Structure of spawning redds, physical conditions of spawning sites and spawning season were compared between the fluvial forms of S.(O.) masou and Salv. leucomaenis in Kamidani, head water of River Yura, from 1973 to 1975. Spawning sites selectivity and redd construction pattern in S.(O.) masou are strictly limited. Spawning occurs only near the lower end of "pools (including small sluggish areas)", with constant flow and slightly inclined or approximately level stream bed composed of mainly 1-3 cm gravel. Furthermore spawning takes place rather in the lower portion of stream and in the larger pools. The construction pattern and structure of redds in Salv. leucomaenis are variable, indicating a wide selectivity for spawning sites. Spawning occurs in both the upper and lower parts of pools, where the velocity of current and the gradient of stream bed vary widely, but always with more or less whirling flow and stream bed composed of mainly 1-3 cm gravel. Moreover spawning takes place rather in the upper portion of the stream and in the smaller pools. It is clear that spawning sites selectivities of these two species differ distinctly, and their spawning sites are in most parts segregated from each other.