Sterlet is a valuable commercial fish. Along with other sturgeon species it belongs to the family Acipenseridae. It lives in the basins of the Black Sea, the Sea of Azov, the Caspian Sea and the Baltic Sea. It may be found in such big rivers as the Volga and its tributaries, the Don, the Ob River and The Irtysh River. Sterlet lives a rather secretive life. In the riverbeds, it chooses deep areas with sandy bottom without silt. It prefers river segments with strong currents and cool water. Sterlet feeds on small bottom invertebrates: insect larvae, mollusks, crustaceans. It eats roe of other fish species. Sterlet moves to the surface to pick insects fallen into water. It is distinguished from other Acipenseridae by its small size, narrow oblong nose and long fringed barbels reaching its mouth. Its lower lip is interrupted in its center. Its spindle-shaped body, like that of other sturgeon species, is covered with bony plates (scutes) instead of scales, forming five lateral rows. Its body coloration varies from light yellow to grayish tawny. An average commercial fish is about 40 to 60 cm long and weights from 500 g to 2 kg. Large specimens may reach a length of 120 cm and a weight exceeding 10 kg.