Russian sturgeon (Acipenser gueldenstaedtii) is a passable fish of the sturgeon family. Length up to 2.5 m, weight up to 200 kg. It inhabits the basins of the Caspian, Black and Azov Seas. The snout is short and blunt. The antennae are located closer to the end of the snout. The lower lip is interrupted. Large and small stellate plates are scattered between rows of beetles. In a number of water bodies it forms residential forms. Feeds on mollusks and fish. It has an important commercial value.

Gill membranes grafted to intergillar interval, fold under it absent. The snout is short, rounded. The lower lip is discontinuous. Antennal antennae without fringe, not reaching the mouth; in bent forward they reach the end of the snout. Body between rows of beetles usually covered with rows of stellate plates. Number of rays in the first dorsal fin 25-51, in the anal fin 19-36, dorsal beetles 8-18, lateral beetles 23-50, pelvic beetles 6-13; gill stamens 9-31. Dorsum gray-brown, sides gray-yellow, belly light.

Life expectancy up to 46 years. Average body mass is 15-25 kg. Maximum body length is 236 cm and mass is 115 kg.

In the Caspian Sea it makes spawning and feeding migrations: in spring they are directed to the north and to the coastal strip, and in fall - to the south and to deeper parts of the sea. The main sturgeon river is the Volga. In the Volga above the delta, sturgeon mass migration occurs in July (in the lower reaches of the Volga, the peak sometimes falls in June), in the Ural River there are two peaks: in spring (April-May) and in late summer-autumn, and in the Kura River it occurs throughout the year with a peak in March-April. Fish that come in spring and partly in summer spawn in the year of entering the river; sturgeons that entered the river in summer and fall overwinter there and spawn in early spring the following year. After marking their eggs, sturgeons roll into the sea, where they fatten up until the next spawning. In the Azov basin, sturgeon spawning migrations to the Don River have been preserved.

Spawning occurs in the lower reaches of regulated rivers (Volga, Terek, Kura, Sefidruda) and the Urals. Breeding occurs at 9-15 °C. Effective spawning is possible only in full-water years. Males become sexually mature at the age of 8-13 years; females - 8-20 years. Most females spawn for the second time at the age of 17-23 years (80%), and for the third time at the age of 21-24 years (87%). The average age of females at the first - fourth spawning is 15, 20, 22 and 24.5 years, and of males - 12.5, 16.2 and 18.8 years. Adhesive eggs are laid on the substrate, can develop and free form between stones. The length of larvae is 11-12.5 mm. The period of yolk feeding is 1-10 days, mixed feeding - from the 10th to the 15th day. At present, juvenile sturgeon almost never stay in the river; in the Volga, intensive rolling occurs in late June - early July, in the Kura - in July. The size of skate fry in the Volga is 21-50 mm, in the Kura - 25-85 mm.

In the Caspian Sea, seedlings feed on mysids, gammarids, and amphipods. Fish appear in the diet when sturgeons reach a length of 26 cm. Adults feed on crustaceans, mollusks and fish (sprat, herring, atherium, shemaya, mullet). The diet of sturgeons aged 2-3 years in Taganrog Bay is based on gobies (57%) and crustaceans (35%). In the sea, sturgeons feed mainly on mollusks (Abra, Carbulemia, Lentiphium, Cerastoderma) - 75-97 % and worms (up to 20 %). The main food competitors in the Caspian and Azov-Black Sea basins are gobies, starred sturgeon and flounder. The juvenile Russian sturgeon is hunted by predatory fish. The laid eggs are eaten by gouster, white-eye grouper, gudgeon and other benthophagous fish. The larvae are hunted by herring and chekhon, while small juveniles are hunted by bullheads, catfish and pikeperch. In nature, sturgeon forms interbreeding with beluga, Sevruga, spike, and sterlet. In the form of hybrids, it can serve as a basis for commercial sturgeon farming.