Taxonomy & naming
Oxynoemacheilus bergianus was first described in 1934 by the Russian ichthyologist Anatoly Nikolaevich Derjavin (sometimes transliterated Derzhavin), and for most of the twentieth century it circulated under a series of now-outdated combinations — Nemacheilus bergianus, Nemachilus bergianus and Orthrias bergianus among them — as the old, catch-all stone-loach genera were repeatedly split and reshuffled. The Catalog of Fishes, the standing authority for valid fish names, currently places it in Oxynoemacheilus, the genus erected for many of the stone loaches of Anatolia, the Caucasus and the Iranian plateau that were previously lumped into Nemacheilus or Noemacheilus.
The species sits within Nemacheilidae, the stone or brook loaches — by species count the largest family of true loaches, and one still being actively revised as osteological and molecular studies tease apart its many superficially similar, geographically restricted species. A 2018 osteological study (published via ResearchGate) specifically examined the phylogeny of Iranian Oxynoemacheilus bergianus, underscoring how recent and ongoing this kind of taxonomic groundwork still is for the genus. The name Oxynoemacheilus erdali is treated as a synonym of this species in Eschmeyer's Catalog of Fishes.
Morphology
Like other Nemacheilidae, Oxynoemacheilus bergianus is a small, elongate, cylindrical loach with a flattened belly suited to holding station on stream gravel, a pointed head, and small eyes set high on the skull. FishBase records a maximum length of about 3.5 in total length, in keeping with the generally modest size of stone loaches. As in its relatives, the skin carries only minute, deeply embedded scales rather than the more conspicuous body scales of many other fish groups, which in practice means the skin behaves as though nearly naked — a point that matters for how the species tolerates medications and handling.
Detailed published data on fin ray counts, barbel number and colour pattern specific to this species were not found in the cache consulted here, so those particulars are left undescribed rather than guessed at; readers wanting fine anatomical detail should consult the primary osteological literature on the species directly.
Habitat
The species is restricted to a cluster of drainages in and around northwestern Iran: the Lake Urumiyeh (Urmia) and Namak Lake basins, the southern Caspian basin from the Kura River east to the Sefid-Rud drainage, the headwaters of the Tigris where Turkey, Iraq and Iran meet, the Karoun drainage in Iran, and the headwaters of the Euphrates in Turkey and possibly into Syria and Iraq. This is a wide span of separate basins for a small stone loach, but all of them sit within the same general Anatolian–Iranian plateau region typical of the genus.
FishBase describes it as a subtropical, demersal freshwater fish of fast-flowing streams and rivers with gravel and rocky substrates, and notes specifically that it does not tolerate impoundments — still, dammed or reservoir-altered stretches of river are not habitat this species can persist in. That intolerance of slack water is the single clearest habitat fact recorded for the species and should guide any assumptions about its needs.
Feeding
No species-specific dietary study was found in the cache consulted for this article. Based on the well-documented ecology of Nemacheilidae generally, Oxynoemacheilus bergianus can be expected to behave as a benthic micro-predator, picking small aquatic invertebrates — insect larvae, worms and small crustaceans — from among the gravel and rock of the fast water it inhabits, in the manner typical of its family.
This should be read as an inference from family-level biology rather than a confirmed fact about this particular species; no aquarium feeding reports or gut-content studies specific to O. bergianus were available.
Mating
No information on sexing, courtship or spawning behaviour specific to Oxynoemacheilus bergianus was found in the cache consulted here. Stone and brook loaches as a family are typically egg-scatterers with no parental care, spawning over open gravel in fast-flowing water, and there is no reason from the available sources to expect this species to differ from that general pattern — but no direct observation of this species' mating behaviour could be confirmed, so the point is noted as inferred rather than documented.
Breeding
As with the great majority of stone and brook loaches, Oxynoemacheilus bergianus is not known to be bred in home aquaria, and it is essentially absent from the aquarium trade in the first place. Where Nemacheilidae have been observed spawning at all, the pattern is egg-scattering over gravel in flowing water with no parental care, and there is nothing in the sources consulted to suggest this species departs from that. Data on captive spawning attempts, egg counts or fry-rearing for this species specifically simply do not appear to exist in the literature reviewed here.
The honest summary is that this is a wild, little-studied stream fish rather than an aquarium-breeding subject: keepers should not expect to source captive-bred stock, and any specimens in the hobby would almost certainly be wild-collected by specialists rather than farmed.
In the aquarium
Oxynoemacheilus bergianus is not an established aquarium fish and has no meaningful trade or care history to draw on. Its recorded biology nonetheless points clearly to what it would need if ever kept: cool-to-temperate, clear, fast-flowing, well-oxygenated water over gravel and rock, with strong circulation and pristine water quality, mirroring the un-impounded mountain and foothill streams it comes from. A still, warm community tank would be the opposite of suitable habitat for a fish that FishBase specifically notes cannot tolerate impounded water.
As with other scaleless-skinned Nemacheilidae, any specimen in captivity should be treated cautiously with medications — full-strength doses and copper-based treatments are generally poorly tolerated by loaches with this kind of reduced scalation. Because it is essentially unrecorded in the hobby, anyone encountering this species should treat it as a specialist, conservation-relevant fish rather than a casual purchase, and source information from current ichthyological literature rather than assuming standard community-tank practice applies.
Conservation
Oxynoemacheilus bergianus is assessed as Least Concern by the IUCN Red List, with the assessment dated 18 March 2013 according to FishBase. Despite the reassuring category, the species' documented intolerance of impoundments is a real pressure signal: dam construction and reservoir creation across its Iranian and Anatolian range convert exactly the fast, gravel-bottomed river habitat this species depends on into still water it cannot use, and Lake Urumiyeh — one of the basins it occupies — has itself been the subject of well-known, severe water-level decline in recent decades.
The species carries essentially no fisheries or aquarium-trade profile — FishBase records it as having low vulnerability, reflecting its absence from targeted fisheries rather than any assessment of abundance trend. Its conservation story, such as it is, is tied entirely to the health of the specific river and lake basins of northwestern Iran, southeastern Turkey and adjacent Iraq that it calls home.