Blicca bjoerkna is a freshwater fish of the carp family. Length up to 35 cm, weight up to 1.3 kg, usually 100-200 g. It lives in the water bodies of Europe and in the basins of the Northern, Baltic, Caspian, Black and Azov Seas. It matures at the age of 3-4 years. In southern reservoirs, it matures one year earlier and in northern reservoirs, one year later. It spawns in portions, stretching from May to July. Fertility is rather high, up to 125 thousand and more eggs. The eggs are laid on the bottom vegetation. A gregarious fish, very close to bream. In spring and fall, it forms numerous flocks or "dense" aggregations, hence the name of the fish. Silvery, strongly flattened at the sides of the body resembles a young bream. It differs from bream only in the number and location of pharyngeal teeth, which are not five on each side, but seven, and even in two rows. Blicca bjoerkna feeds on benthic zooplankton, chironomid larvae, mollusks, and small bristleworms. Its fishery value is low.
The body of blicca bjoerkna is strongly flattened, and its height is not less than one third of its entire length; its nose is blunt, its eyes large, silvery; its back is bluish-gray, the sides of the body bluish-silvery; the unpaired fins are gray, and the paired at the base are red or reddish, dark gray at the top. However, this fish, depending on age, time of year, and local conditions, presents significant variations.
Blicca bjoerkna is a sluggish, lazy fish and, like the bream, likes quiet, deep, rather warm water, with muddy or clay bottom, why it is very often found together with the bream. It lives in one place for a long time and most readily keeps at the very shores, especially in the wind, as waves, eroding the shores, and in shallow places the very bottom, find various worms and larvae. In spring and fall blicca bjoerkna is found in extremely dense flocks. It rarely makes very long journeys and almost does not reach, for example, the middle course of the Volga, where it already lives its own, local blicca bjoerkna. In general, the main mass of these fish concentrates in the lower reaches of rivers, in the sea, and, like very many others, they make periodic movements: they go up in spring to spawn, and in autumn to overwinter. Entering the fall for wintering, they lie in the holes under the rifts in such large masses that in the lower reaches of the Volga it happens in one ton pull up to 30 thousand pieces. The bream's diet is almost identical to that of other bream species: it feeds exclusively on the mud and small mollusks, crustaceans and worms enclosed in it, mostly chub, but it also destroys the eggs of other fish, especially the roe of the redfin.
Fish spawning begins very late, at the end of bream spawning - in late May or early June, in the south somewhat earlier. At this time, its scales change color, and the paired fins become brighter red; males also develop small granular tubercles on the gill covers and at the edges of the scales, which then disappear again. Usually small blicca bjoerkna spawns earlier and large blicca bjoerkna later. In the Gulf of Finland, fishermen even distinguish two breeds of gusters: one breed, they say, is smaller, lighter, spawns earlier and is called Troitskaya (according to the spawning time), and the other breed is much larger (up to 3 pounds), darker in color, spawns later and is called Ivanovskaya. By place of spawning blicca bjoerkna chooses grassy and shallow bays and spawns extremely noisily, like the bream, but incomparably more humble than him: at this time, sometimes it even happens to catch her hands. She usually spawns from dusk to ten in the morning, and every age finishes the game at 3-4 in the night, but if the cold weather interferes, then one day. A medium-sized female has more than 100 thousand eggs.
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