Red List of South African Species

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Endangered (EN)
B1ab(ii,iii)+2ab(ii,iii)
Assessors: Martine Jordaan Albert Chakona
Contributors: Ernst Swartz Dean Impson
Facilitators: Dewidine Van Der Colff
Reviewers: Domitilla Raimondo

Rationale (Changed due to Same category but change in criteria)

The Keurbooms Redfin (Pseudobarbus sp. nov. ‘Keurbooms’) is restricted to the Keurbooms and Bitou River Systems on the South Coast of the Cape Fold Ecoregion, South Africa. Little is known about its biology and ecology but it is known to inhabit headwater habitat. The two river systems represent separate populations and locations as a common estuary separates them and present a barrier to redfin migration between the two systems. A single known population exists in the Kransbos tributary in the Bitou River. Known distributions in the Keurbooms system may indicate the presence of three separate populations, two in the Palmiet tributary (Langbos and Diep Rivers) and another in the upper Keurbooms. The degree to which these populations may be separated by the presence of alien invasive fishes and non-suitable habitat is not clear and requires further investigation. The Keurbooms Redfin is threatened by the presence of non-native piscivorous fishes including Rainbow Trout (Oncorhynchus mykiss), Brown Trout (Salmo trutta) and Black Bass species (Micropterus species). Additional threats include commercial forestry activities that largely impact instream habitat through increased sedimentation. The Palmiet tributary population exists within the Tsitsikammma section of the Garden Route National Park where it is safeguarded against land use impacts, but the extent to which this population is secured from potential invasion by alien fishes from the mainstem river section is unknown. The upper Keurboooms population exists outside of any protected area and is therefore vulnerable to the impacts of both invasive fishes and poor land use practices, including unsustainable levels of water abstraction. These threats will likely be exacerbated by future climate change impacts. The Kransbos tributary population in the Bitou River System currently occurs outside of any formally protected area. This species has an extent of occurrence (EOO) of 262 km2 and an area of occupancy (AOO) of 40 km2 (calculated using 2x2 km2 grid). Presently there are four subpopulations and two locations which are defined based on the distribution of invasive alien species. This may change if better information on the presence and location of instream invasion barriers become available. The Keurbooms Redfin thus meet the qualifying thresholds for being listed as Endangered B1ab(ii,iii) + B2ab(ii,iii).

Distribution

The Keurbooms Redfin  is restricted to the Keurbooms and Bitou River systems (Swartz et al. 2009).

Population trend

Trend

Recent surveys in the Kransbos tributary of the Bitou River System reported the presence of an intact Keurbooms Redfin population (Diedericks and Roux 2014). These authors reported electrofishing catch rates of 20-70 individuals at a number of sites with all size classes present and catch per unit effort (CPUE) values ranging from 203-210 fish/minute of electrofishing. Additional sampling on the Rondebos tributary of the Bietou River yielded no fish records and the presence of the Keurbooms Redfin in this tributary should be investigated with further surveys, especially given that this tributary is located within the Harkerville section of the Garden Route National Park. Within the Keurbooms System a survey by Russell (2002) reported the presence of a number of native fish species, including Keurbooms Redfin in the Palmiet tributary of the Keurbooms River. Here CPUE values of 0.3-1.2 fish/minute of electrofishing were reported but no indication was given with regard to size class distribution. The status of the population in the upper Keurbooms River is unknown and should be verified through surveys.

Threats

The Keurbooms Redfin, as with the majority of other native redfins of the region are vulnerable to impacts from invasive alien fish species. Historical records exist for the presence of two species of Black Bass (Micropterus salmoides, and M. punctulatus) in the Keurbooms River System and Smallmouth Bass (M. dolomieu) in the Bietou River System (CapeNature State of Biodiversity Database). In addition, Rainbow Trout (Oncorhynchus mykiss) and Brown Trout (Salmo trutta) is present in the upper Keurbooms River where an existing trout farm is managing the riverine trout population for sustainability. De Moor & Bruton (1988) described S. trutta as “thriving” in the Keurbooms River despite the supposed intolerance of this species of low pH, peat-stained rivers characteristic of the southern Cape coastline. Skelton (1994) recorded Rainbow Trout in the mainstream of the upper reaches of the Keurbooms River while the surveys of Russell (2002) did not detect this or any other invasive species in the Palmiet River section of the Keurbooms River System. Similarly, Diedericks and Roux (2014) did not report the presence of any invasive species in the Kransbos tributary of the Bietou. The current extent of alien fish invasions in both systems are unknown and should be determined through focused field surveys as the presence of these species represent the major threats to the long-term persistence of redfin populations in these river systems.

Habitat related threats appear to be emanating from the commercial forestry activities in both the Bietou and Keurbooms systems as reported by Diedericks and Roux (2014). These impacts include reduced surface runoff, increased sedimentation and increased shading of habitat by canopy cover. Habitat impacts related to large scale water abstraction and subsequent reduced flows are also a key threat but the degree of these impacts require further investigation.

Uses and trade

All indigenous fish species of the Western Cape Province are listed as Endangered Wild Animals 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. Translocations of indigenous freshwater fish species are controlled by Cape Nature’s Indigenous Fish Utilisation policy (Jordaan et al. 2016).

Conservation

No specific conservation actions are proposed for this species at present but an in depth survey to determine native and non-native fish distributions and invasion barriers are a high priority.

References 

[@techreport{2426,
 address = {Stellenbosch},
 author = {Jordaan, M., Impson, D. and de Villiers, P},
 institution = {Cape Nature},
 title = {CapeNature policy on the transport and utilisation of indigenous freshwater fishes of the Western Cape Province},
 year = {2016}
}
,@techreport{2562,
 address = {Pretoria, South Africa},
 author = {De Moor, I.J. and Bruton, M.N.},
 institution = {Foundation for Research Development, Council for Sscientific and Industrial Research},
 title = {Atlas of alien and translocated indigenous aquatic animals in southern Africa},
 year = {1988}
}
,@article{18477,
 author = {Swartz, E.R.},
 title = {Phylogeography, phylogenetics and evolution of the redfins (Teleostei, Cyprinidae, <i>Pseudobarbus</i>) in southern Africa.},
 year = {2005}
}
,@inbook{63398,
 author = {},
 booktitle = {Diversity and distribution of freshwater fishes in East and Southern Africa},
 editor = {Skelton, P.H.},
 pages = {95--131},
 publisher = {Annales Musee Royal de 1'Afrique Centrale, Tervuren, Belgique, Sciences Zoologiques},
 title = {Biological diversity of African fresh- and brackish water fishes},
 year = {1994}
}
,@techreport{63398,
 address = {Cape Town},
 author = {Diedericks G & Roux F },
 title = {A survey of Cyprinidae: Pseudobarbus species in rivers and streams on Buffelsnek Plantation.},
 year = {2014}
}
,@article{63398,
 author = {Russell I.A.},
 journal = {Koedoe},
 number = {2.0},
 pages = {13--17},
 title = {Freshwater fishes of Tsitsikamma National Park},
 volume = {45.0},
 year = {2002}
}
,@article{63398,
 author = {Swartz ER, Skelton PH, Bloomer P. },
 journal = {Molecular Phylogenetics and Evolution},
 pages = {75--84},
 title = {Molecular phylogenetics and evolution phylogeny and biogeography of the genus Pseudobarbus (Cyprinidae): Shedding light on the drainage history of rivers associated with the Cape Floristic Region},
 volume = {51.0},
 year = {2008}
}
,]
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