Redtailed black shark (Epalzeorhynchos bicolor)

Redtailed black shark
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Redtailed black shark fact file

Redtailed black shark description

GenusEpalzeorhynchos (1)

An eye-catching fish that was previously believed to be extinct in the wild (1), the redtailed black shark (Epalzeorhynchos bicolor) has a misleading name as it is not actually a shark, but is related to carp. It does, however, have a striking, bright red tail fin as its name suggests (2).

The rest of the body of this small fish is black or purplish-black. The redtailed black shark has a small, downturned mouth, and two fleshy projections (barbels) extend from the edges of the mouth (2) (3). The female redtailed black shark is less brightly coloured than the male (4).

Also known as
red tailed shark, redtail shark, redtail sharkminnow, red-tailed labeo.
Length: up to 10 cm (2)

Redtailed black shark biology

As it was until recently thought to be extinct in the wild, there is little information available on the redtailed black shark’s biology and behaviour in its natural habitat. The scant information on this fish probably comes from observations of it in captivity.

An omnivorous fish, the redtailed black shark feeds on plant matter and small animals that live on the river bed (2). It spawns in rocky caves, and the young hatch after just 30 to 60 hours. Four days after hatching, the young are free-swimming, but do not develop the characteristic red tail until seven to ten weeks old (3). The redtailed black shark lives for five to eight years (3).


Redtailed black shark range

The redtailed black shark is endemic to Thailand, where it previously inhabited the Mae Khlong, Chao Phraya and Bang Pakong River Basins. It is now known only from a single location in the Chao Phraya basin (1).


Redtailed black shark habitat

The redtailed black shark is a tropical freshwater fish species (1). In the wild, it has been recorded in clear and muddy waters in rivers and floodplains (2) (3), and in lowland streams with rocky or sand gravel bottoms (1).


Redtailed black shark status

The redtailed black shark is classified as Critically Endangered (CR) on the IUCN Red List (1).

IUCN Red List species status – Critically Endangered


Redtailed black shark threats

The distinctive redtailed black shark was previously believed to be extinct in the wild, and was known only from captivity. The aquarium fish trade may be one of the reasons for its decline in the wild, although there is not yet any evidence to support this theory. A more likely reason for the redtailed black shark’s demise is habitat alteration; during the 1970s, numerous dams were constructed in Thailand, which probably had severe impacts on the rivers in the region. Large areas of swamps in Thailand have also been drained, destroying potential habitat for the redtailed black shark (1).

More recently, the redtailed black shark has been rediscovered in Chao Phraya, but it is only known from a single, tiny area. The major threat to the wild population is currently pollution from agricultural and domestic sources. Road building and the development of dams are also affecting its habitat and altering water flow, while agricultural activities may be causing siltation of rivers (1).


Redtailed black shark conservation

Due to its popularity in the aquarium trade (tens of thousands of captive bred individuals are exported annually from Thailand) (1), the redtailed black shark’s survival is probably not currently at risk.

However, urgent conservation measures may be needed to preserve the remaining wild population of this striking fish. More information is needed on the redtailed black shark’s presence in the wild, and a reintroduction programme and species recovery action plan have been recommended. As commercially bred captive stock may not be genetically suitable for reintroduction into the wild, a captive breeding programme has also been recommended, focusing specifically on this species’ conservation (1).

View information on this species at the UNEP World Conservation Monitoring Centre.

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This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:

This species information was authored as part of the Arkive and Universities Scheme.


Fleshy projections near the mouth of some aquatic vertebrates.
A species or taxonomic group that is only found in one particular country or geographic area.
Feeding on both plants and animals.
Produces and deposits large quantities of eggs in water.


  1. IUCN Red List (June, 2011)
  2. Vidthayanon, C. (2005) Thailand Red Data: Fishes. Office of Natural Resources and Environmental Policy and Planning, Bangkok, Thailand.
  3. Peoria Zoo Species Fact Sheet - Red-tailed Shark (December, 2010)
  4. Riehl, R. (Ed.) (1997) Aquarium Atlas 1. Hans A. Baensch, Melle, Germany.

Image credit

Redtailed black shark  
Redtailed black shark

© Neil Hepworth

Neil Hepworth


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