Danube bleak gravel bottoms. The females arrive later and deposit about twenty thousand eggs which stick to stones and gravel. These hatch after two or three days and the larvae stay among the gravel for another ten days before moving to backwaters and shallows where they feed on zooplankton, insect larvae and algae. The juvenile fish migrate down stream in the autumn or the spring of the following year. They may become mature in four to five years. Danube bleak The Danube bleak or Caspian shemaya ("Alburnus chalcoides") is a species of freshwater fish in the family Cyprinidae. It is found in
Common species because common species shape ecosystems, contribute disproportionately to ecosystem functioning, and can show rapid population declines, conservation should look more closely at how the trade-off between species extinctions and the depletion of populations. Common species Common species and uncommon species are designations used in ecology to describe the population status of a species. Commonness is closely related to abundance. Abundance refers to the frequency with which a species is found in controlled samples; in contrast, species are defined as common or uncommon based on their overall presence in the environment. A species may be locally abundant without being common. However,