Taxonomy & naming
Neolissochilus nigrovittatus was described by George Albert Boulenger in 1893. Boulenger was a prolific Belgian-British ichthyologist at the Natural History Museum, London, responsible for describing a large proportion of the freshwater fishes of tropical Asia and Africa during the late nineteenth and early twentieth centuries. The species epithet nigrovittatus is Latin for 'black-striped' or 'black-banded', referring to a prominent lateral marking.
The genus Neolissochilus was erected to accommodate a group of large cyprinids from South and Southeast Asia that were long merged into the sprawling old genus Tor or Barbus. They are sometimes called the Southeast Asian mahseers, though Neolissochilus is now treated as a genus distinct from the true mahseers of the genus Tor. The Catalog of Fishes (Eschmeyer, California Academy of Sciences) recognises the valid combination as Neolissochilus nigrovittatus Boulenger, 1893, with no parenthetical authority, indicating the species has remained in the genus it was originally described in.
Older references may place this fish in Barbus or Tor; current ichthyological practice follows the Catalog of Fishes in retaining it within Neolissochilus.
Morphology
Neolissochilus nigrovittatus is a moderately large barb, reaching a maximum recorded total length of around 5 in per FishBase, though large-river mahseers in the Neolissochilus group can attain considerably greater sizes under favourable conditions. The body form is elongate and robust in the manner typical of fast-water cyprinids, with strong musculature suited for holding position in current.
Specific colouration details for this species are not well documented in the accessible literature. The species name references a dark longitudinal band or stripe, which is a common feature in stream-dwelling Southeast Asian barbs and cyprinids and likely functions in schooling behaviour or camouflage against dappled streambed light. As with other Neolissochilus, it is presumed to be sexually dimorphic, with females becoming notably fuller-bodied when gravid, though no detailed morphometric or colour dimorphism data are available for this species specifically.
Data on body proportions, scale counts, fin-ray formulae and other meristic characters are documented in the original description by Boulenger (1893) and in subsequent revisions of the Neolissochilus group.
Habitat
Neolissochilus nigrovittatus is native to freshwater river systems in Myanmar and Thailand, where it occupies fast-flowing, well-oxygenated hill streams and mountain rivers. FishBase categorises it as benthopelagic, indicating it inhabits both mid-water and the vicinity of the riverbed. Streams within the Neolissochilus group's range typically have rocky or gravelly substrates, clear water of high transparency, and elevated dissolved oxygen levels maintained by rapid flow and turbulence.
The genus Neolissochilus is potamodromous — capable of substantial upstream migrations for reproduction, sometimes exceeding 75 mi — and individual species are strongly associated with particular river catchments or highland drainage systems. Water temperature in the hill-stream habitats of Myanmar and Thailand varies seasonally, tending cool in upland reaches. The broader Neolissochilus group favours neutral to slightly alkaline, moderately hard water conditions; precise temperature and pH data specific to N. nigrovittatus have not been published in the accessible literature.
Sensitivity to habitat degradation is characteristic of the group: siltation, dam construction, water abstraction and loss of riparian forest canopy — which moderates water temperature and delivers invertebrate food — all degrade the cool, clear, fast-flowing conditions these fishes require.
Feeding
Neolissochilus species are generally regarded as opportunistic omnivores of running-water environments. Riverine mahseers in this group are known to consume benthic invertebrates including insect larvae, crustaceans and molluscs, as well as algae, periphyton, and organic detritus scraped from rocks and the substrate. Larger individuals may also take small fish and terrestrial insects that fall onto the water surface.
Specific dietary studies on N. nigrovittatus have not been located in the accessible literature; the feeding ecology described here is inferred from the group's general biology and the benthopelagic habitat designation from FishBase. The riverine fast-water environment is food-rich for fishes adapted to exploit the algal biofilm on rocks, the invertebrate community in the interstices of gravel and cobble, and the drift of invertebrates carried downstream.
Mating
Like all barbs and cyprinids, Neolissochilus nigrovittatus is an egg-scattering, non-guarding spawner. The Neolissochilus group as a whole is potamodromous, meaning that spawning migrations upstream into cooler, faster-flowing headwaters are the probable reproductive strategy, as documented for related mahseer species.
Courtship follows the pattern typical of large river barbs: a driving male pursues a gravid female through the current or over the substrate, and the pair releases eggs and milt together in brief contact. There is no pair bond, no territory held beyond the moment of spawning, and no parental behaviour. Seasonality of spawning is likely tied to the monsoon cycle and associated temperature and flow changes in the river systems of Myanmar and Thailand, as is characteristic of migratory cyprinids across the region.
Breeding
No published accounts of successful captive breeding of Neolissochilus nigrovittatus have been located. Like other large river barbs and mahseers, the species would be an egg-scatterer broadcasting adhesive or semi-adhesive eggs over clean gravel and cobble in flowing water, with no parental care whatsoever — adults do not guard, tend, or attend the eggs or larvae.
The general reproductive pattern inferred for the species involves seasonal upstream movement to spawning grounds in headwaters or fast-riffle reaches, a behaviour documented in other potamodromous Neolissochilus species. The eggs and newly hatched larvae drift or settle among substrate interstices, where current keeps them oxygenated. Juveniles likely rear in shallow, vegetated margins or slower side-channels before recruiting to adult habitat. No aquarium-breeding information is available for this species.
In the aquarium
Neolissochilus nigrovittatus is not established in the ornamental trade and is essentially unknown in the aquarium hobby. No captive-husbandry data — tank size requirements, preferred water chemistry, behaviour in captivity, compatible species, or diet — are available in the accessible literature.
Based on the biology of the genus, any successful maintenance would require conditions that replicate the cool, fast, highly oxygenated rivers of the Myanmar–Thailand uplands: powerful filtration and circulation, very clean, well-oxygenated water, a rocky or gravelly substrate, and cool temperatures. Large mahseers and their relatives typically grow too large for most home aquaria and are poorly suited to captive life in the absence of specialist facilities. This species is best regarded as a wild river fish of scientific and conservation interest rather than an aquarium subject.
Conservation
Neolissochilus nigrovittatus is assessed as Data Deficient (DD) on the IUCN Red List, a status assigned in February 2011. The Data Deficient classification reflects an absence of adequate information to evaluate the species' population size, trend, or distribution in sufficient detail to assign a threat category — not a conclusion that the species is secure. Given the paucity of surveys in its Myanmar and Thailand river drainages, the true conservation situation is unknown.
The freshwater ecosystems of Myanmar and Thailand face a range of pressures that are well documented across the region: hydroelectric dam construction on major rivers and their tributaries, widespread siltation from upland deforestation and agriculture, water extraction for irrigation, and pollution from mining and agricultural run-off. Neolissochilus species as a group are sensitive to these changes because they depend on the clear, fast, cool, structurally complex streams that are among the first habitats to be degraded. The potamodromous behaviour of the group — requiring unimpeded access to headwater spawning grounds — makes dams a particularly acute threat.
A comprehensive assessment of this species' status would require targeted surveys in its native river systems, genetic analysis to clarify population structure, and monitoring of catchment-level land use and hydrology.