Taxonomy & naming
The species was described by the Austrian ichthyologist Jakob Heckel in 1843, originally under an earlier genus combination before later authors moved it to Nemacheilus and, more recently, to Oxynoemacheilus as the Nemacheilidae were split apart on the strength of osteology and molecular work. The Catalog of Fishes — the authority for valid names — currently recognises it as Oxynoemacheilus tigris, and it belongs to the family Nemacheilidae, the stone and brook loaches, by far the largest family within the loach superfamily Cobitoidea.
Older literature and some aggregator databases still list the species under Nemacheilus tigris; that combination should be read as a synonym of the current name. The genus Oxynoemacheilus itself is a relatively recent segregate, part of the broad reshuffling of the old "Nemacheilus/Noemacheilus" catch-all genus into a number of more tightly defined Eurasian genera over the last two decades.
Morphology
Like other members of its genus, Oxynoemacheilus tigris is a small, elongate, cylindrical loach built for holding position on the bed of a flowing stream. A distinguishing feature noted for this species is a notably long, high dorsal fin with a whitish margin, which sits it apart from other stone loaches sharing its range. As a nemacheilid it lacks the erectile suborbital spine that defines the botiid loaches; instead it has the barbels and small, low-set mouth typical of a benthic micro-predator that feeds by picking at the substrate.
The skin, as in nearly all true loaches, carries only minute, deeply embedded scales and is effectively naked to the touch. This near-scaleless condition is a genus- and family-wide trait rather than something specific to this species, but it matters for anyone who might ever handle or treat the fish, since scaleless loaches absorb dissolved substances readily. Detailed morphometric data — precise maximum length, fin-ray counts, colour pattern in life — has not surfaced in the sources available for this profile; this is a genuinely data-sparse species outside of its IUCN assessment.
Habitat
Oxynoemacheilus tigris is a micro-endemic of the Queiq River drainage, a small system that rises in Turkey and historically flowed south into Syria before petering out in what was once a marshland near Aleppo. Today the species survives in a single short stretch of the river in Turkey, confined between two reservoirs, and it has been lost from the Syrian portion of its former range as that section of the river has dried up.
As a stone loach it is a fish of clear, flowing, well-oxygenated water running over sand, gravel and stone — the habitat implied by both its family and its common name. No published temperature or pH figures specific to this species were found in the sources reviewed; given its genus and setting, it should be treated as a fish of cool-to-moderate, well-aerated running water rather than warm, still or blackwater conditions, but exact figures for this particular population are not documented and should not be guessed at.
Feeding
No diet study specific to Oxynoemacheilus tigris was found in the sources consulted. Stone loaches in this genus and family are, as a rule, benthic micro-predators, foraging over the streambed for small invertebrates — insect larvae, worms, small crustaceans and zooplankton — rather than grazing algae or taking large amounts of plant matter.
Given the total absence of aquarium-husbandry literature for this Critically Endangered micro-endemic, any specific feeding regime offered here would be extrapolation rather than documented fact. The safest statement is the family-level one above: this is a small invertebrate-picker of fast, clear water, not a herbivore or a substrate-sifting detritivore.
Mating
No description of courtship, pairing behaviour or sexual dimorphism for Oxynoemacheilus tigris was located in the available sources. Nemacheilid stone and brook loaches as a group are not known for pronounced external dimorphism, and reproduction in the family generally follows a simple pattern of egg-scattering triggered by rising flow rather than any elaborate pairing ritual, but no field or captive observations specific to this species have been published to confirm details for it.
Given how narrowly the species survives — one short reach of one river, already lost from most of its historic range — even basic reproductive biology has to be treated as unknown rather than assumed.
Breeding
As with the great majority of Nemacheilidae, Oxynoemacheilus tigris is presumed to be an egg-scatterer, broadcasting eggs over gravel and stone in flowing water with no parental care, in keeping with the pattern documented across stone and brook loaches generally. No captive spawning of this species has been reported in the sources reviewed, and given its Critically Endangered status and near-total absence from the aquarium trade, it should be considered essentially unbred in captivity.
There is no evidence of any conservation breeding programme for the species in the sources consulted here. For a fish confined to a single short stretch of river between two reservoirs, that is a conspicuous and concerning gap rather than a neutral fact.
In the aquarium
Oxynoemacheilus tigris is not a fish anyone should expect to find, or keep, in the hobby. It has no meaningful presence in the aquarium trade, no husbandry literature has been published on it, and as a Critically Endangered single-river endemic it should not be collected or traded at all. What can be said comes from its family and genus: like other scaleless nemacheilids it would need clean, cool-to-moderate, fast-flowing, well-oxygenated water over a hard substrate, and — as with all near-scaleless loaches — would be highly sensitive to copper and full-strength medications if it were ever kept under veterinary or conservation-breeding care.
Any keeper who encounters this name should treat it as a conservation subject, not a stocking option: the honest posture for a species in this state is protection of its one remaining wild population, not acquisition.
Conservation
Oxynoemacheilus tigris is assessed by the IUCN Red List as Critically Endangered. It is endemic to the Queiq River drainage on the Turkey–Syria border and has already been lost from the Syrian portion of that range as the river there has dried up; the entire known wild population is now confined to a short stretch of river in Turkey sandwiched between two reservoirs. The principal threats identified are water abstraction and the desiccation of the Queiq River, compounded by drought conditions linked to climate change.
This is about as narrow and precarious a range as a freshwater fish can have: one short reach of one small river, already halved by the loss of its Syrian section, and dependent on flows that are being drawn down for human use. There is no trade pressure to speak of — the threat here is hydrological, not collection — and the species' survival is tied directly to what happens to water management in the remaining Turkish stretch of the Queiq.