Nelma (Stenodus leucichthys nelma) is a Siberian subspecies of the genus Nelma in the whitefish family. It reaches 130-150 cm in length and weighs up to 28, sometimes 40 kg. It is characterized by a large mouth, small teeth on the jaws. Gill stamens are 20-21. Inhabits the seas of the Arctic Ocean. In some rivers and lakes forms residential forms. Semi-passable fish. It enters rivers for spawning, ascending them for considerable distances, sometimes 3900 km (Ob). Sexual maturity comes late, at the age of 7-18 years. It spawns in late September-October. Spawning is non-annual, with an interval of 3-4 years. Lays eggs on rocky-pebble soils. Fecundity is 125-325 thousand eggs. It feeds mainly on fish. Valuable commercial fish. In some rivers irrational fishing has led to undermining of its stocks.

Semi-passable or freshwater fish. Length - up to 1.3 m, weight - up to 50 kg. Spawning in the fall. Fecundity - 125-420 thousand eggs. Eggs develop between stones during the whole winter. Predator since the first year of life. It feeds on smelt, ripple, juvenile whitefish, as well as juvenile carp and perch fish. Valuable commercial fish; a breeding target. Local forms are known. Nelma is a large fish. It reaches 30 and even 40 kg; the average weight in different reservoirs varies from 5 to 12 kg. Nelma spawns in the second half of September and in October at water temperatures from 3 to 8°, mainly in fast places with sandy-pebble soil. The life cycle of this fish is up to 16 years in the Irtysh, Pechora and Ob, and up to 22 years in the Yenisei, Lena and Anadyr.

It is most abundant in large rivers - the Ob, Irtysh, Yenisei, Lena and Indigirka. Recently, it has been caught intensively by amateur fishermen using various trollers in summer and fall. Nelma numbers are declining everywhere due to mass catching and deterioration of reproduction conditions.