Taxonomy & naming
Neolissochilus blythii was described by the British ichthyologist Francis Day in 1870. The authority honours Edward Blyth, the naturalist and curator of the Asiatic Society of Bengal who collected and documented much of the fauna of British Burma. The species was placed in the genus Neolissochilus — a group of cyprinids closely allied to the true mahseers (Tor) and distinguished by scale and morphological characters — and that placement is retained by the Catalog of Fishes (Eschmeyer, CAS), the governing authority for valid names.
Older literature may reference the fish under different generic combinations, as Asian cyprinid taxonomy underwent substantial revision in the late twentieth and early twenty-first centuries; the Catalog of Fishes records the current valid combination as Neolissochilus blythii Day, 1870. The genus name Neolissochilus combines the Greek neo- (new) with Lissochilus, itself derived from the Greek lissos (smooth) and cheilos (lip), alluding to the smooth-lipped character used to separate the genus from related groups.
Morphology
Published size records are sparse for this species. FishBase lists a maximum standard length of 2 in, which, if accurate, would make N. blythii among the smaller members of the Neolissochilus group — a notable contrast with the largest mahseers, which can exceed a metre. The body form is presumably typical of small Neolissochilus: moderately elongate, somewhat laterally compressed, with a subterminal to inferior mouth reflecting a rheophilic, benthopelagic lifestyle in moving water.
Data on colouration, fin formula and other diagnostic characters are sparse in the available literature, and no detailed redescription appears to have been published since Day's original account. Additional field collections and morphological work would be needed to characterise the species fully.
Habitat
Neolissochilus blythii is recorded from Myanmar, specifically from the Tenasserim region in the south of the country — a hill and coastal zone drained by rivers flowing toward the Andaman Sea. The genus as a whole is strongly associated with cool, fast-flowing hill rivers and streams with rocky or gravelly bottoms, high dissolved oxygen and near-neutral to mildly acidic water, reflecting adaptation to the well-oxygenated upland rivers of South and Southeast Asia.
For N. blythii itself, detailed habitat parameters are not documented in the accessible literature, and the IUCN Data Deficient assessment reflects this gap. By analogy with congeners studied in adjacent regions, the species likely inhabits clear, current-driven hill streams at low to moderate elevations, with substrate of boulders, cobbles and gravel. Temperature ranges recorded for related Neolissochilus in comparable hill-river systems fall broadly in the range of 52–75 °F.
Feeding
No specific feeding data for Neolissochilus blythii appear in the accessible literature. Members of the genus and the broader mahseer alliance are generally opportunistic omnivores in lotic environments: they forage along the substrate and in the water column for algae, periphyton, aquatic invertebrates, fallen fruit and organic detritus, with the relative contribution of each component varying by season and locality.
The subterminal to inferior mouth typical of Neolissochilus is consistent with bottom- and surface-scraping rather than open-water predation. In fast-flowing hill streams, benthic algae, biofilm and invertebrate drift are likely the primary food sources, in keeping with the broader ecology of rheophilic cyprinids in Indochina and the Malay Peninsula.
Mating
Like all barbs, Neolissochilus blythii is an egg-scattering, non-guarding spawner. No spawning observations specific to this species have been published. In the larger mahseers and hill-stream barbs of the region, reproduction is typically seasonal and tied to monsoon-driven changes in river hydrology: rising water levels, increased turbidity and warming temperatures in the pre-monsoon and early monsoon period appear to stimulate spawning migrations toward upstream gravel beds.
A ready male pursues a gravid female through the current and over the substrate; eggs and milt are released together in brief contacts, with the adhesive or semi-adhesive eggs settling among gravel or lodging between rocks. No territory is held, no pair bond is formed, and there is no nest of any kind.
Breeding
Neolissochilus blythii has not been bred in captivity under documented conditions, and no breeding records appear in the hobby literature. The reproductive biology assumed for the species follows the egg-scattering, zero-parental-care pattern universal among barbs and the mahseer group: females broadcast adhesive eggs over gravel or rocky substrate in flowing water; neither parent guards, fans, nor tends the eggs or larvae after spawning; the eggs receive no further care and the adults do not attend the hatching site.
In congeners that are better studied, clutch sizes vary with female body size, and development is temperature-dependent. Larvae of small rheophilic cyprinids typically require well-oxygenated, flowing water in early life.
In the aquarium
Neolissochilus blythii does not appear in the aquarium trade and there are no published accounts of the fish being kept in captivity. At a maximum recorded size of 2 in SL it would be small enough for a moderately sized aquarium, but the species' association with fast, cool, highly oxygenated hill streams means that its requirements would differ substantially from those of most tropical community fish.
Were it to become available, the basic requirements for a small hill-stream Neolissochilus would include strong, well-filtered current, high dissolved oxygen, cool water (broadly mid-teens to low twenties Celsius by analogy with congeners), a gravel or pebble substrate, and the absence of slow-water or warm-water tankmates. In practice the species is unknown to horticulture and is of interest primarily to ichthyologists and specialists in Southeast Asian cyprinids.
Conservation
Neolissochilus blythii is assessed as Data Deficient (DD) on the IUCN Red List (2020). The assessment reflects a genuine absence of field data: distribution beyond the Tenasserim region of Myanmar has not been documented, population size and trend are unknown, and the ecological requirements of the species have not been characterised in the modern literature. Data Deficient is not a conservation category — it signals that a proper assessment cannot yet be made, not that the species is unthreatened.
The freshwaters of Tenasserim and southern Myanmar face a range of pressures including dam construction on major rivers, agricultural runoff, artisanal gold mining in hill streams, and increasing extraction of water for irrigation. Species with narrow endemic ranges in such systems can be vulnerable even without formal documentation of decline. Priority actions for N. blythii would be targeted field surveys to establish its current distribution, habitat requirements and population structure, which would underpin a meaningful reassessment of its conservation status.