Freshwater-fish fauna of the Minami River system, Reinan Region, Fukui Prefecture, Japan, was investigated in 1998. Forty-five species in 14 families (including those newly recorded, such as Rhinogobius flumineus) were identified in the present research. Combined with data previously reported, a total of 55 species in 16 families, which included 36 primary and diadromous freshwater species (11 families), composed the fish fauna that could be considered naturally distributed in this river system. Compared to the richer fish fauna in western Japan regions, that of the Minami River system, representative of the Reinan Region, is poorer, and composed of peripheral fish fauna. The construction of many weirs and dams along the river system have prevented fish migration, causing more or less distinct fish assemblages to form in each of the upper, middle and lower reaches. Also, a number of species which inhabit small tributaries and/or irrigation channels in the Minami River System, such as Tanakia limbata, Acheilognatus tabira subsp.1 (sensu Hosoya, 1993), Lefua echigonia, Oryzias latipes, and the `nagare-hotokedojo'L. sp.(sensu Hosoya, 1993), have been threatened with extinction.
