Fish are amazing inhabitants of the water world. This is one of the most numerous and diverse groups of animals. The distinctive features of the structure, the classification of fish and the features underlying it will be discussed in our article.
Superclass Pisces: general characteristics
It is not for nothing that self-confident people are compared with these animals. They say about them: "Feels like a fish in water." Indeed, fish have structural features that have allowed them to master this habitat. These include a streamlined body, fins and scales, mucus-rich skin, and gill breathing.
Classification basics
These aquatic animals can be grouped according to different characteristics. First of all, the classification of fish according to structural features is considered. Depending on this, the class Cartilaginous and Bone are distinguished. Representatives of the latter have more progressive structural features and numbers. Therefore, within this systematic unit, a number of detachments are still distinguished.
According to the scope of use, ornamental and commercial fish are distinguished. Firstman breeds in aquariums and ponds as a decorative ornament. These are angelfish, catfish, neon, guppies, barbs and many others. Commercial fish are bred for human consumption. Their meat and caviar have long been a favorite delicacy, and their fat has been a valuable medicine.
There is also an ecological classification of fish. It takes into account their living conditions. These can be different types of water bodies: fresh, oceanic or marine.
Catch a big fish and …
Classification of commercial fish also takes into account the size. The method of catching 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, in cod, navaga and hake, this figure does not exceed 4%. Such species are considered lean, or skinny. Sprat, mackerel, herring, saury, sturgeon and stellate sturgeon are considered the highest indicator for this trait. Their fat content is well above the 8% mark.
In commodity science, the concepts of "species" and "families" are used. Fish, the classification of fish are determined in trade practice most often on the basis of external signs. For example, the Herring family unites representatives who havethe body is laterally compressed, and the scales fall freely. These fish lack a lateral line. They have a single dorsal fin, and the caudal fin has a characteristic notch. This family includes herring, sprat, tyulka, 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 shown in the table.
| Features for comparison | Class Cartilaginous fish | Class Bony fish |
| Skeleton structure | Completely composed of cartilage | The skeleton includes bone tissue |
| Presence of gill covers | Absent, gill slits open outwards by independent openings | Present, protect the gills and participate in respiratory movements |
| Swim Bladder | Missing | Available |
| Type of fertilization and development | Internal, direct | Outer, indirect |
| Features of selection | The ducts of the digestive, reproductive and excretory systems are secreted into the cloaca | There is no cesspool, each organ system opens with its own opening |
Habitat
Classification of fish by habitat also defines several groups. The first is marine life. This is a flounderherring, 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.
Adromant fish
Classification of fish by habitat and lifestyle includes another group called Anadromous. 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.
Through such a difficult path, the representatives of the checkpoints lose a lot of strength. They have to swim against the current, overcome rapids, waterfalls. All this time they do not eat, but consume their own supply of fat and nutrients. Therefore, many migratory fish swim to the breeding ground, spawn and die. Already young individuals return to their permanent habitat. It is still a mystery how the 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, pink salmon grows a hump on its back, jaws are bent.
So, the classification of fish is based on several features. These include features of the skeleton and internal structure,size, fat content, habitat, lifestyle, use.
