Description and characteristics
The bleak (Alburnus alburnus) is a small, elongated fish with shiny, silvery scales that detach easily. It has a laterally compressed body and a well-marked lateral line. Colouring is silvery with a grey-blue back.
Habitat and distribution
It inhabits the freshwater and brackish waters of the Danube Delta — lakes, branches and canals, living in large schools near the surface in calm waters.
Diet and behaviour
It feeds on plankton, insects, larvae and small invertebrates. As a schooling species it is very active and represents important prey for predatory fish.
Reproduction
Spawning occurs in spring and summer, with females laying numerous eggs on vegetation and bottoms. The fry grow quickly.
Economic and ecological importance
The bleak has an ecological role as a prey species and biological indicator. Locally, it is used as bait or eaten.
Threats and conservation
It is numerous and adaptable, but can be affected by water pollution. It forms large stocks in suitable waters.
Fishing and legal minimum size
The bleak is caught with a rod and small nets. In the table of minimum legal sizes, the bleak (Alburnus alburnus) has a minimum legal size of 12 cm.
Conclusion
The bleak is a numerous schooling cyprinid, essential for the food webs of the Danube Delta.