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
Fishing is one of the oldest forms of economic activity of people. Fish for a man — a very valuable source of food (animal proteins and fats), which are easier to digest than vegetable.
Industrial fishing is carried out in the seas, oceans, large rivers, lakes. Fish are grown in specially constructed ponds. Basic ocean space, where year-round fishing, is a subtropical and tropical waters of the Atlantic, Pacific and Indian oceans. These areas of the oceans do not freeze. In areas close to the North pole, the water is cooled, and the Arctic ocean has a permanent ice cover.
Anyone caught in the oceans? Oceanic herring (Atlantic, Pacific), herring, sardine iwashi. These herring are distinguished easily detached scales and gregarious way of life.
In Northern waters catching cod, haddock, saffron cod. These trnkobrani (Fig. 127) can be recognized by the barbels on the chin and three unpaired fins on the back. These fish have long and traditionally fished and loved in Russia.
Fig. 127. Representatives trnkobrani: 1 – cod; 2 – burbot
In the ocean catch and other fish, all familiar names: ocean perch, Alaska Pollock, Grenadier, hake, flounder. Fisheries in the oceans is, as a rule,in places close to the coast, at a depth of 400-500 m. This region of the shelf — coastal ocean shallows at the threshold of transition to greater depths. Here collects a lot of fish. To fish from such depths is designed and gear. In the oceans and seas, fish are caught using trawls, fyke-nets. In our country fish catch in inland seas. For example, small Caspian sprat catches in the Black, Continue reading
Sea of the Pacific ocean. The waters of the sea of Okhotsk. The strategic importance of the Black sea. Closed in the shores of a large natural pond. The largest lake in Europe. The largest river of the East European plain. Caspian lake is the largest in the world.
Key features of the Black sea: the salinity of the water, the annual course of temperature, depth. The concept of the geological history of the Black sea, the vertical temperature distribution in the Black sea. The proliferation of different departments of tertiary sediments on the coasts.
Geographical position and features of the structure of the Black world. Average monthly temperatures in the Black sea at the surface. Two layers of water with different physical properties, their distinctive features. Causes of hydrogen sulfide in the depths of the sea.
The main geographical features of the Caspian sea: hydrological characteristics, hydrochemical conditions, seismic situation. Economic use of marine resources. The need for urgent measures to improve the environmental situation.
Geographical and Maritime characteristics of the Atlantic ocean, its role in modern international cargo and passenger transportation. The influence of Atlantic water on the flora and fauna of the Northern seas. Characteristics of the main Straits of the Atlantic ocean. Continue reading