Endemic to northern and central Borneo, with records from the Malaysian states of Sarawak and Sabah, Brunei Darussalam, and the Indonesian provinces North Kalimantan (Kalimantan Utara) and East Kalimantan (Kalimantan Timur).

Type locality is ‘Kajan River, eastern slope of central Kalimantan, Indonesia [Borneo]’.

Predominantly a riverine fish preferring clear, well-oxygenated, running waters with substrates of sand, gravel, rock or mud, typically flowing through tropical forest.

In the habitat seen in our images sympatric fish species included Barbonymus balleroides, B. collingwoodi, Cyclocheilichthys repasson, C. apogon, Diplocheilichthys pleurotaenia, Garra borneensis, Leptobarbus hosii, and an unidentified Gastromyzon sp.

Substrates are generally composed of gravel, rocks, boulders or bedrock carpeted with a rich biofilm formed by algae and other micro-organisms.

At a habitat in the Mendawai river basin in central Kalimantan, H. borneensis was collected from a foothill stream running swiftly over a rock and gravel substrate with clear water of pH 6.4.

This species was considered a synonym of Channa melasoma for a number of years prior to its revalidation by Ng. et al. (1996).

Specimens larger than around 120 mm SL can be distinguished by possession of a black spot in the centre of numerous body scales and a barred caudal-fin pattern, characters which are missing in both C. melasoma and the similar-looking C. cyanospilos.

Type locality is ‘Central Sumatra, Indonesia’, with additional records existing from Cambodia (Mekong drainage), Peninsular Malaysia (Perak River), Sumatra (from the Siak River, Riau province to the Musi River, South Sumatra (Sumatera Selatan) province) and Borneo (south and westwards from the Belait river basin in Brunei Darussalam to the Sambas drainage in West Kalimantan (Kalimantan Barat) province, Indonesia and probably in Sarawak, Malaysia).

This species is variable in terms of colour. Large adults may be bright green, orange or barred but are apparently capable of changing from barred to plain in just a few seconds.

These different forms have been recorded in the same natural habitats, and some individuals also possess prominent nuptial tubercules covering much of the body.

It can be diagnosed as follows: <30 lateral scales; two black body bands reaching ventral midline posterior to anal-fin; band above anal-fin also reaching ventral midline no black band on head, though the first band may touch the posterior margin of the eye; band above anal-fin not reaching ventral midline; 6 branched anal-fin rays; 7-8 predorsal scales. Brachygobius currently contains 9 described species but is likely to prove more diverse should a review be carried out. Alt…

This species is so ubiquitous across its natural range that it’s often referred to simply as ‘common barb’. Basic adult colour pattern consists of a small, dark spot at the base of the dorsal-fin origin and another on the caudal peduncle but overall appearance varies somewhat depending on origin, with the anterior dark spot enlarged ventrally forming a bar or posterior spot extending into the caudal-fin, for example. The spots may also appear darker or lighter in some individuals.

N. selangoricus is most similar to N. spiniferus since it possesses acuminate scales above and below the lateral line on the caudal peduncle, a feature not shared with any other congener. It can however be distinguished by the following characters: presence of 8-12 very regular dark bars on flanks (vs. 10-13 irregularly-shaped bars in N. spiniferus), 3-5 times…

Field observations have revealed that individuals almost always position themselves facing into the flow, either along the sides, behind or under rocks, their specialised morphology (see ‘Notes’) allowing them to feed and maintain position without being swept away.

Not many fishes have been able to successfully colonise this narrow ecological niche, but syntopic species in nature include Gastromyzon extrorsus (Petagas River), G. introrsus, G. lepidogaster (Pad…