The bastard sturgeon (Acipenser nudiventris) is a passage fish of the sturgeon family. It is the most valuable commercial fish.

The appearance is characteristic of sturgeons. The lower lip is continuous, not interrupted in the middle. The antennae are fringed. The first dorsal carapace is large. Of the five rows of carapaces, the dorsal row consists of 11-17 beetles, the lateral rows 52-72 beetles and the ventral rows 12-17 beetles. The first gill arch has 21-40 (24-36) gill stamens. Body length up to 220 cm, weight up to 80 kg. Passable. It enters rivers to spawn. Eggs are laid on gravel banks. In April-May at a water temperature of 10-15°C. Forms spring and winter forms. Males mature at 6-9 years, females at 12-14 years. Spawns in March-May. Fecundity is from 200 to 1290 thousand eggs.

Occurs in the basins of the Caspian, Aral, Black and Azov Seas; in the Black Sea, especially the Azov Sea, it has almost disappeared. In the Aral Sea it disappeared after the beginning of its drying up and the cessation of the outflow of the Amu Darya and Syr Darya. It is a semi-transient fish because it winters in rivers. In addition, in the Aral Sea it was represented only by the winter race. In the Caspian Sea, it inhabits mainly the southern part, from where it enters the Kura River to spawn; in the Iranian part, it enters the Sefidrud River.

It lives up to 30 years and more, reaching a length of 214 cm and a weight of 80 kg. In the Aral Sea, the majority of catches were 12-21 years old, with sexual maturity occurring at 12-14 years. In the Kura, catches consisted of fish from 6 to 23 years old; the majority of males were 9-16 years old and females 14-19 years old. The average commercial weight was about 12-16 kg in the Aral and about 20 kg in the Kura. Fecundity of Aral sturgeon is 216-388 thousand eggs, Caspian sturgeon - 280-1290 thousand eggs (average - 593 thousand eggs). In the Aral Sea the main food was molluscs, in the Caspian Sea - fish and molluscs. In the Balkhash lake there is only winter race.

In the wild, bastard sturgeon forms interbreeds with Huso huso, with Acipenser stellatus and with Acipenser gueldenstaedtii.