Mesonoemacheilus is a genus of small stone loaches in the family Nemacheilidae, endemic to India and closely tied to the streams of the Western Ghats. The atlas covers 5 species, tiny fish at roughly 1.5–2.5 in, including Mesonoemacheilus herrei, the Periyar blotched loach (Mesonoemacheilus menoni), the Pambar banded loach (Mesonoemacheilus pambarensis), Mesonoemacheilus petrubanarescui, and Devi's loach (Mesonoemacheilus remadevii). Their common names track the specific rivers and hill ranges they come from, a strong sign of just how narrowly ranged these species are within the Western Ghats freshwater system.
This is a genus of scientific rather than hobby interest; it has little presence in the aquarium trade and is documented mainly through regional taxonomic and conservation surveys. The atlas records one species each as Critically Endangered, Endangered, and Least Concern, plus two Vulnerable, a heavily skewed threat profile that reflects the broader conservation picture for Western Ghats freshwater fishes, a biodiversity hotspot where small-range endemics are under sustained pressure from stream modification, water extraction, pollution, and habitat fragmentation.
Like other nemacheilids, Mesonoemacheilus species are elongate, bottom-oriented stream fish that feel their way along substrate with sensory barbels, favoring clear, flowing, well-oxygenated hill streams, exactly the kind of specialized habitat that makes them vulnerable when a stream is dammed, diverted, or degraded.