Riversong's very own rare and endangered fish

Riversong's river, the Twee River, forms part of the greater Olifants-Doring River System, which according to a brochure on the Cederberg by CapeNature has the highest number of endemic fish species of any river system in South Africa. Of the ten recorded species, eight are endemic to the area and nine are threatened according to IUCN criteria*. The fish that interests me is the Twee River Redfin which is listed as Critically Rare on the IUCN Red List. The Twee River Redfin is a medium-sized minnow that reaches an adult size of about 120 mm. The large eyes are on either side of the head and there are two pairs of barbels near the mouth. The top part of the body is olive brown with a dark band running the length of the body while the ventral side is silvery white. Breeding adults of both sexes develop small tubercles on top of the head and body. The base of the fins at this time are red and breeding males turn a deep bronze-red colour.
HABITAT
Adults prefer deep rocky pools that are surrounded by aquatic vegetation such as palmiet. Juvenile redfins are often found in backwater areas beneath clumps of palmiet.
LIFE HISTORY
This species feeds on aquatic invertebrates in mid-water or at the bottom of the pools. It breeds in late spring and summer when schools of males gather near rocky crevices and individual females join these spawning groups. Juvenile Twee River Redfins are often seen with schools of Cape Galaxias, Galaxias zebratus.
DISTRIBUTION
Endemic to the eastern Cederberg part of the Olifants River System in the Western Cape. They are only found in the Twee River catchment which includes the Middeldeur and Suurvlei Rivers.

Click here for a brochure containing more information about the Twee River Redfin.

*Seven endemic fish species known to occur in the Cederberg Nature Reserve Complex include three large cyprinids, namely the Clanwilliam Yellowfish (Labeobarbus capensis), the Clanwilliam Sawfin (Barbus serra) and the Clanwilliam Sandfish (Labeo seeberi); three smaller cyprinids, namely the Clanwilliam Redfin (Barbus calidus), the Fiery Redfin (Pseudobarbus phlegethon) and the Twee River Redfin (Barbus erubescens) and the Clanwilliam Rock Catfish (Austroglanis gilli). A second species of rock catfish, the much rarer and Endangered Austroglanis barnardi also occurs in the Olifants River system but is not known to occur within the boundaries of the reserve complex. In addition to these species, the Cape Galaxias (Galaxias zebratus) also occurs in some rivers in the reserve complex, but this species is not endemic to the Olifants-Doring River System. The Cape Kurper (Sandelia capensis) which is indigenous to a number of other river systems in the Cape Floristic Region, is present as an alien invasive species in the Twee River catchment.
Photo: CapeNature.