Population abundance of Dolly Varden in streams of the Shiretoko Peninsula, Hokkaido, in relation to water temperature warming was investigated.  Among the salmonid fishes in the region, Dolly Varden is the only stream resident species throughout the life and is an important ecosystem component.  The fish abundance and stream temperatures were surveyed in 37 streams from 1999 to present.  Almost all of the streams were inhabited by Dolly Varden and some had extremely high densities >80 ind. per 100 m^2.  However, several populations had <5 per 100 m^2 and suffered from summer temperature warming where the values exceeded the species' thermal maxima of foraging being 20-22˚C and were even closer to the mortality being 24˚C.  These streams also showed signs of recruitment failures among years.  Such streams were characterized by having shallower and slower current as well as less riparian forest associated with the construction of sediment-control dams.  It was also intriguing that water temperatures increased in a long time trend in some streams but decreased in several others due to unknown causes despite that the air temperatures in the region have continually increased in the past.  Future riparian and dam management will be crucial for conservation of Dolly Varden.