The bleak or common bleak ( Alburnus alburnus) is a small freshwater coarse fish of the family Leuciscidae, which includes the minnows, daces and bleaks.
Description
The body of the bleak is elongated and flat. The head is pointed and the relatively small mouth is turned upwards. The anal fin is long and has 18–23 fin rays. The
lateral line is complete. The bleak has a shiny silvery colour, and the
are pointed and colourless. Its maximum length is about 25 cm (10 in).
In Europe, the bleak can easily be confused with many other species. In England, young common bream and Blicca bjoerkna can be confused with young bleak, though the pointed, upward-turned mouth of the bleak is already distinctive at young stages. Young Rutilus rutilus and ruffe have wider bodies and short anal fins.
Occurrence
The bleak occurs in
Europe and Western Asia: north of the
Caucasus,
Pyrenees, and
Alps, and eastward toward the
Volga basin in
northern Iran and north-western
Turkey. It is absent from Iberian and Apennine peninsulas, from the rivers of
Adriatic Sea watershed on the
Balkans and most of British Isles except southeast England. It is locally introduced in
Spain,
Portugal, and
Italy, though.
Ecology
The bleak lives in great schools and feeds upon small
, insects that fall in the water, insect
,
, small
shellfish, and
detritus. It is found in
and
. The bleak prefers open waters and is found in large numbers where an inflow of food from pumping stations or behind weirs occurs.
Spawning
The bleak spawns near the shore in shallow waters. Some are found in deep water. The substrate is not important.
Reproduction
Source:
[Billouttes.eu : Panfish: Common Bleak (Alburnus alburnus)]
The Common Bleak typically reaches sexual maturity at around three years of age. Its spawning period takes place from April to June when the water temperature ranges between 14 and 15 °C (approximately 58 °F).
During this time, a female Common Bleak can lay between 5,000 and 7,000 eggs in multiple batches. These eggs are deposited on submerged vegetation or shallow areas of the water. Males undergo changes during the spawning season, developing nuptial tubercles on their backs and flanks, while their fins take on an orange hue. The incubation period for the eggs lasts about 2 to 3 weeks.
The growth rate of the young fish, known as fry, is relatively slow, and their primary source of nutrition is plankton. It is also possible for hybridization to occur between the Common Bleak and other cyprinid fish species, such as Chub, Roach, Scardinius, or Bream.
Importance
The bleak is an important food source for
predatory fish. It is more sensitive to pollution than other cyprinids, which might explain the decline in north-western Europe.
Uses
Bleak are used as bait for sport-fishing for larger fish. In 1656 in Paris, a Mr. Jaquin extracted from the scales of the common bleak, so-called
essence Orientale[ or "pearl essence",][Johann Rudolf von Wagner, Ferdinand Fischer, and L. Gautier, Traité de chimie industrielle (Treatise on industrial chemistry), 4th ed., (Paris, France: Masson & Co., 1903), vol. 2, pp. 64–65.] (used in making Imitation pearl), which is crystalline guanine.[In 1861, French chemist Charles-Louis Barreswil (1817–1870) found that "pearl essence" was guanine. See: Barreswil (1861) "Sur le blanc d'ablette qui sert à la fabrication des perles fausses" (On the white of ablette that's used in making imitation pearls), Comptes rendus, 53 : 246.]
