Рыбы являются удивительными обитателями водного of the world. This is one of the largest and most diverse groups of animals. The distinctive features of the structure, the classification of fish and the signs underlying it will be discussed in our article.
No wonder self-confident people are compared withthese animals. They are said to: "Feels like a fish in water." And indeed, the fish have the features of the structure, which allowed them to master this habitat. These include a streamlined body shape, the presence of fins and scales, skin rich in mucus and gill breathing.
These aquatic animals can be grouped bydifferent signs. First of all, we consider the classification of fish on the features of the structure. Depending on this, the class Cartilaginous and Bone are distinguished. Representatives of the latter have more progressive structural features and numbers. Therefore, within the bounds of this systematic unit, a number of detachments are still distinguished.
According to the scope of use there are decorative andcommercial fish. The first person breeds in aquariums and ponds as a decorative ornament. These are the angelfish, catfish, neons, guppies, barbs and many others. Commercial fish man breeds for consumption in food. Long since their meat and caviar are a favorite delicacy, and fat is a valuable medicine.
There is also an ecological classification of fish. It takes into account the conditions of their habitat. It can be different types of water bodies: fresh, oceanic or marine.
The classification of commercial fish also takes into accountthe size. From this feature depends on the method of catching and subsequent storage of raw materials. By weight and size distinguish small, medium and large fish. Each of these groups has its own valuable qualities. For example, sprats have excellent taste and are widely used in the food industry, despite the very small size.
For commercial fish gastronomic propertieshave a special meaning. Therefore, they are distinguished by the amount of fat. For example, in cod, navaga and hake, this indicator does not exceed 4%. Such species are considered lean, or skinny. Sprat, mackerel, herring, saury, sturgeon and stellate sturgeon are considered to be the highest in this characteristic. Their indicator of fat content significantly exceeds the mark of 8%.
In commodity science use the concept of "species" and"families". Fish, classification of fish are determined in trade practice, most often on the basis of external signs. For example, the Herring family unites representatives whose body is compressed from the sides, and the scales fall off freely. Such fish are devoid of lateral line. They have a single dorsal fin, and the caudal fin has a characteristic notch. Herring, sprat, sprat, and sprat belong to this family.
It is believed that when dividing fish into classes, only the features of the skeleton structure are taken into account. But it is not so. The basics of anatomical classification are shown in the table.
| Signs to compare | Class Cartilaginous fishes | Bone fish class |
| Structure of the skeleton | Fully formed by cartilage tissue | The skeleton includes bone |
| The presence of gill covers | None, gill slits open outward with separate openings | Present, protect the gills and participate in respiratory movements |
| Swimming bubble | Absent | There is |
| Type of fertilization and development | Internal, direct | Outer, indirect |
| Selection features | The ducts of the digestive, reproductive and excretory systems are excreted in the cloaca | There is no cloaca, each organ system opens with its own opening. |
Fish classification by habitat is alsodefines several groups. The first is marine inhabitants. This is flounder, herring, halibut, mackerel, cod. Freshwater fish are silver carp, sterlet, carp, burbot, crucian carp. They spend their entire lives in the same habitat, where they spawn. The vital activity of these ecological groups depends on the salinity of the water. So, if marine fish are transferred to fresh water, they will quickly die.
Fish classification by habitat and imageLife includes another group called Passing. It includes representatives of the superclass, living in the seas, but going to freshwater reservoirs for spawning. These are sturgeon and salmon fishes. Such migratory fish are also called anadromous. But eels during spawning travel in the opposite direction - from rivers to the sea. These are typical representatives of catadromous fish.
Doing such a difficult journey, representativescheckpoints are losing a lot of power. They have to swim against the current, overcome rapids, waterfalls. All this time they do not eat, and spend their own fat and nutrients. Therefore, many migratory fish swim to the breeding site, spawn and die. Already young individuals return to their permanent habitat. It still remains a mystery how the fish find their way home. Others are able to spawn several times during life. During spawning, external metamorphosis occurs with many fish. For example, a pink salmon has a hump on its back, its jaws are bent.
So, the classification of fish is based on several signs. These include the features of the skeleton and the internal structure, size, fat content, habitat, lifestyle, scope of use.
