The breeding of sterlet
One of the most difficult and pressing problems of the modern world is the problem of providing a growing world population with food. At the same time it is closely intertwined with the problem of environmental protection (Grigoriev, Sedova, 2008). Despite a General tendency to the reduction of fish stocks in the seas and oceans are of particular importance in aquaculture, i.e. fish farming, food invertebrates and algae in a controlled environment. Artificial reproduction of fish stocks in natural waters is a complex of measures aimed at the preservation, increase quality and increase fish stocks. These activities include fish farming, fisheries management melioratio, acclimatization of fishes and food organisms, as well as clear regulation of the fisheries.
Sterlet (lat. Acipenser ruthenus ) — fish of the family Acipenseridae. Body length up to 125 cm and weigh up to 16 kg (usually less). Among other sturgeon species is distinguished by the early onset of sexual maturity: males first spawn at the age of 4-5 years, females — 7-8 years. Fertility 4–TIC eggs. Working fecundity of 33 thousand eggs. Spawn in may, usually in beds of the upper reaches of the rivers. Caviar adhesive, is deposited on the stony-pebble ground. It develops about 4-5 days. Adults usually reach a length of 40-60 cm and mass 0.5–2 kg, sometimes there are specimens weighing 6-7 kg and even up to 16 kg. Feeds mainly on benthic invertebrates, willingly eats caviar of fishes. In the fall, in September, is going on deep sections of rivers (ditches), where it spends the winter in an inactive state, not feeding. The regulation of rivers usually improves the conditions of feeding sterlet, but also worsens the conditions of its reproduction. The age limit of sturgeon for 30 years. A valuable commercial fish. Object of pond and lake breeding. The sterlet is very widespread, living in rivers of the Black, Azov, Caspian and Baltic seas. In the late 18th — early 19th century (possibly earlier) through a system of canals starlet penetrate from the basin of the Kama and Northern Dvina. Were carried out in the past in lakes Onega and Ladoga. Is in the large Siberian rivers — Ob, Irtysh and Yenisei, where a separate subspecies — the Siberian sterlet ( Acipenser ruthenus marsiglii ). Further to the East (the Pyasina, Khatanga, Lena, Kolyma) the starlet is missing. The main sterlet river is the Volga with its tributaries, the don, the Ob with the Irtysh. Sturgeon transplanted to many waters: Pechora. The Western Dvina, the Mezen, the Neman river, the Amur, but not everywhere it takes root.
Sturgeon is a typical freshwater fish, but in the Volga basin in a small number of common major and semi-anadromous form (average length of females is 74 cm and weight 2.8 kg), which fatten on the rich pastures North of the Caspian sea and on spawning rises low on the river. This form of sterlet was even a separate species ( Acipenser primigenivus ). Sturgeon are very variable in shape of the snout, many researchers identify it has two forms: dumb and estroril. Dwarf sturgeon has a more rapid growth, it is more tubby and has a greater fecundity compared to ostrorog. Sometimes dumb starlet is seen as a winter form, and Ostromila — like spring. It is moored in the river to the pits, where it accumulates in large numbers in spring, in high water, heads upstream to spawning grounds. Propagated sturgeon in the river and flooded the coastal rocky ridges. The peak of spawning on the Middle Volga in may. On the spawning grounds are usually dominated by males, each of which, apparently, involved in the insemination of eggs of several females. Sexual maturity in the river (Volga) in males sturgeon occurred in 4-5 years, females — at the age 7-9 years. Fecundity varies greatly, which is determined by the size of the females. Volga sterlet lays from 4 to 140 thousand eggs, the Ob — from 6 to 45 thousand, Irtysh — from 6 to 16 thousand. Still not clarified the question of the frequency of spawning sturgeon. Some researchers believe that the sturgeon narastaet each year; others come to the conclusion that it is bred with an interval of 1-2 years.
After spawning, the sturgeon intensively raise. Its food consists of small benthic invertebrates: larvae of chironomids, midges, mayflies, caddisflies, and mollusks. Readily eats it also delayed other fish eggs, including anadromous sturgeons. During the summer mayflies sturgeon rises to the surface, flipped upside down and collects her mouth fallen insects.
This kind of traditional and long-standing object of pond cultivation. In 1971 Moscow was the first to receive offspring from the producers of sterlet reared in cages installed in the reservoir and was later obtained the eggs and fry of the fishes contained in the warm sector with GRES, which opens up great prospects for use of this valuable species in commercial sturgeon farming. (Kozlov, Abramowitz 1991).