Taxonomy & naming
Oxynoemacheilus evreni was described in 2007 by Turkish ichthyologists Fahrettin Erk'Akan, Türker Nalbant and Salim Özeren, part of a wave of Anatolian stone-loach descriptions from that research group in the 2000s that greatly expanded the known diversity of Turkey's freshwater fish fauna. It sits in the genus Oxynoemacheilus, a group of small stone loaches found across Anatolia and the wider Middle East, within the family Nemacheilidae — the true stone or brook loaches, by far the largest family in the loach superfamily Cobitoidea.
Genus-level taxonomy in this part of Cobitoidea has been reworked repeatedly: many species once lumped into a broad Nemacheilus or Noemacheilus have since been redistributed among Oxynoemacheilus, Schistura, Triplophysa, Barbatula and other genera as researchers resolved the group with more detailed anatomical and molecular study. The Catalog of Fishes is the reference point for the currently valid combination, and it places this species in Oxynoemacheilus. No synonymy or reclassification affecting this particular species is noted in the cached record.
Morphology
Like other members of its genus, Oxynoemacheilus evreni is a small, slender, elongate loach built for life on the bed of a fast-flowing stream — a low-slung, bottom-hugging body shape shared across Nemacheilidae. Species-specific measurements, colour pattern and fin-ray counts for O. evreni are not available from the sources consulted here, so no size or pattern claim beyond the genus norm should be assumed.
As in other Oxynoemacheilus and related stone loaches, an erectile suborbital spine below the eye and a covering of very small, deeply embedded scales are typical of the group; the skin effectively reads as near-scaleless, which matters for how the fish should be handled and medicated. Precise confirmation of these features for this exact species would require the original description, which was not part of the cached research for this article.
Habitat
Oxynoemacheilus evreni is endemic to Turkey, part of the country's remarkable diversity of small, range-restricted stone loaches that each occupy their own stream system or drainage in Anatolia. As with its congeners, it is expected to live in cool-to-cool-temperate, clear, fast-flowing, well-oxygenated water over gravel and stone substrate — the classic stone-loach habitat, quite different from the warm, slow blackwater favoured by many tropical aquarium fish.
The precise river system, elevation and water chemistry of the type locality are not detailed in the sources available, and the species should be treated as a narrow-range stream endemic unless and until fuller distribution data comes to light.
Feeding
Stone loaches in this genus are bottom-dwelling micro-predators, picking small aquatic invertebrates — insect larvae, small crustaceans and other invertebrate prey — off gravel and stone in fast-flowing water. Oxynoemacheilus evreni is expected to follow this pattern typical of Nemacheilidae, though no diet study specific to the species was found.
In an aquarium setting modelled on the genus, small sinking live and frozen foods (bloodworm, daphnia, brine shrimp) would suit this feeding style far better than floating flake, which a bottom-oriented micro-predator like this is likely to ignore.
Mating
No species-specific information on courtship, spawning triggers or sexual dimorphism in Oxynoemacheilus evreni was found in the cached research. Stone and brook loaches in Nemacheilidae generally show little obvious external dimorphism and are not known for elaborate courtship; spawning in the group is typically a simple release of eggs over gravel in flowing water rather than any pair-bonding or nest-building behaviour.
Breeding
As is typical for Nemacheilidae, Oxynoemacheilus evreni is presumed to be an egg-scatterer, releasing eggs over gravel or among stones in fast-flowing water with no parental care afterward — the same pattern documented across the genus and family. This is a very different reproductive strategy from the cave-guarding males of gobies or the mouthbrooding seen in some cichlids, and none of that behaviour applies here.
This species has no documented aquarium-breeding record, and stone loaches of this genus are rarely if ever bred in home tanks. Given how little is published on it even outside the aquarium, breeding should be considered essentially undocumented rather than simply difficult.
In the aquarium
Oxynoemacheilus evreni is not established in the aquarium trade — the cached research found no hobbyist profiles, retailer listings or care reports for it, consistent with it being a narrow-range Turkish endemic collected, if at all, only for scientific survey work rather than the ornamental trade. Anyone who did encounter it should default to genus-typical care: cool, clean, fast-moving, highly oxygenated water over a gravel or stone substrate, since this is a stream fish, not a warm, still-water species.
As with other small nemacheilids, the near-scaleless skin typical of the group means caution with copper-based medications and full-strength treatments would be prudent if this species were ever kept, and — as with most stone loaches — it should not be assumed to tolerate warm tropical community-tank conditions.
Conservation
Oxynoemacheilus evreni has not been evaluated by the IUCN Red List; its status here is recorded honestly as Not Evaluated rather than guessed at. Many of Turkey's numerous endemic Oxynoemacheilus species — often known from a single stream or small drainage — remain unassessed or are listed as Data Deficient, and this species appears to fall into that same gap in global conservation assessment.
Without a formal assessment, specific threats to this species cannot be stated with confidence, though Anatolian stream endemics of this kind are broadly exposed to the same regional pressures as other narrow-range freshwater fish: water abstraction, damming and habitat alteration in their home drainages. It is not part of the aquarium trade, so collection pressure is not a relevant concern for it.