Treur River barb  (Barbus treurensis)

The Treur River barb is cllassified as Endangered (EN) on the IUCN Red List (1).

The Treur River barb (Barbus treurensis) is a little-known freshwater fish with a spindle-shaped body. It is dusky in appearance with a translucent olive-brown colour on the top and silvery white on the underside (3). The narrow part of the Treur River barb’s body, where the body joins the tail (4), is marked with a dark band, and the sides are patterned with an irregular arrangement of spots along the side of the fish (5). It has two well developed barbs as well as comparatively large and heavily pigmented scales (3).

The Treur River barb occurs at only two sites in Mpumalanga, a province of South Africa. It has only recently been successfully reintroduced to the Treur River, were it was once a native species (1). The Treur River barb also occurs in the Blyde River, with the only remaining population situated above a waterfall in the upper reaches of the river (1).

The Treur River barb lives in moderately deep rocky pools and clear, cool streams (4). It shows a preference for main channel areas (1). It is generally found at elevations of 1,370 to 1,520 metres above sea level, at temperatures below 20 degrees Celsius (3).

This species primarily feeds on invertebrates (predominantly insects) but can also feed on filamentous algae (3).The Treur River barb has several naturally occurring predators including the claw toed frog, (Xeopus leavis), the malachite kingfisher, (Alcedo cristata) and the spot-necked otter (Lutra maculicollis) (3).

The Treur River barb has a particularly short breeding season, which begins at the start of the rainy season in October or November. The female Treur River barb is able to produce up to two thousand eggs during this period (2). Both the male and female develop round nodules called tubercles on their heads, indicating that they have reached sexual maturity (4). Spawning takes place in riffles, and the resulting juveniles shelter in the backwater areas of the river (3).

The Treur River barb can live for up to seven years (3).

The main reason for the decline of the Treur River barb population is believed to have been the introduction of predatory alien fish stock species (3). In particular, introduced predators such as the rainbow trout (Oncorhynchus mykiss) and small mouth bass (Microterus dolomieu) have had a major impact on this species when they were introduced to the Treur River (1) (3).

In 1970, the only area in which the Treur River barb occured, Bendigospruit, was declared an International Biological Program (IBP) conservation site. This status restricted practices such as the introduction of new fish or bird species to the area, and this has reduced disturbances to the stream and therefore to the Treur River barb (5). The land owners of the site also have their own conservation plan which includes clearing invasive plant species near the river bank (3).

Prior to 1996, the population of the Treur river barb was considered by scientists to be in decline. However, due to these conservation measures the Treur River barb population is now stable (1). In addition to this both sites at which the Treur River barb occurs (upper reaches of the Blyde River and the Treur River) have been made national heritage sites in order to continue the protection of this species (1).

Regardless of these measures, alien predatory species may potentially be introduced in the future (1). Monitoring of the Treur River barb’s habitat and population is therefore essential to avoid a further population decline. Additional research into identifying suitable alternative sites which the Treur River barb could be introduced to if its natural habitat were to become unsuitable is also advisable (3). 

Find out more about the Treur River barb:

• FishBase - Treur River barb:
  http://www.fishbase.org/summary/Barbus-treurensis.html