Distribution and migration cycle of nelma Stenodus leucichthys nelma (Pallas, 1773)

Abstract

The article considers the natural habitat and migrations of nelma Stenodus leucichthys nelma (Pallas, 1773) on the basis of literary sources. This fish is a subspecies of white salmon. It belongs to the genus of nelma of the whitefish family and is of great interest for researchers, as nelma is one of the most valuable commercial objects. According to the result of analysis and data systematization, nelma is found to migrate to all major rivers flowing into the Arctic Ocean. In the rivers and lakes under consideration it is represented by the semi-anadromous species, as well as non-migratory river and lake species. The hydrological description of the reservoir has a huge influence on nelma’s migrations and biotopes. Data on the anthropogenic factor influence on the migration of this subspecies are also given. It has been stated that the construction of hydroelectric power stations, building the reservoirs and regulation of river flows negatively affect this biological complex phenomenon. After blocking some large rivers by hydroelectric dams many populations of the Ob and Yenisei nelma were deprived of their natural habitat, the duration and extent of migrations were reduced, and non-migratory (residential) stocks developed in the upper reaches of the Ob, the Yenisei and the reservoirs. Due to the human intervention in the natural processes of fish development and reproduction, the stocks of valuable commercial species have been greatly reduced. Thus, this factor has brought in the significant changes in the life cycle of nelma. In general, it can be inferred that nelma migrations in individual water bodies have not been studied enough and require detailed consideration in order to protect and preserve this rare subspecies of the whitefish family.