IUCN: EN; RDBUkr: Вразливі
Value of species
Published morphological data suggest that two species of shemayas were possibly present in the lower Danube until about 1940. One of them (Alburnus danubicus) is now Extinct.
This fish occurs in the Black Sea basin in the lower and middle course of the Danube, lower Dniepr and South Bug, and coastal lakes. It is very rare in the Danube.
Population size and trends are unknown.
This species occupies the lower and middle parts of rivers, estuaries, coastal lakes and adjacent areas of seas where salinity is lowered by large inflow of freshwater. It tolerates salinities up to 12%. Spawning occurs in riffles with heavy current on gravel bottom, today mostly below dams.
The species usually has semi-anadromous populations. The Danube has only a residual population left. It spawns for the first time at 2–4 years, females one year later than males. It starts entering rivers in autumn and moves upstream during winter and/or spring; spawning occurs in May–July at 18–26°C. Eggs are sticky and adhere to pebbles or stones. Adults return to the sea, lakes or estuaries soon after spawning to forage. Young juveniles move downstream in the autumn of the same year or the following spring. Larvae and young juveniles feed on zooplankton, algae and insect larvae, while adults mainly feed on planktonic crustaceans, terrestrial insects, and small fish. This species regularly hybridizes with Squalius cephalus.