Studies of the Water Discharge Effect on the Spawning Migration Distance of Baikal Omul Coregonus migratorius (Coregonidae) in the Selenga River Based on Long-term Data

Author:

Bazov A. V., ,Bazova N. V.,Frolova N. L., ,

Abstract

The Selenga River, the main tributary of Lake Baikal, is 1,453 km long and accounts for 50 % of its surface runoff. It is a large foothill, free-flowing, unregulated watercourse flowing through Mongolia (2/3 of the length) and Russia (1/3). Global climatic changes in recent decades have been particularly evident in the Baikal region: since the mid-1990s, there has been a significant decrease in water and sediment runoff in the Selenga basin. Omul spends most of its life cycle in the lake; spawning takes place in the river system. In total, there are 22 spawning rivers of Baikal omul in the Lake Baikal basin, among which 47 % of its spawning grounds are concentrated in Selenga. Omul spawns in the Selenga channel within 20–580 km upstream of the lake, and in some years it crosses the border between Russia and Mongolia. Based on long-term (1936–2018) data of the Baikal omul spawning migration in the Selenga River, the relationship between the average migration distance of the spawning herd core and the water discharge at the beginning of the spawning migration (September) was analyzed. Statistical analysis has established an approximate threshold for water discharge, which marks the shortening of the spawning path in «high-water» years and a noticeable extension of it upstream in “low-water” years. The role of other cumulative factors affecting the spawning distance of omul is discussed. Under conditions of a long subglacial period, omul eggs are successfully incubated in large areas for five to six months (November–April). Stability of habitat characteristics in such a shelter is ensured by a significant decrease in flow velocity and temperature, as well as increased water transparency and a relatively favorable oxygen regime. Ice cover formation can also be attributed to protective factors: it reliably shelters eggs from external atmospheric impact: average ice thickness on the river during the study period was 0,5 m (0,1–1,5 m, maximum by spring it often reaches 2 m near the shores). Hydraulic construction in the upper Selenga Watershed in Mongolia could have a significant negative impact on the spawning grounds of the Baikal omul, reducing the survival of its eggs during the winter months. Such impacts, combined with global warming and other anthropogenic disturbances, may even lead to the extinction of this cold-loving endemic of the Selenga Basin, which will undoubtedly affect the entire lake ecosystem.

Publisher

Irkutsk State University

Subject

General Earth and Planetary Sciences,Water Science and Technology,Geography, Planning and Development

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