Freshwater fish - species, habits, habitat

The water area of ​​our planet is about 20 000different kinds of fish. Approximately one-tenth of them refer to commercial fisheries. In addition to food, commercial fish provide us with medicines, industrial raw materials, technical fats, fertilizers, pet food. Fish fishes are divided into freshwater, through-water and marine.

Freshwater fish, whose share in the world catch is about 11%, lives in rivers, lakes and ponds. The largest commercial value is of catfish, carp and percid fish.

The largest fish that live in rivers areAmur kaluga (representative of the sturgeon family), whose weight can reach 1000 kg, and length 5 m, Chinese psephurus (length up to 7 m), European catfish, growing to 5 m in length and over 300 kg in weight, South American arapaim (200 kg of weight , more than 4.5 m in length). But such giants are rare. Most of the freshwater fish that inhabit the domestic water bodies are of average size.

Freshwater fish for commercial purposes partiallyis bred in special artificial ponds - for example, trout, carp, tilapia, cupid, carp. Among the living in rivers and lakes, the most important for catching pike, catfish, carp, crucian carp, bream, perch, roach.

In natural waters, freshwater fish livemostly near the coast, where there is plenty of food and convenient places for spawning. In the summer in shallow water you can always see flocks of fry. The nearest zone is inhabited by fish, not too demanding for water quality, i.e., its purity and oxygen content. This is a pike, crucian, tench, roach. A little further live perch, bream, ide. Catfish, pike perch and salmon choose the most remote and clean places.

Such species of river fish as trout, char, pinwormare found in brooks. In small lakes there are mainly pike, roach, ruff and loach. Large lakes in terms of the number of species are not inferior to sea water. The number of fish species there exceeds several dozen.

The oxygen content in water is the most important factor,It affects the diversity of its inhabitants. In poorly oxygenated water bodies, only the most unpretentious fish are found, since in summer heat and in severe cold many of their species die from suffocation. Lines and carp can exist in oxygen-poor small ponds, which are frozen through in winter. Ruffs tolerate oxygen hunger well, but require clean running water.

The most demanding for high oxygen content are salmon, pike perch, and sturgeon.

Freshwater fish also responds totemperature fluctuations. Some of its species are unable to exist at a temperature below a certain one. Thus, for the fish of the carp family this figure is + 10 ° C. There are fish that do not tolerate high temperatures (whitefish, burbot, palia). In the heat, they hide under the rocks and crawl out only with the onset of cold weather. Other fish can perfectly exist in cold water and survive even in freezing pools. In the freezing winter, certain fish species can fall into an anabiotic state.

Freshwater fish, in addition, is sensitive tosunlight. There are also lovers of lighted and dark ponds. Lamprey prefers darkness, and roach, for example, gathers in sunny, well-lit places. Fry of salmon from bright light is taken into the stones.

Experienced fishermen can determine what kind of fish flashed in the water depth, not only in appearance, but even in a characteristic burst, because each of them moves in its own way.

Fishing in our country is a favorite nationala kind of recreation, which includes elements of the competition, sports excitement, communication, adrenaline rush, fresh air and the practical side of the case in the form of a legitimate catch. Nowadays, there is a practice of breeding fish in special ponds with the subsequent sale of licenses to visit and catch fish in them.