Taxonomy & naming
Oxynoemacheilus seyhanensis was described by the Romanian ichthyologist Petru Bănărescu in 1968, placing it in the genus that would later be recognized as Oxynoemacheilus Bănărescu & Nalbant, 1966 — one of several genera carved from the old, broad Nemacheilus/Noemacheilus over the second half of the twentieth century as the Palaearctic stone loaches were revised in detail. A related nominal species, Oxynoemacheilus kosswigi (Erk'akan & Kuru, 1986), has since been shown to be a junior synonym of O. seyhanensis, a taxonomic clarification reflected in the modern literature.
The species sits in family Nemacheilidae, the stone or brook loaches, by far the largest and most species-rich loach family, spread across Eurasia from Anatolia and the Middle East through Central Asia and the Himalaya to East and Southeast Asia. Within that sprawl, Oxynoemacheilus is the western Palaearctic genus, concentrated in Anatolia, the Levant and the wider Middle East, with many of its member species narrowly restricted to single river drainages — a pattern O. seyhanensis exemplifies.
Morphology
As in other Nemacheilidae, the body is small, elongate and nearly cylindrical, built for holding position on the bed of a running stream rather than for open swimming. Reported maximum length is modest — around 3.5 in total length — putting it at the small end even for a stone loach. Scientific surveys of Anatolian populations (specimens of roughly 2–2.5 in standard length from streams such as the Soruk, Zamantı and Pınarbaşı) have documented high morphological variation across 26 measured traits, suggesting the populations across its range have diverged somewhat from one another — consistent with a species whose populations are separated into distinct, disconnected stream systems.
As with its relatives in the family, the near-scaleless skin typical of nemacheilids leaves the fish sensitive to medication and to rough handling, and the small erectile suborbital spine characteristic of true loaches (Cobitoidea) should be assumed present, though it is far less conspicuous than in the spined botiid loaches. Colouration and fine anatomical detail are not well documented in the available sources; this is a plainly-marked, camouflaged stream fish rather than a showy one.
Habitat
Oxynoemacheilus seyhanensis is endemic to Turkey, known from the Seyhan River system and from the Kızılırmak and Yeşilırmak drainages of central and southern Anatolia. Its type locality lies between Viranşehir and Kazancık. These are freshwater, subtropical streams and rivers of the Anatolian plateau and its margins — benthopelagic water, meaning the fish holds close to the bottom in the flowing water column rather than in still, complex vegetation.
No specific temperature or pH range has been documented in the available sources, but the genus as a whole, and the Anatolian stone-loach fauna in particular, is associated with cool-to-mild, clear, well-oxygenated, fast-flowing streams rather than warm, still, blackwater habitats. Given the altitude and continental climate of its central-Anatolian range, this is best treated as a cool-temperate to subtropical running-water species, not a warm tropical one.
Feeding
FishBase places Oxynoemacheilus seyhanensis at trophic level 2.8, consistent with an omnivorous diet — a mix of small invertebrates and organic matter picked from the streambed, in keeping with the micro-predatory, bottom-foraging habit typical of stone loaches. Detailed dietary studies specific to this species are not available in the sources consulted.
In an aquarium built to its habits, a diet modelled on that of other Nemacheilidae is the safest approach: small sinking foods — fine pellets, frozen bloodworm or daphnia, and other small live or frozen invertebrate foods — offered at the bottom, where this fish naturally forages. Flake that sits at the surface is unlikely to be taken reliably.
Mating
No courtship or spawning behaviour has been documented for Oxynoemacheilus seyhanensis in the sources available, and this is honestly typical for a narrow-range Anatolian stone loach known mainly from taxonomic and morphometric surveys rather than from long-term field or aquarium observation. Sex-specific dimorphism is not described in the available literature.
What can be said comes from the broader biology of Nemacheilidae: stone and brook loaches are egg-scatterers, releasing eggs over gravel and among stones in flowing water with no pair bond and no nest, rather than forming pairs that guard a site.
Breeding
Data on captive or wild breeding of this species specifically is sparse to non-existent in the sources reviewed. Consistent with its family, the expected mode is that of a typical stone/brook loach: an egg-scatterer that releases eggs over gravel or among stones in fast-flowing water, with no parental care of eggs or fry. There is no indication of cave-guarding, mouthbrooding, or any elaborate parental behaviour — those belong to other fish groups entirely, not to Nemacheilidae.
This species is not established as an aquarium-bred fish; it is essentially unknown in the hobby, and what little is documented about it comes from field surveys of its native Turkish streams rather than from spawning attempts in captivity. A keeper should not expect to breed it, and any claim of captive breeding should be treated with caution absent a documented source.
In the aquarium
Oxynoemacheilus seyhanensis is not a fish of the ornamental trade — it does not appear to be commercially available, and the material behind its description comes from scientific collecting in its native rivers rather than from aquarium stock. Anyone encountering it, whether through specialist collectors or future availability, should treat it as a cool-water, fast-flow stream species: well-oxygenated, moving water, a gravel or mixed sand-and-stone substrate, and stable, clean conditions rather than a warm, static community setup.
As with other Nemacheilidae, assume a near-scaleless skin sensitive to copper-based medications and full-strength treatments generally — half-doses and gentle products are the safer default for any stone loach if disease treatment becomes necessary. Given its small maximum size (under 4 in), a modestly sized, well-filtered, current-carrying aquarium would suit it, but with no established husbandry record this remains a matter of applying general loach principles rather than species-specific experience.
Conservation
Oxynoemacheilus seyhanensis is assessed as Critically Endangered (CR) on the IUCN Red List, an assessment dated 14 January 2013, with habitat loss cited as the principal threat. This tracks a broader pattern among Anatolian stone loaches restricted to single or few river systems: narrow endemism leaves a species with essentially nowhere to retreat if its home streams are degraded, dammed, diverted, or polluted.
The species' entire known range sits within Turkey's Seyhan, Kızılırmak and Yeşilırmak systems — rivers subject to damming, water abstraction for agriculture, and other anthropogenic pressures common across central Anatolia. There is no indication that the aquarium trade plays any role in its conservation picture; the threats documented are habitat-driven, not collection-driven. As a Critically Endangered, non-traded, single-country endemic, its future depends entirely on the condition of a small number of specific Turkish rivers.