Distance of the Spawning Migration of Baikal Omul Coregonus migratorius (Salmonidae: Coregoninae) in the Selenga River (Lake Baikal Basin)

The results of a study of the distribution of eggs of Baikal omul Coregonus migratorius in a large foothill watercourse in Siberia in 1935-2022 are presented. The distanse of omul spawning migration in the Selenga River (some of the migration parameters are taken into account since 1920) depends on a certain combination of abiotic environmental factors, biological parameters of spawners, timing of entry into the river, and the number of their spawning herd. The distance of migration has a high inverse correlation with the degree of maturity of the spawners, which is expressed by the maturity index of omul females, as well as with the timing of herd entry into the river and water consumption at the beginning of migration (September). The higher the maturity of the reproductive products of spawners, the shorter the migration route, and vice versa. In addition, the maturity of spawners also determines the timing (date) of stock entry into the river: less mature individuals enter the river earlier and are distributed at spawning grounds higher upstream, while more mature individuals enter the river later and spawn downstream of the river. The distance of omul spawning migration increases during a decrease in the water flow of the Selenga River in September and, on the contrary, decreases with increase in water flow. Finally, The distance of the spawning route of omul in Selenga is determined by the size of the spawning herd: the higher the number of spawners, the more area they need for spawning and the longer their spawning route. Water temperature does not influence the length of omul spawning migration. The spawning run takes place against the background of a decrease in water temperature in the river.