Taxonomy & naming
Oxynoemacheilus kaynaki was described in 2008 by Turkish ichthyologists Fahrettin Erk'akan, S. Cihangir Özeren and Turhan Nalbant, part of a wave of new Oxynoemacheilus species that followed the splitting of the old, catch-all genus Noemacheilus/Nemacheilus into a set of narrower Palearctic and Anatolian genera. The Catalog of Fishes lists no earlier or alternative combination for this species — it was named directly into Oxynoemacheilus and has stayed there, with no synonymy to untangle.
The species epithet honours Hüseyin Kaynak, the father of the senior author, a dedication rather than a description of the fish itself. It sits in the family Nemacheilidae, the stone or brook loaches, within the loach superfamily Cobitoidea — a family that has absorbed an enormous number of newly described, narrow-range species from mountain streams across Anatolia, the Caucasus, Iran and Central Asia over the last two decades, of which this is one.
Morphology
Oxynoemacheilus kaynaki is a small, slender stone loach, reaching only about 3 in in total length — modest even by the standards of this family. Diagnostic features recorded in the original description and subsequent database entries include 9–10 branched dorsal-fin rays, 15–17 branched caudal-fin rays, a convex (rounded, not forked) caudal fin, and a distinctive marking at the base of the tail. Like other nemacheilids it has a slim, near-cylindrical body suited to holding position against current, small eyes set high on the head, and barbels around the mouth for feeling out food on the streambed.
No aquarium-specific description of colour pattern or sexual differences has been published; what is known comes entirely from preserved museum specimens used for the original taxonomic description, archived and available for verification through taxonomic treatment repositories.
Habitat
The species is known from the Göksu River drainage in south-eastern Anatolia, Turkey, a tributary system of the upper Euphrates at roughly 38°N. This places it in a temperate mountain-and-plateau freshwater system, not a tropical one — the kind of clear, fast-flowing, cobble-and-gravel stream typical of Anatolian headwaters, classified in the literature as a demersal (bottom-dwelling) freshwater fish.
No direct temperature or pH measurements have been published for the type locality, but the setting — a temperate SE Anatolian river fed by mountain runoff — points to a cool, well-oxygenated stream rather than a warm lowland one, likely in the range of roughly 54–68 °F through the year, with the alkaline, mineral-buffered water typical of limestone-influenced Anatolian catchments. This is an honest inference from the habitat type, not a measured figure, and should be treated as approximate.
Feeding
FishBase records a trophic level of 2.8 for this species, consistent with a benthic micro-predator/omnivore rather than a herbivore or detritivore. In practice this means it forages over the stream bottom for small aquatic invertebrates — insect larvae, small crustaceans and similar prey — picking through gravel and cobble rather than grazing algae or biofilm.
No aquarium feeding data exists for this species. Based on its trophic ecology and its close relatives among the stone loaches, it would be expected to take small sinking live and frozen foods (bloodworm, brine shrimp, chopped invertebrates) readily, with limited interest in flake or plant-based foods — but this is an inference from the genus, not a documented observation of the species itself.
Mating
No courtship or spawning behaviour has been recorded for Oxynoemacheilus kaynaki, and there is no sexual dimorphism described in the literature — no published difference in colour, fin shape, or body form between presumed males and females. This is unsurprising for a species known mainly from a taxonomic description rather than field or aquarium observation.
What can be said comes from the genus and family as a whole: Nemacheilidae stone loaches are egg-scattering fish with no courtship display of the kind seen in cichlids or livebearers, and spawning in wild stone loaches is generally tied to seasonal rises in flow and temperature that trigger ripening. There is no reason to expect this species differs from that pattern, but it has not been documented.
Breeding
As with the great majority of Nemacheilidae, Oxynoemacheilus kaynaki is best assumed to be an egg-scatterer: females release eggs over gravel and among stones in fast-flowing water, with no parental care of eggs or fry. This is the standard breeding mode across the stone and brook loaches, in clear contrast to the cave-guarding males of gobies or the mouthbrooding seen in some cichlids — nothing like either occurs in this family.
There is no record of this species being bred, or even maintained, in captivity. It is not part of the aquarium trade, and the data are simply too sparse to say more than that it likely follows its relatives: egg-scattering, no parental care, and — realistically — rarely or never spawned outside its native stream.
In the aquarium
Oxynoemacheilus kaynaki is not an aquarium fish in any practical sense. FishBase and the other sources consulted here record no husbandry data at all — no tank reports, no keeper accounts, no photographs of live specimens in captivity. It appears to be essentially unknown outside of scientific collections and taxonomic literature, a common situation for narrow-range Nemacheilidae described from a single river system.
If it were ever kept, general stone-loach logic would apply: cool, clean, fast-flowing, well-oxygenated water over a gravel or cobble substrate, sized appropriately for a fish that tops out around 3 in. Like other loaches it is likely near-scaleless and correspondingly sensitive to copper-based medications and full-strength treatments, a point worth flagging even though it has not been tested in this species specifically. For now, this is a fish for the scientific record rather than the fish room.
Conservation
The IUCN Red List assessed Oxynoemacheilus kaynaki as Least Concern in January 2013. Occurrence data are limited to the Göksu drainage in south-eastern Turkey, and the species is not reported to be under any specific documented pressure, but as with many narrow-range Anatolian stream fishes, its entire known range is a single river system, which leaves comparatively little buffer against local habitat change such as water abstraction, damming or pollution.
There is no evidence of this species being collected for the aquarium trade — it is effectively absent from hobby channels — so any conservation concern would stem from habitat pressures on the Göksu/Euphrates system itself rather than from ornamental collection.