The Danube bleak (Alburnus chalcoides) is a marine fish of the carp family. The Azov-Black Sea Alburnus mento, the Caspian Alburnus chalcoides and the Aral Alburnus chalcoides aralensis are known. Passerine fish. Winters in rivers. Spawns in spring, April-May. Matures in 3-4 years. Eggs are sticky, laid on stony and sandy bottoms. Fecundity is 2-26 thousand eggs. Feeds on zooplankton, aerial insects and young fish. Valuable commercial fish.

Fish with an elongated and laterally compressed body, up to 40 cm long and weighing about 300 g. The mouth is terminal. The lateral line consists of 56-74 scales. Life expectancy is up to 12 years. Different taxonomists distinguish up to 13 subspecies. The body is markedly elongated, the scales are relatively flat (Alburnus alburnus has 46-50 scales on the lateral line, Danube bleak 63-70 scales, and in the vertical row 14-16 scales, Alburnus alburnus 12-13 scales); the anal fin is more posterior than the dorsal fin. The lower jaw is thickened at the tip and protrudes distinctly in front of the upper jaw. Head and back dark with bluish tinge; sides and belly silvery white; all fins greyish, transparent, dorsal and caudal with blackish border; eyes silver with black spot in upper half.

It inhabits the Black, Marmara, Azov, Caspian and Aral seas. The lifestyle of this fish is very poorly known.