Berg River Redfin

Tuesday, November 26, 2013 by CapeNature

Berg river redfin

COMMON NAME
Berg River redfin
Bergrivier-rooivlerkie

SCIENTIFIC NAME
Pseudobarbus burgi

CONSERVATION STATUS
Endangered

IDENTIFICATION
A true redfin grows to about 120 mm with a fusiform body, meaning tapering at both ends. Two pairs of barbels are present near the mouth with the anterior pair being much shorter and only visible in adult specimens. These fish are brown on top and silvery white below. The adults of both sexes have bright red fins, especially in the breeding season. An irregular dark band along the body is more prominent in the juveniles than in the adults. Sexually mature males develop large conical tubercles on their heads during the breeding season.

HABITAT
Nowadays they are found in small, clear, flowing mountain tributaries of the Berg River that have good flow and very good water quality. Adults prefer deeper pools with good cover in the form of rocks, Pal- miet and overhanging vegetation.

LIFE HISTORY
They are bottom to midwater feeders and prey on aquatic invertebrates such as corixid bugs and chironomid larvae, as well as zoo- plankton and algae. The Berg River redfin is capable of jumping when ascending rapids. They breed in summer and like most redfins probably spawn near crevices between rocks.

DISTRIBUTION
This once widespread species has been extirpated from much of its former range due to habitat degradation and the predatory impacts of alien fish species such as bass and trout. They used to occur in the Berg mainstem probably down to Paarl and were widespread in the Klein Berg, Wemmers, Dwars and Vier-en-Twintig rivers. They are now restricted to several mountain streams where habitat is good and bass are absent. Berg River redfins used to occur in the Eerste River but are now extinct here due to predation by trout.

THREATS

  • Introduced alien predators such as basses (Micropterus spp.), blue-gill sunfish (Lepomis macrochirus) and rainbow trout (Onchorynchus mykiss) are largely responsible for the elimination of this species from much of its natural range.
  • Pollution (both agricultural and industrial) affects large sections of their habitat.
  • Excessive water abstraction, especially during the dry season, is a severe threat to small streams.
  • Channelisation of streambeds and resultant loss of suitable habitat.
  • Invasive alien plant species (e.g. black wattle) damage river banks and use large amounts of water.

CONSERVATION

  • Development and implementation of a Biodiversity Management Plan
  • Species monitoring of all good populations of the species every 3 years by CapeNature and partner agencies.
  • Key populations have been determined and are listed as Critical Biodiversity Areas for fish conservation. Several areas have been identified at national level as Freshwater Ecosystem Protected Areas.
  • More detailed research into the biology and ecology of the species should be conducted to optimise conservation efforts.
  • Eradication of alien fish species from priority river rehabilitation areas that include removing alien vegetation from riparian zones in priority fish conservation catchments.

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