Taxonomy & naming
Rasbora maninjau was formally described by Lumbantobing in 2014 from specimens collected in Lake Maninjau, West Sumatra. The species epithet is a direct toponym: maninjau references the lake that is both the type locality and the entirety of the known native range. The Catalog of Fishes (Eschmeyer, California Academy of Sciences) is the governing authority for the valid name, which stands as Rasbora maninjau Lumbantobing, 2014.
The genus Rasbora is one of the largest and most taxonomically complex genera in the family Cyprinidae. Over recent decades several satellite genera have been carved out — Boraras, Trigonopoma, Brevibora, Kottelatia and Rasboroides among them — and the boundaries of Rasbora sensu stricto remain a subject of ongoing revision. Rasbora maninjau is placed in Rasbora in the current Catalog of Fishes, and that placement is followed here. No significant synonymy is on record for this recently described species.
Locally, the fish is grouped under the vernacular bada, a West Sumatran market and fishing term applied to small rasboras from Lake Maninjau that is used across several related species in the same lake system.
Morphology
Rasbora maninjau is a slender, laterally compressed cyprinid. FishBase records a maximum standard length of 3.5 in SL, making it a mid-sized member of the genus. Field size-distribution data from Lake Maninjau show naturally occurring fish ranging from roughly 0.5 in to 5 in total length across the seasons, with weights spanning 1.8 to 14 g, suggesting the population contains a wide size range at any given time of year.
Detailed colour and fin descriptions from the original description are not captured in the available data; the species shares the general rasbora bauplan of a streamlined, silvery body suited to open-water schooling in a lake environment. As with other Rasbora species, sexual dimorphism is subtle and most readily apparent in gravid females, which develop a noticeably deeper, rounder abdomen.
Habitat
Lake Maninjau is a caldera lake of volcanic origin lying at approximately 1512 ft elevation in the Agam Regency of West Sumatra, Indonesia. It is one of the larger lakes in Sumatra, with a surface area of roughly 62 mi² and considerable depth, occupying a collapsed volcanic crater basin in the Bukit Barisan mountain chain.
Water chemistry sampled from the lake in the natural habitat of Rasbora maninjau records temperatures of 77–83 °F, pH of 5.5–6.4, and dissolved oxygen of 4.9–6.2 mg/L — conditions that define a warm, mildly acidic freshwater system. The substrate is described as sand to gravel. This is a clearwater crater lake, not a blackwater peat-swamp system, though the mild acidity reflects the region's geology and soft rainfall-fed hydrology. Rasbora maninjau is benthopelagic and is found throughout the lake's water column in social aggregations typical of the genus.
Feeding
FishBase assigns Rasbora maninjau a trophic level of 3.2 ± 0.4, placing it solidly in the category of a small invertebrate feeder — a micropredator that targets small aquatic invertebrates, insect larvae and similar zooplankton-scale prey, with some contribution from plant material and detritus at the margins of its diet. This is the typical feeding niche of small Rasbora species in lentic environments.
In Lake Maninjau itself, these fish are part of the local artisanal fishery as bada, implying they occur in sufficient abundance to be commercially harvested — a population-level fact that also reflects the availability of suitable prey resources within the lake. In an aquarium context, the species would be expected to accept a wide range of small live and frozen invertebrate foods alongside quality dry foods.
Mating
Rasbora maninjau, as a member of the family Cyprinidae and the genus Rasbora, is an egg-scattering, non-guarding spawner. No nest is constructed and no parental care is provided after spawning. Courtship follows the pattern typical of the genus: a driving male pursues a gravid female through open water or vegetation, and eggs and milt are released together in brief, close contact.
Spawning in lake-dwelling rasboras is generally tied to seasonal cues — shifts in water temperature, rainfall input, or photoperiod — rather than the monsoon flooding cycle that triggers spawning in many stream-dwelling cyprinids. Specific breeding seasonality for Rasbora maninjau in Lake Maninjau has not been detailed in the available literature; the lake's relatively stable thermal conditions (77–83 °F year-round) may moderate the seasonal signal compared with stream-dwelling relatives.
Breeding
Like all rasboras, Rasbora maninjau scatters adhesive eggs over plants, moss or substrate and provides no parental care whatsoever; adults will readily consume eggs given the opportunity. In captivity the standard approach for egg-scattering rasboras applies: a separate spawning vessel with fine-leaved plants or spawning mops, a well-conditioned pair or small group, and removal of adults immediately after spawning.
No captive breeding record for Rasbora maninjau is documented in the available data, which is unsurprising given how recently (2014) the species was described and how limited its availability in the trade is likely to be. Fertilised eggs would be expected to hatch within two to three days at tropical temperatures, with larvae becoming free-swimming shortly after and accepting infusoria and then nauplii once feeding begins.
In the aquarium
Rasbora maninjau is a rarely encountered species in the ornamental trade. Its status as a very recently described endemic — known only from a single lake in Sumatra — means captive specimens are unlikely to be widely available, and collection from the wild is complicated by its Endangered status. Serious hobbyists who do obtain this species should treat it as a conservation priority and direct effort toward establishing a sustainable captive population.
The water chemistry of Lake Maninjau points toward warm (77–82 °F), mildly acidic (pH 5.5–6.4), soft to moderately soft water for keeping this species. A well-planted aquarium with open swimming space and good oxygenation would reflect the clearwater, sand-to-gravel lake conditions it inhabits. As with all rasboras, it is a social species best maintained in a group of at least six to eight individuals.
Conservation
Rasbora maninjau is assessed as Endangered (EN) on the IUCN Red List, assessed in April 2020 under criteria B1ab(i,ii,iii)+2ab(i,ii,iii). These criteria reflect a species with a very small estimated extent of occurrence and area of occupancy — in this case a single lake basin — combined with documented or inferred continuing decline in the quality and extent of its habitat.
Lake Maninjau has experienced severe water-quality deterioration in recent decades, driven primarily by intensive cage aquaculture (fish farming on floating net cages), which has caused eutrophication, periodic mass fish kills from oxygen depletion, and accumulation of organic waste on the lake floor. Catchment deforestation adds nutrient runoff and sedimentation. For a species endemic to this lake alone, with no alternative refuge population anywhere else in the world, these pressures represent a direct and ongoing existential threat. Conservation of Rasbora maninjau is inseparable from the broader management of Lake Maninjau's water quality and catchment land use.