Abstract The distribution pattern of a Japanese spinous loach, Cobitis takat-suensis, was surveyed along the tributaries of four water systems (Shigenobu, Hiji, Iwamatsu and Shimanto Rivers) in Ehime Prefecture, in order to clarify the present status of the species. Local populations were found in only 18% of 259 surveyed areas (28% of 86 tributaries). The species occurred between 50-380 meters alti-tude, except in the Iwamatsu River in which lower stretches were inhabited. On-corhynchus masou ishikawae, Phoxinus oxycephalus jouyi, Zacco temminckii, Rhinogobius flumineus and R. sp.LD, which prefer mountain streams, were often found co-existing with C. takatsuensis. Judging from river basin scale and fish density, the Iwamatsu River populations were considered to be in the most critical state. Ongoing monitoring of habitat conditions, including water temperature and gravel bed status, is essential for future conservation of this endangered species.
