1.The following five species belonging to the Salmonidae are found in the rivers in Yamaguchi Prefecture. (1)Oncorhynchus keta (WALBAUM) (2)O. masou(BREVOORT) (3) O. rhodurus Jordan et McGREGOR (4) Salmo gairdnerii RICHARDSON (5) Salvelinius imbirus Jordan et Mc GREGOR The land-locked form of Salmo gairdnerii RICHARDSON which is called ”Nijimasu” were introduced into Japan from North America. 2.Oncorhynchus keta (WALBAUM)ascends the following rivers which run into the Japan Sea: the Tama, the Abu, the Misumi and the Awano. The Awano River seems to be the southern-most habitat among the rivers in the Japan Sea side. 3.Oncorhychs masou (BREVOORT) is represented by two forms: one is a sea-run form which is called ”Sakuramasu” and the other land-locked form called ”Yamame” occuring in the upper reaches of rivers.