Invasive Species Compendium

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Abstract

The distribution of vimba bream Vimba vimbaVimba (Actinopterygii: Cyprinidae) in the unregulated section of the lower Volga River.

Abstract

This paper presents recent data on the population of the anadromous vimba bream (Vimba vimba vimba), introduced in the Volga basin. After penetration to the downstream section of the Volga River from the Volgograd Reservoir, vimba bream can be found throughout the entire unregulated stretch downstream of the Volga Hydroelectric Station. Observations show that the population size changes naturally during the year owing to its spawning migration. At the same time, a gradual transformation of the seasonal dynamics of the species is observed. As populations spread further downstream, the migrations of spawners downstream of the dam become longer, and the population density decreases. Also a seasonal redistribution takes place, with reduced migration observed in autumn and increased migration during spring. Meanwhile, the growth rate in the downstream section of the Volga River is comparable to the growth rate of populations in the Volgograd and Tsimlyansk reservoirs. Spawning occurs on in-channel spawning grounds. Yearlings are observed over a distance of 100 km downstream of the dam. In addition to Vimba bream, single specimens of Caspian bream (V. v. persa) are also recorded.