The cystidicolid nematode Salvelinema salmonicola (Ishii, 1916) is a parasite of freshwater salmonids in the North Pacific rim region, including Japan, Far Eastern Russia, Alaska (USA) and northern British Columbia (Canada). This species was found in the swim bladder of river-resident amago salmon (Oncorhynchus masou ishikawae Jordan and McGregor)(Salmoniformes: Salmonidae) from the Tsutsuga River and its tributary, Inomata River, of the Ota River System in Hiroshima Prefecture, western Honshu, Japan. This is the first record of S. salmonicola from western Japan, extending its distribution from central to western Honshu in the country. Oncorhynchus masou ishikawae is a new host for S. salmonicola. The life cycle of S. salmonicola and the impact of the past and current construction on the fish definitive host, invertebrate (probably amphipod) intermediate host and parasite populations in the sampling locality are discussed.