Barbus calidus, the Clanwilliam redfin, is a ray-finned fish species in the family Cyprinidae. It is placed in the "wastebin genus" Barbus – the typical barbels and relatives – by default. But actually it is far less closely related to the typical barbels than to the South African redfins in Pseudobarbus, and may well belong in the latter genus. Like Pseudobarbus but unlike most other African "barbs", it is tetraploid. Its closest living relative is probably the Twee River redfin (B. erubescens).
Distribution and ecology
It is endemic to the Western Cape Province of South Africa, where it occurs in the upper Olifants River and its tributaries – the Biedou, Boontjies, Boskloof, Breekkrans, Driehoeks, Dwars, Eselbank, Jan Dissels, Matijes, Noordhoeks, Oudste, Ratels, Rondegat, Thee and Tra Tra Rivers – near Clanwilliam and Keerom.
It inhabits the pools and shallower water in larger clear and slightly acidic mountain streams. They are insectivores, eating mainly small mayflies (Baetidae), non-biting midges (Chironomidae) and ants (Formicidae). The breeding season is lengthy and lasts most of the summer, from November to January. Schools of adults form to migrate to shallow pools with slow-moving water and spawn between rocks and boulders, depositing the eggs in crevices between these.
Status and conservation
This species is considered Vulnerable by the IUCN, mainly due to the adverse impact of the introduced smallmouth bass (Micropterus dolomieu) on its population. The most drastic declines have been in the past, and though the species is still declining it is not doing so at an alarming rate; wherever the perch has not become established yet it is actually rather plentiful. Bluegills (Lepomis macrochirus) and rainbow trouts (Oncorhynchus mykiss) are other introduced species that are significant as predators of younger Clanwilliam redfins. Banded Tilapia (Tilapia sparrmanii) is yet another introduced fish that has an adverse effect on the stocks of B. calidus, in its case due to competition for food. The other main threat is water pollution and other forms of unsustainable water use. Particularly the conversion of riparian lands for citrus plantations, with the resultant uninhibited runoff of pesticides and fertilizers, is considered very harmful.
The Clanwilliam redfin occurs in the Cederberg Wilderness Area and the Matjies River Nature Reserve, where it is at least safe from habitat destruction. It is listed as Endangered by the Nature Conservation Ordinance of Western Cape Province. For the time being, it may not be killed or caught. The species is on display in public aquaria of Cape Town, Clanwilliam and Jonkershoek to educate the public on its conservation needs.
- de Graaf et al. (2007)
- Impson & Swartz (2007)
- de Graaf, Martin; Megens, Hendrik-Jan; Samallo, Johannis & Sibbing, Ferdinand A. (2007): Evolutionary origin of Lake Tana's (Ethiopia) small Barbus species: indications of rapid ecological divergence and speciation. Anim. Biol. 57(1): 39-48. doi:10.1163/157075607780002069 (HTML abstract)
- Impson, D. & Swartz, E. (2007). "Barbus calidus". IUCN Red List of Threatened Species. Version 2008. International Union for Conservation of Nature. Retrieved 20 September 2009.