Taxonomy & naming
Rasbora bindumatoga was described by Lumbantobing in 2014 as one of four new species of the Rasbora sumatrana group, based on specimens collected from river systems in northwestern Sumatra. The description appeared in Zootaxa (volume 3764, issue 1), the primary outlet for new fish species descriptions in the region. The Catalog of Fishes (Eschmeyer, CAS) records the valid combination as Rasbora bindumatoga Lumbantobing, 2014.
The species belongs to the R. sumatrana species group, a cluster of closely related small rasboras distributed across Sumatra, the Malay Peninsula and adjacent islands. Key distinguishing characters in the original description are the presence of a black rectangular subdorsal blotch (pigmentation beneath the base of the dorsal fin), the absence of supra-anal pigmentation, and an oval basicaudal blotch. These characters collectively separate it from its congeners within the group and define its allopatric territory in coastal northwestern Sumatra.
No synonyms or subsequent reclassifications are recorded. The genus Rasbora has been substantially revised over the past two decades — many hobbyist "rasboras" have been moved into segregate genera such as Boraras, Trigonostigma, Trigonopoma, Brevibora and Rasboroides — but R. bindumatoga remains in Rasbora under current Catalog of Fishes authority.
Morphology
Rasbora bindumatoga reaches a maximum recorded standard length of 3 in, placing it at the larger end of the R. sumatrana group. Its meristic formula includes 8 dorsal soft rays and 7 anal soft rays, with a vertebral count of 32–33 — counts consistent with others in the sumatrana complex.
The diagnostic pigmentation pattern is the most useful field character: a black rectangular blotch situated beneath the dorsal fin base (the subdorsal blotch), paired with a compact oval blotch at the caudal peduncle. The absence of supra-anal pigmentation — a patch of pigment above or around the anal fin base that is present in some congeners — is a key negative character in the original diagnosis. The body form is otherwise typical of a midwater Rasbora: elongate, moderately compressed, with a pointed snout and a terminal to slightly upturned mouth suited to feeding in the water column.
Habitat
Rasbora bindumatoga is known from the Aek Sibundung, Batang Toru and Batang Gadis river systems — all draining the northwestern portion of Sumatra toward the coastal lowlands, with the Batang Toru system being a tributary flowing into the catchment associated with Lake Toba. The FishBase record describes the habitat as mountain streams and moderate-flowing turbid rivers with gravel bottoms, classed as tropical freshwater benthopelagic.
The rivers of this part of Sumatra descend from the Barisan Range and carry clear-to-turbid water depending on season and altitude. Gravel-bedded mountain tributaries in such systems tend toward cooler, moderately oxygenated water that is somewhat softer and more acidic than the lowland streams of coastal Sumatra, though the degree of blackwater influence is lower than in the Sundaland peat-swamp systems further south. The species occupies a geographically restricted range centred on a coastal strip of northwestern Sumatra, allopatric with related sumatrana-group species in adjacent drainages.
Feeding
No detailed dietary study specific to Rasbora bindumatoga has been published. Based on the ecology and feeding apparatus typical of the R. sumatrana group — an elongate, benthopelagic midwater fish with a terminal mouth — the species is expected to be an omnivorous micropredator, taking small aquatic invertebrates, insect larvae and other zooplankton from the water column, supplemented with plant material and fine organic detritus.
In an aquarium setting, fish of this size and body type from gravel-bedded Sumatran rivers typically accept good-quality flake and small granular foods readily, with frozen or live daphnia, mosquito larvae and small bloodworm helping maintain condition. Feeding behaviour at the mid-water level is characteristic of the genus.
Mating
Rasbora bindumatoga has not been bred in captivity on record and no field observations of its reproductive behaviour have been published. As a member of Rasbora — a genus of egg-scattering, non-guarding cyprinids — it is fully expected to follow the standard pattern for the group: no permanent pair bond, no nest construction and no parental care of any kind.
In related sumatrana-group rasboras, a receptive male pursues a gravid female through midwater or among plant growth, the pair pressing briefly together during which eggs and milt are released simultaneously. The adhesive to weakly adhesive eggs fall among gravel, fine-leaved plants or submerged root mats and receive no further attention from either parent. Adults in breeding condition will readily consume their own eggs.
Breeding
No captive breeding record for Rasbora bindumatoga has been documented in the accessible literature or hobby sources. By analogy with other sumatrana-group rasboras and Rasbora in general, successful spawning in the aquarium would require a separate, well-planted spawning vessel with a gravel or fine-substrate bottom over which the scattered eggs can lodge out of reach of the adults, which should be removed promptly after spawning.
Conditioning on live and frozen invertebrate foods and a slight drop followed by a rise in temperature — mimicking the onset of the wet season in Sumatran foothill rivers — is the standard trigger used for related species. Clutch sizes and development times have not been recorded for this species specifically; in comparably sized Rasbora the eggs typically hatch within 24–48 hours and larvae become free-swimming within a few days, beginning on infusoria-grade foods before graduating to newly hatched brine shrimp nauplii.
In the aquarium
Rasbora bindumatoga has not established itself in the ornamental fish trade and no husbandry accounts specific to the species appear in aquarium literature. Its collection locality — mountain and foothill rivers of northwestern Sumatra — suggests it would prefer cooler, well-oxygenated, moderately soft water with a gentle current and a gravel or fine-stone substrate, rather than the warm, tannin-stained blackwater associated with Sundaland peat-swamp rasboras.
At 3 in standard length it is a medium-sized rasbora, requiring a tank large enough for a proper shoal. Like all Rasbora it should be kept in a group of at least six to maintain natural behaviour and reduce individual stress. Should the species become available, its care requirements would likely parallel those of other mid-altitude Sumatran cyprinids: a well-filtered, aerated tank, a varied diet of quality prepared and live foods, and neutral-to-slightly-acidic water chemistry.
Conservation
Rasbora bindumatoga is assessed as Least Concern (LC) on the IUCN Red List, with the assessment dated 7 March 2020. The species is geographically restricted to river systems in coastal northwestern Sumatra — the Aek Sibundung, Batang Toru and Batang Gadis drainages — but within this range it appears to occur across multiple river systems, which likely underpins the LC rating.
Northwestern Sumatra faces ongoing deforestation and agricultural conversion in its foothill and lowland zones, and the rivers draining toward the coast are subject to sedimentation and pollution associated with palm-oil and rubber plantations in the watershed. The Batang Toru catchment in particular has drawn conservation attention as critical habitat for the Tapanuli orangutan (Pongo tapanuliensis). Continued monitoring of this restricted-range cyprinid would be prudent as land-use pressure in the watershed intensifies.