Abundance Dynamics of Broad Whitefish (Coregonus Nasus (Pallas, 1776)) Generations Inhabiting the Lower Reaches of the Ob River in the Period of 1981–2023

This paper estimates the abundance of broad whitefish generations in the lower reaches of the Ob River. Data on the numbers of larvae running down from spawning grounds collected in the main spawning rivers in 1981–2023 make it possible to draw conclusions on the current demographic situation in the broad whitefish population inhabiting the lower reaches of the Ob River, on the impact of anthropogenic factors, and on the water content in the Ob River floodplain with respect to broad whitefish reproduction. In the 1980–1990s, the Severnaya Sosva River was of the greatest significance for broad whitefish reproduction. Since 2010, the contribution of more northern rivers, Voykar and Sob, to the abundance of broad whitefish generations has increased. The significance of the Severnaya Sosva River decreased due to climate warming in the region and the growing extraction of potential breeding stock by the fishery industry, including extraction for fish-farming purposes. The reproduction of the broad whitefish population depends insignificantly on the water content in the Lower Ob floodplain. To restore the broad whitefish population, the reproductive guild protection system should be significantly modified, and a protected area must be designated in the Khulga River basin. Artificial broad whitefish reproduction is not required.