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. Continue reading
The China red crucian (Carassius)
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Gold, or Chinese, crucian carp (Carassius auratus) found in the wild in Korea, China and Japan. This crucian carp in nature has a Golden hue, especially in shallow, well warmed by the sun waters.
Of all aquarium fish, goldfish have the longest history. Goldfish, a domesticated form of the Golden carp was first bred in China over 1500 years ago, where these, taking advantage of the variability of carp in coloration and in the shape of the body, engaged in the culture of ornamental carp. Goldfish bred in garden ponds and reservoirs in the estates of the nobility and wealthy people. It was the first time goldfish imported in the mid-eighteenth century. Currently widespread many varieties of goldfish.
Main color of body and fins reddish-Golden, the back is darker than the abdomen. Other types of coloring: pale pink, red, white, black, black-blue, yellow, dark bronze, fiery red. The body of a gold fish is elongated, slightly compressed laterally. In ponds goldfish can grow up to 35 cm, but in a normal aquarium its size is much smaller. To distinguish males from females monolist during the spawning season. Then the female has a rounded abdomen, while the males have pectoral fins and the gills there are a white “rash”. Continue reading
Shark is a marine predator, which has animal instincts, and we can’t predict a shark will attack or not.
Bearded shark in camouflage, Indonesia, Indian ocean. However, it is easily recognized by the beard, which frames the head. These outgrowths attach to the shark very funny. Its flattened body is grayish or yellowish brown with large light spots. This allows the shark is easily distinguished from the surrounding sandy seabed and corals. She swims at a small depth , among coral reefs.
The shark has an average size – about 1-1. 5 meters. Although some specimens can reach 3-4 meters, but this happens very rarely. Besides fish, bearded sharks eat invertebrates that live on the bottom.
The degree of hazard to humans: medium.
For man bearded shark is not dangerous, it is important not to anger. But if to dismiss his hands, carrying her by the tail and poking, painful bite is guaranteed.
Bull shark or bull shark
Bull shark, the Pacific ocean. Continue reading