Expedition on the R/V “G.Yu. Vereshchagin” on May 20-26, 2024

On May 20-26, 2024, on board the R/V “G.Yu. Vereshchagin” an expedition to study the state of the Baikal omul population in the Selenga shallow water zone was conducted within the State Assignments No. 0279-2022-0004 “Assessment of ecological and economic aspects of the impact on Lake Baikal from ongoing and planned anthropogenic factors in the Baikal natural area, rational nature management, water and bioresource potential of Lake Baikal” (led by M.M. Makarov) and No. 0279 2021-0005 “Study of transformations of the state of water bodies and watercourses of Eastern Siberia in seasonal and long-term aspects in the context of climate change, geological environment and anthropogenic loads” (led by Fedotov A.P.).

The purpose of this work is to study the population dynamics of the Baikal omul in the Selenga shallow water zone using the trawl-acoustic method, to estimate the abundance and sex-age structure of the feeding stock.

The hydroacoustic survey was carried out along a standard grid of transects with a total length of more than 350 km. The Echo-Baikal hydroacoustic complex developed at LIN SB RAS was used for the survey. To verify the acoustic data, scientific trawls were conducted using a multi-depth pelagic trawl with fish sampling for biological analysis. A total of five trawls were conducted in different parts of the Selenga shallow water zone at depths ranging from 100 to 250 m.

Preliminary analysis showed the presence of a large number of juvenile fish both in trawl catches and according to hydroacoustic survey data, indicating a steady increase in the omul stock. Compared to 2023, there is an increase in the migration activity of the accumulations and their location on the bed of the bottom slope. It should be noted that at the time of the survey, accumulations of omul were recorded at depths of 100-350 m, with no omul observed above the 100 m isobath. The spatial structure of the accumulations was characterized by a strong heterogeneity, ranging from conditionally “frequently occurring accumulations” to areas with a complete lack of accumulations.

Hydro-acoustic studies of the omul in the open Baikal will be continued during the next cruise of the R/V “G.Yu. Vereshchagin”, which will take place from 29 May to 12 June 2024.