Reproduction and Genetic Differentiation of Nelma (Stenodus nelma Pallas, 1773) in Large River Basins of Western Siberia

The results of the assessment of the natural reproduction and population structure of nelma in the Ob’ and Taz basins are presented. Based on data on the abundance of fish larvae migrating from spawning grounds and the dynamics of catches, a conclusion was made about the constant decline in the abundance of the species over the course of 60 years. Long-term analysis of the size–age variability of nelma in the Severnaya Sos’va River indicates a persistent rejuvenation of the spawning stock at the present stage and the absence of rematuring specimens in it. An analysis of the genetic differentiation of nelma populations in the Ob’ and Taz rivers was conducted. No genetic differences were found between the two basins, which indicates the genetic closeness of nelma populations within Western Siberia. The possibility of restoring the nelma population through artificial reproduction has been assessed.