Order : Cypriniformes
Family : CYPRINIDAE
Species : Mystacoleucus marginatus
Total Length (includes tail fin) : 20 cm
(Fishbase, 2026)

Mystacoleucus marginatus (Torrent Barb) is a widespread cyprinid that inhabits fast-flowing, clear streams and small rivers in many parts of Southeast Asia. It can tolerate various substrates including sand, gravel and rocky habitats, and streams which contain driftwood and tree branches (Ahmad, 2020).

According to Fishbase (2026), it is one of 8 in the genus; synonyms include Barbus marginatus and Barbus obtusirostris.

The examples shown here were identified as Mystacoleucus marginatus based on their body and fin shape, the curved dark markings at the base of each scale on the flanks, and the black margins of the dorsal fin.

The scales are silvery and thus highly reflective. In Figures 1 and 3 the colour of the surroundings and prevailing ambient light gives the appearance that these two examples are different colours; Figure 1 was photographed beneath a green forest canopy, whilst Figure 3 was photographed under direct sunlight.

Mystacoleucus marginatus occurs in Myanmar, southern China (Yunnan province), Thailand, Cambodia, Laos, Vietnam, Peninsular Malaysia, Sumatra, western Borneo and western Java (Ahmad, 2020).
 

Fig 1 : Part of a large shoal in a forest stream at Kledang Saiong Forest Reserve, Perak, Peninsular Malaysia. 

Fig 2 : Forest stream at Kledang Saiong Forest Reserve, Perak, Peninsular Malaysia. 

Fig 3 : Example from a sunlit stream issuing from a limestone cave in Perak, Peninsular Malaysia. 


References :

Ahmad, A.B. 2020. Mystacoleucus obtusirostris. The IUCN Red List of Threatened Species 2020: e.T89821023A89821039.

Fishbase - Mystacoleucus marginatus