Methodological aspects of estimating natural mortality coefficients for the baikal omul: a case study of The selenga population

Abstract

This scientific article presents a critical analysis of methods for estimating the instantaneous natural mortality coefficient (M) of the Baikal omul, Coregonus migratorius (Georgi, 1775), in the context of managing its commercial stock. The von Bertalanffy growth equation was parameterized based on growth and age structure data. A comparative analysis of existing M estimates used in the Total Allowable Catch (TAC) materials for 2017–2025 revealed their significant variability, leading to threefold discrepancies in the calculated population biomass under equal recruitment. An important factor determining the dynamics of cohort abundance and biomass is the extremely high post-spawning mortality (>90%) in the Selenga population. The applicability of theoretical models based on life history invariants for calculating average M values (Jensen, 1996) is justified using the concept of maximum age (Shibaev, 2023). The resulting estimate based on maximum age, M_avg=0.19 yr⁻¹, and the ratio M/K≈1.5 yield more realistic projections consistent with historical fishery data. The reliability criterion for any M estimation method should be its consistency with key population indicators, taking into account the spatial heterogeneity of the stock.