Red List of South African Species

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Endangered (EN)
B1ab(ii,iii,v)+2ab(ii,iii,v)
Assessors: Albert Chakona Olaf Weyl Bruce Ellender
Contributors: Ernst Swartz Dean Impson
Facilitators: Dewidine Van Der Colff
Reviewers: Domitilla Raimondo Edward Harrison

Rationale

Once common and widely distributed throughout the Baakens, Swartkops and Sundays rivers systems, the species suffered severe decline in distribution and abundance, mainly due to invasion by alien predators and competitors (Ellender et al. 2011, Kadye and Booth 2012), as well as deterioration of water quality and loss of critical habitat. Currently invasion by non-native fishes is considered the primary threat to the species' future survival (Swartz and Impson 2007, Kadye and Booth 2012, Ellender 2013). Despite two of the three subpopulations being situated in formal protected areas (Addo Elephant National Park and Groendal Wilderness Area), there is no protection from non-native fishes which are present in the mainstream sections of the rivers (Ellender et al. 2011, 2015). There has been significant research on the distribution of this species since the last assessment. It was found that subpopulations within rivers were fragmented and now limited to headwater streams above barriers to invasive Largemouth Bass (Micropterus salmoides) (Ellender et al. 2011, Ellender 2013). The alien African Sharptooth Catfish (Clarias gariepinus) is an emerging invader that has recently penetrated into the upper reaches of some headwater tributaries of the Sundays and Swartkops rivers beyond the upper limits of Largemouth Bass (Ellender et al. 2011). While the impacts of these invasions are yet to be assessed, they pose a significant threat to the remnant subpopulations of native species, which now only persist in these headwater tributaries. Studies have provided evidence that the available habitat for Pseudobarbus afer sensu stricto is decreasing due to invasion by alien fishes (Weyl et al. 2010; Ellender et al. 2011, 2015; Ellender 2013). When this is viewed with the concomitant impact of the 2008 and 2009 droughts, the impact of alien fishes is likely to be exacerbated (Weyl et al. 2010). Ellender (2013) estimated that subpopulations of this species have been excluded from ca 20% of habitat in the Swartkops River System, while only two individuals were captured from a single locality during a recent comprehensive survey of the Baakens River System (Muller et al. 2015). The species has an extent of occurrence (EOO) of 2,183 km2 and an area of occupancy (AOO) of 56 km2 (calculated using a 2x2 km2 grid) and is known from three locations (the Baakens (whose long-term survival is in doubt), the Swartkops, and Sundays (there are no barriers to protect the remnant populations from invasion)) and there is decline in number of mature individuals due to predatory impacts of invasive alien species. Given that the Baakens River is a heavily modified urban river that is heavily invaded by alien fishes and impacted by pollution this subpopulation is considered at high risk of extinction (Muller et al. 2015). Pseudobarbus afer sensu stricto is assessed as Endangered category under criteria B1ab(ii,iii,v)+2ab(ii,iii,v).

Distribution

The species is restricted to three river systems (Baakens, Swartkops and Sundays) in the eastern Cape Fold Ecoregion, and it is endemic to Eastern Cape Province, South Africa (Chakona and Skelton 2017; Swartz et al. 2007, 2009). Long-term survival of the Baakens subpopulation is uncertain (see Threats).

Population trend

Trend

At least three subpopulations survive in the Sundays River System in tributaries draining the Suurberg Mountains and there are at least five healthy subpopulations in the Swartkops River System. However, these subpopulations constitute less than five locations as they are not protected from invasion by non-native fishes which are common in the mainstreams. In the mainstream of the Sundays and Swartkops River this fish is absent, presumably extirpated by invasive bass (Micropterus spp.), and headwater stream populations have been shown to have been excluded from ca 20% of habitat in the Swartkops River System (Ellender 2013). In a recent survey in the Baakens River only two individuals were sampled from a single site (Muller et al. 2015). Given that the Baakens River is a heavily modified urban river with significant threats to the population (see Threats), the Baakens River population can therefore be considered to be in severe decline.

Threats

Alien invasive fish species, especially bass (Micropterus spp.) have severely reduced the historical range of this species (Skelton 1993) and isolated subpopulations to headwater stream reaches above physical barriers that limit the distribution of alien predators (Ellender 2013). The impact of other alien fish species, such as African Sharptooth Catfish (Clarias gariepinus), on this species is not well documented or understood but this predatory species has now penetrated well above the limits of the bass invasion in the Sundays and Swartkops River systems (Ellender et al. 2015). The Baakens River is a heavily modified urban river that is also heavily invaded by alien fishes and impacted by pollution. These impacts are further exacerbated by the synergistic impacts of the droughts of 2008/9, which decreased wet stream length in the Sundays tributaries reducing it to a few isolated pools and thus concentrating the impact of invasive species (Weyl et al. 2010). Long-term survival of the Baakens subpopulation is therefore uncertain (Muller et al. 2015).

Conservation

Some subpopulations fall within formally protected areas such as Addo Elephant National Park and the Groendal Nature Reserve; however, the protection afforded by these areas is ineffective against invasion from alien fish species. While some populations appear to be well protected, others are vulnerable to invasion (Ellender 2013).

References 

[@article{18475,
 author = {Skelton, P.H.},
 title = {A Complete Guide to the Freshwater Fishes of Southern Africa},
 year = {2001}
}
,@article{182803,
 author = {Muller, C., Strydom, N.A. and Weyl, O.L.F},
 journal = {Water South Africa},
 number = {5},
 pages = {746--752},
 title = {Fish community of small, temperate, urban river in South Africa},
 volume = {41.0},
 year = {2015}
}
,@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}
}
,@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}
}
,@book{2427,
 address = {Gland, Switzerland and Cambridge, UK},
 author = {IUCN Conservation Monitoring Centre},
 publisher = {IUCN},
 title = {1986 IUCN Red List of Threatened Animals},
 year = {1986}
}
,@article{2564,
 author = {Skelton, P.H.},
 title = {A taxonomic revision of the redfin minnows (Pisces, Cyprinidae) from southern Africa},
 year = {1988}
}
,@phdthesis{2573,
 author = {Ellender BR },
 school = {Rhodes University},
 title = {Ecological consequences of non-native fish invasions in Eastern Cape headwater streams},
 year = {2013}
}
,@article{2573,
 author = {Cambray JA },
 journal = {Environmental Biology of Fishes},
 pages = {247--268},
 title = {The comparative reproductive styles of two closely related African minnows (Pseudobarbus afer and P. asper) inhabiting two different sections of the Gamtoos River system},
 volume = {41},
 year = {1994}
}
,@article{18477,
 author = {Swartz, E.R.},
 title = {Phylogeography, phylogenetics and evolution of the redfins (Teleostei, Cyprinidae, <i>Pseudobarbus</i>) in southern Africa.},
 year = {2005}
}
,@article{19890,
 author = {Ellender BR, Weyl OLF and Swartz E },
 journal = {African Zoology },
 pages = {39--46},
 title = {Invasion of a headwater stream by non-native fishes in the Swartkops River system, South Africa},
 volume = {46},
 year = {2011}
}
,@article{57498415,
 author = {Skelton, P.H.},
 title = {On bass in Blindekloof - the impact of an alien predator on a wilderness stream},
 year = {1993}
}
,@article{57498415,
 author = {Swartz ER, Skelton PH and Bloomer P },
 journal = {Molecular Phylogenetics and Evolution },
 pages = {75--84},
 title = {Phylogeny and biogeography of the genus Pseudobarbus (Cyprinidae): Shedding light on the drainage history of rivers associated with the Cape Floristic Region},
 volume = {51},
 year = {2009}
}
,@article{57498415,
 author = {Swartz ER, Skelton PH, Bloomer P },
 journal = {Journal of Biogeography },
 number = {12},
 pages = {2086--2099},
 title = {Sea-level changes, river capture and the evolution of populations of the Eastern Cape and fiery redfins (Pseudobarbus afer and Pseudobarbus phlegethon , Cyprinidae) across multiple river systems in South Africa},
 volume = {34},
 year = {2007}
}
,@article{107649522,
 author = {Swartz, E.R., Flemming, A.F. and Mouton, P. le F.N.},
 title = {Contrasting genetic patterns and population histories in three threatened redfin species (Cyprinidae) from the Olifants River System, western South Africa},
 year = {2004}
}
,@article{107654052,
 author = {Ellender BR, Woodford DJ and Weyl OLF},
 journal = {Biological Invasions  },
 pages = {57--61},
 title = {The invasibility of small headwater streams by an emerging invader, Clarias gariepinus.},
 volume = {17},
 year = {2015}
}
,@article{107654052,
 author = {Chakona A and Skelton PH },
 journal = {ZooKeys},
 pages = {109--140},
 title = {A review of the Pseudobarbus afer (Peters, 1864) species complex (Teleostei, Cyprinidae) in the eastern Cape Fold Ecoregion of South Africa},
 volume = {657},
 year = {2017}
}
,@article{107654052,
 author = {Ellender BR and Weyl OLF},
 journal = {Koedoe},
 number = {1},
 pages = {Art. #1258, 8 pages},
 title = {Resilience to an unpredictable high-magnitude flood by imperilled headwater stream fish},
 volume = {57},
 year = {2015}
}
,@article{107654052,
 author = {Kadye WT and Booth AJ },
 journal = {Journal of Applied Ichthyology },
 number = {791-799},
 title = {Inter-seasonal persistence and size-structuring of two minnow species within headwater streams in the Eastern Cape, South Africa. },
 volume = {28},
 year = {2012}
}
,@electronic{107654052,
 address = {www.iucnredlist.org},
 author = {Swartz, E. & Impson, D},
 title = {<i>Pseudobarbus afer</i>},
 year = {2007}
}
,@article{107654052,
 author = {Weyl, P.S.R., De Moor, F.C., Hill, M.P. and Weyl, O.L.F.},
 journal = {African Journal of Aquatic Science},
 pages = {273--282},
 title = {The effect of largemouth bass Micropterus salmoides on aquatic macroinvertebrate communities in the Wit River, Eastern Cape, South Africa},
 volume = {35},
 year = {2010}
}
,]
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