Population structure and condition of Siberian sturgeon stock: Acipenser baeri Brandt in the River Basin of the Ob

Abstract

This paper summarises materials from various sources and the author’s research on the biology of the Siberian sturgeon in the Ob basin. The paper evaluates the significance of various parts of this river system for habitation and formation of sturgeon stock. It has been possible to distinguish semi-diadromous sturgeon and four local (indigenous) schools, according to the difference in morphological characteristics and peculiarities of the Ob basin ecology. Semi-diadromous sturgeon spends most of their life in the lower reach of the Ob and in the Gulf of Ob and migrates to spawn to the upper Ob. These spawning migrations cover a distance of 2500 km or more. Spawners from local schools do not make such long spawning migrations. It is noted that at least two isolated schools have been formed higher up the dams of the hydroelectric power stations on the Ob and the Irtysh. Today, the stock of semi-diadromous sturgeon is extremely low, but this school used to be the most abundant. The population of young fish in the middle-Ob school is of high density. But it has an extremely high mortality rate. The Chulym school of Ob sturgeon is in the best condition. Its population increases from the waters of two sturgeon and nelma reserves.