Taxonomy & naming
Oxynoemacheilus elsae was formally described in 2018 by Soheil Eagderi, Hadi Jalili and Davut Çiçek, in the family Nemacheilidae — the stone or brook loaches, now recognised as the largest family within the loach superfamily Cobitoidea and a frequent source of newly split species as molecular work refines older, broadly-defined genera such as Nemacheilus and Noemacheilus. The genus Oxynoemacheilus itself is one of those post-split groups, erected for a cluster of small Middle Eastern and Anatolian stream loaches previously lumped into wider genera.
No older combination is recorded for this species — it was named directly in Oxynoemacheilus and has not been reassigned since. Its closest relatives are the many other small Oxynoemacheilus species scattered across Anatolia, the Caucasus and the Iranian plateau, a group whose boundaries are still being worked out species by species. The Catalog of Fishes (Eschmeyer, California Academy of Sciences) is the standing authority for the valid name; nothing here should be read as overriding it.
Morphology
This is a very small loach, reaching only about 2 in in standard length — near the small end even for a family built of small fish. Like other members of Nemacheilidae it has the typical stone-loach build: an elongate, subcylindrical body, a flattened belly suited to gripping the bottom in current, and paired fins used to brace against flow rather than to swim in open water.
Detailed morphometric and colour-pattern data beyond the original description are not available in the sources consulted here, so no attempt is made to describe fine details of banding or fin-ray counts. What can be said with confidence, because it holds across the family, is that nemacheilids are essentially scaleless or bear only tiny embedded scales, leaving the skin exposed — a trait with real consequences for how sensitive the fish is to medication and handling.
Habitat
Oxynoemacheilus elsae is known from the Zarineh River, a major tributary system feeding Urmia Lake in West Azerbaijan Province, northwestern Iran — the type locality — and has since been documented, via COI barcoding and morphometric comparison, in the Turkish portion of the adjoining Kura-Aras river system. Both drainages sit on the Iranian plateau and in eastern Anatolia, well within the wider Middle Eastern range typical for the genus.
It is a fish of fast-flowing, clear streams running over cobble and rocky substrate — cool, well-oxygenated water rather than the warm, still or blackwater conditions associated with many tropical Southeast Asian loaches. No aquarium-relevant temperature or pH range has been published for this species specifically; what is known for the genus and family points to cool-temperate stream conditions, and that is reflected cautiously in the facts below rather than invented outright.
Feeding
FishBase places Oxynoemacheilus elsae at a trophic level of 2.8, consistent with a low-level micro-predator that forages over the streambed for small invertebrates — insect larvae, small crustaceans and other benthic prey typical of fast, clear headwater and tributary reaches. This matches the general feeding pattern seen across small nemacheilid stone loaches.
No aquarium feeding records exist for this species, since it is not known to be in the hobby. Based on its wild diet and its relatives' known behaviour, a captive individual would be expected to take small live and frozen foods — bloodworm, daphnia and similar — readily, and to be reluctant with dry flake, but this is inference from the genus rather than a documented fact for elsae itself.
Mating
Nothing specific to Oxynoemacheilus elsae has been published on courtship, sexual dimorphism or spawning behaviour — this is a species known essentially only from its type description and a follow-up distributional record. No aquarium sightings or breeding observations exist to draw on.
What can be said comes from the wider pattern in Nemacheilidae: stone and brook loaches typically pair or group-spawn over open gravel in flowing water, with no courtship display or nest-building comparable to cave-guarding or mouthbrooding fishes. There is no evidence to suggest this species departs from that pattern, but equally no direct observation to confirm it.
Breeding
There are no breeding records for this species, in the wild or in captivity — it has no known presence in the aquarium trade at all. The honest expectation, based on Nemacheilidae generally, is an egg-scatterer that releases eggs over gravel and among stones in fast-flowing water, with no parental care of eggs or fry.
Stone and brook loaches as a group are rarely bred by hobbyists even where they are kept, and a species this obscure — undescribed until 2018, endemic to a specific Iranian river basin, and absent from commerce — should be assumed effectively unbred in captivity. Any keeper encountering this fish should treat breeding as unexplored territory rather than expect it to follow a documented protocol.
In the aquarium
Oxynoemacheilus elsae is not established in the aquarium hobby; there is no trade history, no common name, and no care literature specific to this species. Anything offered here is drawn from its family and genus rather than direct experience with elsae, and should be read as a starting point, not a verified protocol.
As a member of Nemacheilidae it would be expected to want cool, clear, fast-flowing, well-oxygenated water over a gravel or cobble substrate — very different from the warm, slow-flowing setups suited to many tropical loaches — and, like other scaleless loaches, to be sensitive to copper and to full-strength medication. Given its tiny adult size (around 2 in), any hypothetical aquarium housing would need to prioritise strong flow and oxygenation over sheer volume. Because it is essentially unknown in captivity, a prospective keeper should treat every husbandry detail as provisional.
Conservation
Oxynoemacheilus elsae has not been evaluated on the IUCN Red List, so it is recorded here as Not Evaluated rather than assigned a guessed category. This is unsurprising for a species described only in 2018 and known from a narrow range within the Urmia Lake basin and the adjoining Kura-Aras system.
Range-restricted stream endemics of this kind can be vulnerable to the same pressures affecting Urmia Lake's wider basin — water abstraction, damming and the drainage crisis that has affected Urmia Lake itself in recent decades — but no species-specific assessment of threats or population trend has been published for elsae. In the absence of trade or captive-breeding activity, the only conservation-relevant fact that can be stated with confidence is its Not Evaluated status and its narrow, specific home range.