Based on a study of the morphological characteristics of the Sevang trout Salmo ischchan Kessler, 1877 acclimatized in Lake Issyk Kul (Kirghizia) and the lake form of the masu salmon Oncorhynchus masou (Brevoort, 1856) in Lake Biwa (Japan) their unique characteristics were defined. These characters allow to consider these forms as subspecies. The main directions and the rate of change of the characters with the forming of trouts and salmons in Atlantic and Pacific species in lake conditions are considered.

The original description of Salmo spurius Pallas, 1814 is based on Pallas’s own material and the literature sources, which include at least two species-group taxa. A specimen from the Gulf of Finland, deposited at Zoological Institute, St. Petersburg, is designated as neotype of S. spurius. As result of this designation, the unused name S. spurius becomes a junior synonym of S. trutta trutta Linnaeus, 1758 and does not threaten the current nomenclature of trouts from the Caspian Sea basin.