Red List of South African Species

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Endangered (EN)
B1ab(iii,v)+2ab(iii,v)
Assessors: Albert Chakona Martine Jordaan
Facilitators: Dewidine Van Der Colff
Reviewers: Jörg Freyhof

Rationale

Once widely distributed throughout the Heuningnes River System, remnant subpopulations are fragmented due to invasion by alien fish, mainly Bass species (Micropterus spp.). There are currently three known subpopulations which occur in three sub-catchments of the Heuningnes River System; the Kars, Grashoek and Nuwejaars (Chakona et al. 2013). However, the only viable subpopulation of this lineage occurs in the upper Kars River which is protected by a low water bridge that has prevented invasion of this section of the river by Micropterus spp. The effectiveness of this bridge as a long-term barrier is however uncertain. Only juveniles and sub-adults were recorded in the Grashoek and Nuwejaars sub-catchments during surveys conducted in 2008 and 2009. These two sub-catchments have been heavily invaded by Bass species (Micropterus spp.) which threaten the future survival of the Grashoek and Nuwejaars populations. Pseudobarbus sp. nov. ‘heuningnes’ has an extent of occurrence (EOO) of 209 km2 and an area of occupancy (AOO) of 20 km2, and is known from only three locations. It is experiencing continuous decline due to severe invasion in all of the sub-catchments where it currently occurs and a decrease in habitat quality. It therefore qualifies for the Endangered B1ab(iii,v)+2ab(iii,v). It should be noted that the Grashoek and Nuwejaars subpopulations are considered non-viable as their long-term survival is uncertain and highly unlikely. These subpopulations need to be closely monitored and the assessment needs to be adjusted accordingly. It must further 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

This lineage is endemic to the Heuningnes River System which drains the Agulhas Plain at the southern tip of Africa (Chakona et al. 2013).

Population trend

Trend

There are currently three known highly fragmented subpopulations which occur in the three sub-catchments of the Heuningnes River System; the Kars, Grashoek and Nuwejaars (Chakona et al. 2013). These three subpopulations are isolated from each other by the presence of alien piscivorous fishes.

Threats

Piscivorous invasive alien species are the single most important threat to this taxon. Bass species (Micropterus spp.) in particular have become established and thrive in the mainstem sections of the Kars, Grashoek and Nuwejaars (Chakona pers. obs.). Unlike the mountain streams where natural instream physical barriers such as waterfalls have curtailed the spread of invasive alien species elsewhere in the Cape Fold Ecoregion, coastal systems such as the Heuningnes lack such barriers. Alien species have therefore spread widely throughout the system, with the deep pool habitats, soft bottom substrate and gentle flow or static water offering ideal habitat for Micropterus spp. The low water bridge on the Kars River which has thus far prevented invasion of the upper Kars by Spotted Bass (Micropterus punctulatus) (two adult specimens of this species were caught immediately below the bridge during the 2008 survey). The effectiveness of the low water bridge as a long-term barrier is however uncertain.

Conservation

Currently there is no conservation plan in place to protect or assist the recovery of Pseudobarbus sp. nov. ‘heuningnes’. Immediate conservation measures are needed to secure the remaining stronghold of this lineage by erecting another more effective barrier below the low water bridge on the Kars River. There is also need for exploring the feasibility of eradicating aliens invasive fish in the river section below the low water bridge to facilitate recovery and spread of Pseudobarbus sp. nov. ‘heuningnes’ and other lineages of native species that are endemic to the Agulhas Plain (Galaxias sp. nov. 'heuningnes' and Sandelia sp. nov. 'Agulhas') (Chakona et al. 2013).

References 

[@article{18475,
 author = {Skelton, P.H.},
 title = {A Complete Guide to the Freshwater Fishes of Southern Africa},
 year = {2001}
}
,@article{126219629,
 author = {Barnard KH },
 journal = {Annals of the South African Museum},
 pages = {101--263},
 title = {Revision of the indigenous freshwater fishes of the S.W. Cape Region},
 volume = {36.0},
 year = {1943}
}
,@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}
}
,@electronic{2426,
 address = {www.iucnredlist.org},
 author = {IUCN},
 title = {The IUCN Red List of Threatened Species. Version 2017-3},
 year = {2017}
}
,@article{19890,
 author = {Chakona A, Swartz ER, Gouws G },
 journal = {PLoS ONE },
 number = {8},
 title = {Evolutionary drivers of diversification and distribution of a southern temperate stream fish assemblage: testing the role of historical isolation and spatial range expansion},
 volume = {8},
 year = {2013}
}
,@book{63387,
 address = {Gland, Switzerland and Grahamstown, South Africa},
 author = {Darwall, W. R. T.; Smith, K. G.; Tweddle, D. and Skelton, P.},
 publisher = {IUCN and SAIAB},
 title = {The status and distribution of freshwater biodiversity in Southern Africa},
 year = {2009}
}
,@article{57498415,
 author = {Chakona, A. and Swartz, E.R.},
 journal = {Zootaxa},
 number = {5},
 pages = {565--577},
 title = {A new redfin species, <i>Pseudobarbus skeltoni</i> (Cyprinidae, Teleostei), from the Cape Floristic Region, South Africa},
 volume = {3686},
 year = {2013}
}
,@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{107661025,
 author = {Swartz ER, Chakona A, Skelton PH, Bloomer P},
 journal = {Hydrobiologia},
 pages = {109--121},
 title = {The genetic legacy of lower sea-levels: does the confluence of rivers during the last glacial maximum explain the contemporary distribution of a primary freshwater fish (Pseudobarbus burchelli, Cyprinidae) across isolated river systems? },
 volume = {726},
 year = {2014}
}
,]
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