Author: (Güldenstädt, 1772)
FBname: Danube bleak
Comments: Inhabit lower reaches of rives, coastal lakes, estuaries, and brackish areas of sea.  Occur close to surface and tolerate salinities up to 14 ppt.  Adults predominantly prey on planktonic crustaceans, terrestrial insects and small fish while larvae and young juveniles feed on zooplankton, algae and insect larvae.  Spawn in small rivers or streams with heavy current on gravel bottom.  Landlocked populations found in reservoirs spawn in reservoir tributaries (Ref. 59043).  Eastern populations migrate upstream for spawning (Ref. 13696).  Males assemble and wait at the spawning grounds for ripe females, which arrive later.  Deposit sticky eggs which adhere on pebbles or stones.  Embryonic development lasts 2-3 days, with larvae first staying among gravel for 8-11 days, then actively migrating to shallows and backwaters. Adults migrate back to sea, lakes or estuaries soon after spawning to forage.  Young juvenile undertake downriver migration in autumn of same year or next spring.  Due to dam constructions, almost all long-distance migrating populations lost as they were unable to reach spawning sites.  Survive in small water courses and as landlocked populations in some reservoirs.  Populations are expected to decline and to further decline due to expanding hydroelectric development and strong ecological impacts on Caspian sea  (Ref. 59043).