Some aspects of the reproduction of salmonid fish in the small rivers Ol’khovka and Krivoy Ruchey (White Sea drainage basin, Tersky coast of the Kola peninsula), including downstream migration of brown trout and atlantic salmon smolts, as well as the distribution of juveniles of these species across these watercourses have been studied. Data are provided on the size-weight characteristics of the parr and smolts of both species, their sex and age composition. Correlation was revealed between the progress of downstream migration and mean daily water temperature. It was established that small rivers with mean annual discharge below 1.5 m3/s harbor spawning of not only brown trout but also atlantic salmon. although the number of spawners is low (less than 20 pairs), this nevertheless contributes to enlargement of the species biodiversity. It should be borne in mind that there are hundreds of small rivers in the White Sea drainage basin, which collectively make a significant contribution to the abundance of both brown trout and atlantic salmon. The approach to surveys and studies of small watercourses should therefore be revised.