Taxonomy & naming
Neonoemacheilus assamensis was described by A. G. K. Menon in 1987, hence the parenthetical authority. It sits in the genus Neonoemacheilus within the family Nemacheilidae, the stone or brook loaches — by far the largest and most taxonomically unsettled of the loach families, a group that has absorbed and shed species from Noemacheilus, Nemacheilus, Schistura, Triplophysa and Barbatula as regional revisions have progressed. The Catalog of Fishes (Eschmeyer, CAS) is the standing authority for the valid combination, and it is retained here as Neonoemacheilus assamensis.
The species epithet assamensis refers to Assam, the northeastern Indian state that holds its type locality, the Pagladia River. As with many small Nemacheilidae described from single river systems in South and Southeast Asia, the genus-level history of this group has shifted repeatedly and is likely to keep doing so as regional lineages are resolved with molecular data; this account keeps the currently accepted genus rather than anticipating a future split.
Morphology
This is a small, slender-bodied stone loach, reported at a maximum of about 1.5 in standard length — one of the smaller members of an already small-bodied family. The body carries 13 to 17 dark transverse bars over a paler ground colour, and the snout bears the fleshy pad typical of Nemacheilidae, used together with barbels to probe crevices and gravel for food.
Like other nemacheilids it has an erectile suborbital spine and a body that is functionally near-scaleless — scales, where present, are tiny and deeply embedded — leaving the skin exposed and making the species sensitive to copper and to full-strength medication. Beyond the original description and the confirming range surveys, detailed morphological study of this species is sparse.
Habitat
Neonoemacheilus assamensis is known from streams with pebbly, stony bottoms in the Brahmaputra drainage of Assam, northeastern India, with its type locality in the Pagladia River. This is the classic stone-loach setting: fast-flowing, well-oxygenated, clear freshwater running over gravel and stone rather than sand or silt.
As a demersal species restricted to this kind of habitat, it depends on continuous flow and clean, oxygen-rich water; the family as a whole is intolerant of stagnant or heavily silted conditions. Detailed data on the seasonal temperature range of its home streams were not found in the sources consulted, so exact figures are given cautiously below rather than assumed.
Feeding
Neonoemacheilus assamensis is a benthic micro-predator, foraging over stone and gravel for small invertebrates — a diet consistent with its recorded trophic level of about 2.9, in the range typical of bottom-feeding Nemacheilidae that take gammarid amphipods, chironomid and other insect larvae, and similar small stream fauna.
It almost certainly hunts by working its barbels and snout pad over and between stones to locate prey hidden in the substrate, in the manner documented for related stone loaches such as Barbatula barbatula. No aquarium feeding observations specific to this species were found in the sources consulted.
Mating
No species-specific courtship or spawning behaviour has been documented for Neonoemacheilus assamensis in the sources consulted; data are sparse, as is typical for many single-river-system stone loaches. Nemacheilidae as a family are egg-scatterers rather than nest-builders or mouthbrooders, so reproduction is expected to follow the same general pattern seen across the family: no pairing bond and no courtship display beyond brief chasing at spawning.
Given the near-total absence of aquarium reports for this species, statements about sexing or seasonal triggers would be guesswork; none is offered here.
Breeding
Breeding in Neonoemacheilus assamensis follows the pattern documented for Nemacheilidae generally: eggs are scattered over gravel and among stones in fast-flowing water, with no parental care once spawning is complete. This species has not been reported bred in the aquarium, and as with most small stone loaches from a single river system, it is rarely or never encountered in the hobby at all, let alone spawned.
No water-chemistry or temperature triggers specific to this species were found in the literature searched; the data are genuinely sparse rather than simply unrecorded here.
In the aquarium
Neonoemacheilus assamensis is not an established aquarium fish, and this account should be read as a description of a wild species rather than a stocked care profile. Should it ever appear in the trade, its biology points clearly to the needs of a small, fast-water stone loach: cool-to-moderate, clear, strongly oxygenated water over a gravel or stone substrate, with good flow rather than still conditions, and a mature surface biofilm to support natural foraging.
As with all Nemacheilidae, its near-scaleless skin makes it sensitive to copper and to full-strength medications — any treatment should be dosed cautiously. Given its tiny adult size, of around 1.5 in, it would need only a modest footprint, but as a stream-dwelling species it should not be kept in still or warm stagnant water.
Conservation
Neonoemacheilus assamensis is assessed by the IUCN as Near Threatened. As a species known from a limited area of the Brahmaputra basin in Assam, its status reflects the vulnerability of a range-restricted stream fish to habitat degradation, siltation and water abstraction rather than any large, buffered population.
The species is not part of the aquarium trade, so its conservation risks are the general pressures on small South Asian hill and plains streams — pollution, damming and land-use change — rather than collection pressure. As is common for narrow-range Nemacheilidae, further field survey would help clarify its exact status and trend.