Fishes are amazing inhabitants of the water world. This is one of the most numerous and diverse groups of animals. Distinctive features of the structure, classification of fish and the signs underlying it will be considered in our article.
Overclass Pisces: General Description
No wonder self-confident people are compared precisely with these animals. They say about them: "Feels like a fish in water." Indeed, fish possess structural features that enable them to master this habitat. These include a streamlined body shape, the presence of fins and scales, mucus-rich skin and gill breathing.
Classification Basics
These aquatic animals can be grouped according to various criteria. First of all, the classification of fish by structural features is considered. Depending on this, the class of Cartilaginous and Bone is distinguished. Representatives of the latter have more progressive structural features and numbers. Therefore, within the framework of this systematic unit, a number of detachments are still distinguished.
According to the scope of use, decorative and commercial fish are distinguished. The first person bred in aquariums and ponds as a decorative decoration. These are scalars, catfish, neons, guppies, barbs and many others. A person breeds commercial fish for consumption in food. For a long time, their meat and caviar have been a favorite treat, and fat is a valuable medicine.
There is an ecological classification of fish. It takes into account their living conditions. It can be different types of water bodies: fresh, oceanic or marine.
Catch a big fish and ...
The classification of commercial fish also takes into account size. The method of capture and subsequent storage of raw materials depends on this feature. By weight and size, small, medium and large fish are distinguished. Each of these groups has its own valuable qualities. For example, sprats have excellent taste and are widely used in the food industry, despite their very small size.
For commercial fish, gastronomic properties are of particular importance. Therefore, they are distinguished by the amount of fat. For example, cod, saffron cod and hake this figure does not exceed 4%. Such species are considered lean or lean. Sprat, mackerel, herring, saury, sturgeon and stellate sturgeon are considered the highest indicator for this trait. Their fat content significantly exceeds 8%.
In commodity science, the concepts of “species” and “family” are used. Fish, fish classification are determined in trading practice most often on the basis of external signs. For example, the Seldevy family unites representatives in which the body is compressed laterally, and the scales freely fall off. Such fish lack a lateral line. They have a single dorsal fin, while the caudal fin has a characteristic notch. This family includes herring, sprats, kilka, sprats.
Anatomical classification of fish: table
It is generally accepted that when dividing fish into classes, only structural features of the skeleton are taken into account. But it is not so. The basics of anatomical classification are given in the table.
| Signs for comparison | Class Cartilaginous fish | Bone fish class |
| Skeleton structure | Fully formed by cartilage | The skeleton includes bone tissue |
| Presence of gill covers | None, gill slots open outward with independent openings | Present, protect the gills and participate in respiratory movements |
| Swimming bubble | Is absent | Is available |
| Type of fertilization and development | Inner, direct | Outdoor, indirect |
| Features of the selection | The ducts of the digestive, reproductive and excretory systems secrete into the cloaca | There is no cesspool, each organ system opens with its own hole |
Habitat
Habitat classification of fish also defines several groups. The first includes marine inhabitants. This is flounder, herring, halibut, mackerel, cod. Fresh fish are silver carp, sterlet, carp, burbot, crucian carp. They spend their entire lives in the same habitat, where their spawning takes place. 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 through passage
Classification of fish by habitat and lifestyle includes another group called Passers. It includes representatives of the superclass living in the seas, but going to spawn in fresh water. These are sturgeon and salmon fish. Such migratory fish are also called anadromous. But eels during spawning travel in the opposite direction - from rivers to seas. These are typical representatives of catadromous fish.
Pursuing such a difficult path, representatives of the walkers lose a lot of strength. They have to swim against the tide, overcome rapids, waterfalls. All this time they do not eat, but spend their own supply of fat and nutrients. Therefore, many migratory fish come to the breeding place, spawn and die. Already young individuals return to their permanent habitat. It remains a mystery to how fish find their way home. Others are able to spawn several times during their lives. During spawning, external metamorphoses occur with many fish. For example, humpback salmon grows on the back, the jaws bend.
So, the classification of fish is based on several features. These include features of the skeleton and internal structure, size, fat content, habitat, lifestyle, scope of use.