is a range restricted species, known from two locations in The Olifants-Doring River System (ODRS), South Africa. Its extent of occurrence (EOO) is 41 km² (based on the total area within a minimum convex polygon around all known occurrences) and area of occupancy (AOO) is 20 km² (based on a 2x2 km² grid overlay on the range map). The population is severely fragmented (small and isolated subpopulations) and there is also a decline in mature individuals due to alien invasive fish, habitat degradation and water abstraction. The species does not occur in formal conservation areas. The species is listed as Critically Endangered B1ab(iii,v). It must be noted that the current method of determining AOO (2x2 km² grid overlay) significantly overestimates the AOO for this species and that the actual occupied habitat, when considering mean river width and river length, is only a small fraction of the reported AOO value of 20 km².

Distribution

The Doring Fiery Redfin Pseudobarbus sp. nov. 'doring' is a small cyprinid endemic to the Olifants-Doring River System (ODRS) of South Africa (Swartz 2005). It has only been recorded from the Driehoeks-Matjies and Breekkrans rivers of the Doring River System on the eastern side of the Cederberg Mountains where its range has contracted significantly as a result of the presence of alien invasive fish species (Swartz et al. 2004, Van der Walt 2014).

Habitat View more ecological information

Population trend

Trend

In the Driehoeks River, this species currently occurs in a few pools above a weir on Driehoek farm and in a small section of the Matjies River below Sanddrift campsite. Prior to the 1990s, records indicate a much wider range in the Driehoeks-Matjies River. The estimated subpopulation size for the Driehoeks River is estimated between 250 and 500 mature individuals. In the Breekkrans River its range has also shrunk compared to its historical distribution, and it is now present in a 2 km stretch above a natural Black Bass (Micropterus spp.) barrier. This seems to be a smaller subpopulation and a snorkel survey in 2013 recorded only 32 mature individuals (Van der Walt 2014). A fyke net survey of the same area in 2011 yielded 95 Doring Fiery Redfins, of which at least half were mature individuals, in three fyke net efforts (Jordaan and Marr unpublished data). Two subpopulations are thus known, the Driehoeks-Matjies River and the Breekkrans River.

Threats

Alien invasive fish species have significantly reduced the range of this lineage. There was probably a major, rapid reduction in range soon after the introduction of three Bass species (Micropterus spp.) into the Olifants-Doring River System (ODRS) in the 1930s and 1940s (de Moor and Bruton 1988). Pseudobarbus sp. nov. 'doring' mostly occupy the middle and lower reaches of tributary streams and the majority of these areas are invaded by Smallmouth Bass (Micropterus dolomieu), Spotted Bass (Micropterus punctulatus) and this would probably explain their current limited distribution (Van der Walt 2014). Largemouth Bass (Micropterus salmoides) was also introduced into the middle reaches of the Driehoek River and this remains a major threat to this subpopulation. Expansion of vineyards along the Driehoeks River also pose a threat due to a increased demand for irrigation water from this river, causing an increase in water abstraction.

Uses and trade

Pseudobarbus phlegethon sensu lato is listed as an Endangered Wild Animal under Schedule 1 of the Provincial Nature Conservation Ordinance for the Western Cape, thereby preventing the collection and trade of the species without a permit. It is sometimes kept in public aquaria for awareness purposes. Pseudobarbus sp. nov. 'doring' will be included on the listed species in the near future.

Conservation

CapeNature is in the process of rehabilitating the Breekkrans River by eradicating invasive alien trees from the riparian zone and plans to eradicate invasive alien fish (Bass species (Micropterus spp.) and Bluegill Sunfish (Lepomis macrochirus)) from 6 km of river. The first step is to construct an alien fish barrier 6 km below the upper limit of alien invasive Bass species in the river. An environmental impact study for the proposed structure has been completed with a positive decision from the provincial authority. The construction of this barrier is planned for 2017 with a rotenone treatment planned the following year. CapeNature is considering introducing this taxon, as a conservation translocation, to the middle reaches of the Krom River (a tributary of the Matjies River) once alien invasive fishes have been eradicated (planned 2017/18). CapeNature has recently published a report on the priority rivers for fish conservation in the ODRS for awareness and management purposes (Impson et al. 2016), and both the Breekkrans and Driehoek-Matjies rivers are included.

References

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,]

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