Nemacheilidae

Nemacheilidae, commonly known as stone loaches, are a family of small to medium-sized freshwater fish in the order Cypriniformes. They are primarily benthic, inhabiting fast- to moderately flowing streams with gravel or rocky substrates across Europe and much of Asia.

Taxonomy and classification: Nemacheilidae comprises multiple genera, including Schistura, Nemacheilus, Barbatula, Oxynoemacheilus, and Triplophysa. They were previously treated as a subfamily within Balitoridae, but are now recognized as a distinct family within the superfamily Cobitoidei.

Description and ecology: Stone loaches are elongated, bottom-dwelling fishes. Many species have barbels around the mouth, a flattened ventral surface, and a slender body adapted to clinging to substrates in fast-flowing water. They are typically small, with common species measuring 2–10 cm, though some reach larger sizes. They feed mainly on small invertebrates and algae, foraging along the substrate and among stones.

Distribution and habitat: They occur widely across Europe and Asia, from European Russia to Southeast Asia, with hot spots in the Himalayas and Mesopotamian river systems. They prefer clean, well-oxygenated water and substrates of gravel, rocks, or cobble; many species inhabit riffles and run habitats.

Reproduction and conservation: Most Nemacheilidae are egg-layers that deposit adhesive eggs among gravel or vegetation; parental care is rare. The family faces threats from habitat degradation, siltation, pollution, and damming of rivers. Some species have restricted ranges and are listed as threatened by conservation organizations. They are also popular in the aquarium hobby, particularly Asiatic species such as Schistura and Barbatula, and are used as indicators of stream health.