Data on some morphological and ecological peculiarities of the blunt-snouted lenok in the mountain Bukukunskoe Lake (Onon River basin, upstreams of Bukukun River), situated on 1800 m a. s. l. are presented. By the head length and eye diameter the lenok in this lake is determined to be close to species populations from the mountain lakes of the basins of the Bureya (Middle Amur) and Amgun (Lower Amur) rivers. In whole, fish from populations in mountain lakes differ from river ones in the Amur basin by higher values of these specific features. Differences in spawning habits are also found.