Anadromous Sturgeons (Acipenseridae, Actinopterygii) of the Don River Upstream from the Tsimlyansk Hydroengineering Complex

Abstract

Data based on the results of published, unpublished, and questionable materials concerning the occurrence of anadromous sturgeons after damming of the Don River downstream and upstream of the Tsimlyansk hydroengineering complex are presented. Two peaks of approaches of spawners to the dam in the 1950s and 1980s were recorded. The first peak was related to the wild population that existed in these years; the second peak was a result of mass artificial propagation. At the first stage, the Russian sturgeon (Acipenser gueldenstaedtii Brandt et Ratzeburg, 1833) and the beluga sturgeon (Huso huso (Linnaeus, 1758)) prevailed downstream from the dam; at the second stage, only the Russian sturgeon was recorded. Since 1955, only 21 individuals of anadromous sturgeons have made it through the dam by a fish ladder. During the years 1952-1961, 1145 individuals were transported into the reservoir, including 218 ind. of beluga. Some individuals of beluga were transported later as well. There are data indicating the presence of juvenile beluga individuals that originated from natural spawning in the reservoir before the 1970s. The last known spawners of Russian sturgeon and stellate sturgeon (Acipenser stellatus Pallas, 1771) in the reservoir were recorded in the 1980s or 1990s. Solitary beluga individuals may occur nowadays. It is suggested that the youngest of the noted individuals belong to the generations of the early 1990s. It is concluded that the extremely innumerous landlocked form of the Azov beluga may still exist in the reservoir.

River Damming Impacts on Fish Habitat and Associated Conservation Measures

“…The Volgograd Dam has reduced the area of Russian sturgeon spawning grounds by 80% (Secor et al., 2000), and the limited spawning area led to high spawning densities, resulting in egg mortality rates of up to 60% (Popov, 2017). In the Don River, Russia, dams cut off the main path of Russian sturgeon migrating to their spawning grounds, resulting in a sharp reduction in their spawning areas that are only located downstream of the dam (Boldyrev, 2018). At present, Russian sturgeon with natural reproduction only exists in the undammed Ural River in Russia and Kazakhstan.…”