Fish. Description of fish

We present a list of the most common freshwater (river) fish. Names with photos and descriptions for each river fish: its appearance, the taste of the fish, habitats, fishing methods, time and method of spawning.

Pike perch, like perch, prefers only clean water, saturated with oxygen and conducive to the normal functioning of the fish. This is pure fish without any ingredients. The growth of pike perch can be up to 35 cm. Its maximum weight can reach up to 20 kg. Pike perch meat is light, without excess fat and very tasty and pleasant. It contains quite a lot of minerals, such as phosphorus, chlorine, chlorine, sulfur, potassium, fluorine, cobalt, iodine, and also a lot of vitamin P. Judging by the composition, pike perch meat is very healthy.

Bersch, like pike perch, is considered a relative of perch. It can grow up to 45 cm in length, weighing 1.4 kg. It is found in rivers that flow into the Black and Caspian Seas. Its diet includes small fish, like a gudgeon. The meat is almost the same as that of pike perch, although a little softer.

Perch prefers reservoirs with clean water. These can be rivers, ponds, lakes, reservoirs, etc. Perch is the most common predator, but you will never find it where the water is turbid and dirty. To catch perch, they use rather thin gear. Catching it is very interesting and entertaining.

The ruff has a peculiar appearance with the presence of very spiny fins, which protects it from predators. The ruff also loves clean water, but depending on its habitat it can change its color. It grows no more than 18 cm in length and gains weight up to 400 grams. Its length and weight directly depend on the food supply in the pond. Its habitat extends to almost all European countries. It is found in rivers, lakes, ponds and even seas. Spawning takes place over 2 days or more. The ruff always prefers to be at depth, as it does not like sunlight.

This fish is from the perch family, but few people know it, since it is not found in this area. It is distinguished by an elongated fusiform body and the presence of a head with a protruding snout. The fish is not large, no more than one foot long. It is found mainly in the Danube River and its adjacent tributaries. Its diet includes various worms, mollusks and small fish. The chop fish spawns in April with bright yellow eggs.

This is a freshwater fish that is found in almost all bodies of water on the globe, but only in those that have clean, oxygenated water. When the oxygen concentration in the water decreases, the pike dies. Pike grows up to one and a half meters in length, weighing 3.5 kg. The body and head of the pike are characterized by an elongated shape. It’s not for nothing that it’s called an underwater torpedo. Pike spawning occurs when the water warms up from 3 to 6 degrees. It is a predatory fish and feeds on other species of fish such as roach, etc. Pike meat is considered dietary because it contains very little fat. In addition, pike meat contains a lot of protein, which is easily absorbed by the human body. Pike can live up to 25 years. Its meat can be stewed, fried, boiled, baked, stuffed, etc.

This fish lives in ponds, lakes, rivers, and reservoirs. Its color is largely determined by the composition of the water that is available in a given reservoir. In appearance it is very similar to the rudd. The roach's diet includes various algae, larvae of various insects, as well as fish fry.

With the arrival of winter, the roach goes to wintering pits. It spawns later than pike, around the end of spring. Before spawning begins, it becomes covered with large pimples. The caviar of this fish is quite small, transparent, with a green tint.

Bream is an inconspicuous fish, but its meat is characterized by excellent taste. It can be found where there is calm water or a weak current. Bream lives no more than 20 years, but grows very slowly. For example, a 10-year-old specimen can gain weight no more than 3 or 4 kilograms.

Bream has a dark silvery tint. The average life expectancy is 7 to 8 years. During this period, it grows up to 41 cm in length and has an average weight of about 800 g. Bream spawns in the spring.

This is a sedentary fish species with a bluish-gray color. The silver bream lives for about 15 years and grows to a length of up to 35 cm, with a weight of 1.2 kg. Silver bream, like bream, grows quite slowly. They prefer bodies of water with standing water or slow currents. In spring and autumn, the silver bream gathers in numerous flocks (dense flocks), hence its name. The silver bream feeds on small insects and their larvae, as well as mollusks. Spawning occurs at the end of spring or beginning of summer, when the water temperature rises to +15ºС-+17ºС. The spawning period lasts from 1 to 1.5 months. Silver bream meat is considered not tasty, especially since it contains a lot of bones.

This fish has a dark yellow-golden hue. It can live up to 30 years, but already at 7-8 years its growth stops. During this time, the carp manages to grow up to 1 meter in length and gain a weight of 3 kg. Carp is considered a freshwater fish, but it is also found in the Caspian Sea. Its diet includes young shoots of reeds, as well as eggs of spawned fish. With the arrival of autumn, its diet expands and begins to include various insects and invertebrates.

This fish belongs to the carp family and can live for about a hundred years. May eat undercooked potatoes, bread crumbs or cake. A distinctive feature of cyprinids is the presence of a mustache. Carp is considered a voracious and insatiable fish. Carp lives in rivers, ponds, lakes, and reservoirs where there is a muddy bottom. Carp likes to pass pliable silt through its mouth, in search of various bugs and worms.

Carp spawns only when the water begins to warm up to a temperature of +18ºС-+20ºС. Can gain weight up to 9 kg. In China it is a food fish, and in Japan it is a decorative food.

A very strong fish. Many experienced fishermen fish for it, using powerful and reliable gear.

Crucian carp is the most common fish. It is found in almost all bodies of water, regardless of the quality of the water and the concentration of oxygen in it. Crucian carp is able to live in reservoirs where other fish will immediately die. It belongs to the carp family, and in appearance it is similar to carp, but does not have a mustache. In winter, if there is very little oxygen in the water, crucian carp hibernate and remain in this state until spring. Crucian carp spawns at a temperature of about 14 degrees.

Tench prefers ponds with dense vegetation and covered with thick duckweed. Tench can be caught well from August, before the onset of real cold weather. Tench meat has excellent taste characteristics. It’s not for nothing that tench is called the king’s fish. In addition to the fact that tench can be fried, baked, stewed, it makes an incredible fish soup.

The chub is considered a freshwater fish and is found exclusively in rivers with fast currents. It is a representative of the carp family. It grows up to 80 cm in length and can weigh up to 8 kg. It is considered a semi-fat fish, since its diet consists of fish fry, various insects, and small frogs. It prefers to be under trees and plants hanging over the water, since various living creatures very often fall into the water from them. It spawns at temperatures from +12ºС to +17ºС.

Its habitat includes almost all rivers and reservoirs of European countries. Prefers to stay at depth in the presence of a slow current. In winter it is as active as in summer, as it does not hibernate. It is considered a fairly hardy fish. It can have a length from 35 to 63 cm, with a weight from 2 to 2.8 kg.

Can live up to 20 years. The diet consists of both plant and animal foods. Spawning of ide occurs in the spring, at water temperatures from 2 to 13 degrees.

It is also a representative of the family of carp fish species and has a dark bluish-gray color. It grows up to 120 cm in length and can reach a weight of 12 kg. Found in the Black and Caspian Seas. Selects areas with fast currents and avoids stagnant water.

There are saberfish with silver, grayish and yellow colors. It can gain weight up to 2 kg, with a length of up to 60 cm. It can live for about 9 years.

Chekhon grows very quickly and gains weight. Found in rivers, lakes, reservoirs and seas such as the Baltic Sea. At a young age it feeds on zoo- and phytoplankton, and with the arrival of autumn it switches to feeding on insects.

It is easy to confuse rudd and roach, but rudd has a more attractive appearance. Over the course of 19 years of life, it is able to gain weight of 2.4 kg, with a length of 51 cm. It is found, for the most part, in rivers that flow into the Caspian, Azov, Black and Aral seas.

The basis of the rudd's diet is food of plant and animal origin, but most of all it likes to eat caviar of mollusks. Quite a healthy fish with a set of minerals such as phosphorus, chromium, as well as vitamin P, proteins and fats.

The podust has a long body and chooses areas with fast currents. It grows up to 40 cm in length and weighs up to 1.6 kg. The podust lives for about 10 years. It feeds from the bottom of the reservoir, collecting microscopic algae. This fish is distributed throughout Europe. Spawns at a water temperature of 6-8 degrees.

Bleak is a ubiquitous fish, known to almost any person who has fished with a fishing rod in a pond at least once. Bleak belongs to the family of carp fish species. It can grow to small sizes in length (12-15 cm) with a weight of about 100 grams. It is found in rivers flowing into the Black, Baltic and Azov Seas, as well as in large bodies of water with clean, non-stagnant water.

This is a fish, the same as bleak, but slightly smaller in size and weight. With a length of 10 cm, it can weigh only 2 grams. Able to live up to 6 years. It feeds on algae and zooplankton, but grows very slowly.

It also belongs to the family of carp fish species, and it has a spindle-shaped body shape. It grows in length up to 15-22 cm. It is carried out in reservoirs where there is a current and there is clean water. The gudgeon feeds on insect larvae and small invertebrates. It spawns in the spring, like most fish.

This type of fish also belongs to the carp family. It feeds practically on food of plant origin. It can grow up to 1 m 20 cm in length and weigh up to 32 kg. It has high growth rates. Grass carp is distributed throughout the world.

The diet of silver carp consists of microscopic particles of plant origin. It is a large representative of the carp family. This is a heat-loving fish. The silver carp has teeth that are capable of grinding vegetation. It is easy to acclimatize. Silver carp is grown artificially.

Due to the fact that it grows quickly, it is of interest for industrial breeding. Can gain up to 8 kg of weight in a short time. It is mostly distributed in Central Asia and China. Spawns in the spring, loves water areas where there is an intense current.

This is a very large representative of freshwater bodies, capable of growing up to 3 meters in length and weighing up to 400 kg. The catfish is brown in color but has no scales. Inhabits almost all reservoirs of Europe and Russia, where appropriate conditions exist: clean water, the presence of aquatic vegetation and suitable depth.

This is a small representative of the catfish family that prefers small reservoirs (canals) with warm water. In our time, it was brought from America, where there is quite a lot of it and most fishermen fish for it.

Its spawning occurs in conditions when the water temperature reaches +28ºС. Therefore, it can only be found in the southern regions.

This is a fish from the family of river eels and prefers freshwater bodies of water. This is a snake-like predator that is found in the Baltic, Black, Azov and Barents seas. Prefers to be in areas with a clay bottom. Its diet consists of small animals, crayfish, worms, larvae, snails, etc. Capable of growing up to 47 cm in length and gaining weight up to 8 kg.

This is a heat-loving fish that is found in reservoirs located in large climatic zones. Its appearance resembles that of a snake. A very strong fish that is not so easy to catch.

It is a representative of the codfish and is similar in appearance to a catfish, but it does not grow to the size of a catfish. This is a cold-loving fish that leads an active lifestyle in winter. Its spawning also occurs in the winter months. It hunts mainly at night, while leading a bottom-dwelling lifestyle. Burbot is an industrial fish species.

This is a small fish with a long body covered with very small scales. It can easily be confused with an eel or a snake if you have never seen one in your life. It grows up to 30 cm in length, or even more if growth conditions are favorable. It is found in small rivers or ponds with a muddy bottom. It prefers to be closer to the bottom, and can be seen on the surface during rain or thunderstorms.

Char belongs to the salmon family of fish species. Due to the fact that the fish does not have scales, it got its name. Grows to small sizes. Its meat does not decrease in volume under the influence of low temperatures. Characterized by the presence of fatty acids, such as omega-3, that can resist inflammatory processes.

It lives in rivers and feeds on various types of fish. Distributed in rivers of Ukraine. Prefers non-deep water areas. It can grow up to 25 cm in length. It reproduces by caviar at water temperatures within +8ºС. After spawning, it can live no more than 2 years.

The lifespan of this fish is considered to be about 27 years. It grows in length up to 1 m 25 cm, gaining weight up to 16 kg. It is distinguished by its dark gray-brown color. In winter, it practically does not feed and goes into the depths. It has valuable commercial value.

This fish lives only in the Danube basin and is not common anywhere else. It belongs to the family of salmon fish species and is a unique representative of the fish fauna of Ukraine. Danube salmon is listed in the Red Book of Ukraine and fishing for it is prohibited. It can live up to 20 years and feeds mainly on small fish.

It also belongs to the salmon family and prefers rivers with rapid currents and cold water. It grows in length from 25 to 55 cm, while gaining weight from 0.2 to 2 kg. The trout diet includes small crustaceans and insect larvae.

It is a representative of the Eudushidae family, reaches a size of about 10 cm, while gaining a weight of 300 grams. It is found in the basins of the Danube and Dniester rivers. At the first danger, it buries itself in the mud. Spawning occurs in March or April. Likes to feed on fry and small invertebrates.

This fish is caught on an industrial scale in Edver and the Urals. Spawns at temperatures no higher than +10ºС. This is a predatory fish species that loves fast-flowing rivers.

This is a freshwater species of fish that belongs to the carp family. It grows up to 60 cm in length and gains up to 5 kg of weight. The fish is dark in color and is distributed in the Caspian, Black and Azov seas.

River fish without bones

Virtually no bones:

• In maritime language.
• In fish of the sturgeon family, belonging to the order Chordata.

Despite the fact that water has a certain density, the body of the fish is ideally suited for movement in such conditions. And this applies not only to river fish, but also to sea fish.

Typically, its body has an elongated, torpedo-like body shape. In extreme cases, its body has a spindle-shaped shape, which facilitates unhindered movement in the water. Such fish include salmon, podust, chub, asp, sabrefish, herring, etc. In still water, most fish have a flat body, flattened on both sides. Such fish include crucian carp, bream, rudd, roach, etc.

Among the many species of river fish there are both peaceful fish and real predators. They are distinguished by the presence of sharp teeth and a wide mouth, which allows them to swallow fish and other living creatures without much difficulty. Similar fish include pike, burbot, catfish, pike perch, perch and others. A predator such as a pike is capable of developing enormous initial speed during an attack. In other words, it literally swallows its prey instantly. Predators such as perch always hunt in schools. Pike perch leads a bottom-dwelling lifestyle and begins hunting only at night. This indicates his uniqueness, or rather his unique vision. He is able to see his prey in complete darkness.

But there are also small predators that do not have large mouths. Although, such a predator as the asp does not have a huge mouth, such as a catfish, for example, and it feeds only on young fish.

Many fish, depending on their habitat conditions, can have different shades. In addition, different reservoirs may have different food supplies, which can significantly affect the size of the fish.

Fish are cold-blooded vertebrates that belong to the multicellular subkingdom, the phylum Chordata. They managed to adapt to a wide variety of environmental conditions. They live both in freshwater and saltwater reservoirs, up to 10 thousand meters deep, and in dry river beds with water from 2 to 50 degrees, etc. Their body temperature is almost equal to the temperature of the water in which they live, and does not exceed it by more than 0.5 - 1 C (tuna fish species can have a difference that is much larger, up to 10 C). Thus, the environment affects not only the speed of digestion, but also the shape of the body, which is divided into the following types:

• fusiform ( sharks);
• flattened in bottom inhabitants ( stingrays, flounders);
• streamlined, torpedo-shaped in individuals that spend most of their lives in the water column ( mullet, tuna);
• sagittal ( pike);
• spherical ( bodies).

Despite the external and internal differences formed by the habitat, the structure of the fish has common characteristics. Like all vertebrates, they have a skeleton with muscles, skin, an excretory system, reproductive, sensory and respiratory organs, a digestive, nervous and circulatory system.

Skeleton and musculature

Most fish have a bony or cartilaginous skeleton, but there are also individuals with a cartilaginous skeleton. For example, shark, stingray. Based on this, a logical question follows: How does the structure of bony fish differ from cartilaginous fish?

Structure of bony fish

Muscles are naturally attached to the bones of the skeleton, which form the musculature. The strongest muscles in fish are located in the tail, for obvious reasons, and on the dorsal side of the body. Thanks to muscle contraction, the fish reproduces movement.

The structure of cartilaginous fish

Fins

For many bony fish A formula is compiled based on the nature and presence of rays in the fins. It is widely used in identifying and describing fish species. In the formula, the Latin abbreviation for the fin designation is given:

A– (from the Latin language pinna analis) anal fin.
D1, D2 – (pinna dorsalis) dorsal fins. Roman numerals indicate prickly ones, and Arabic numerals indicate soft ones.
P – (pinna pectoralis) pectoral fin.

V – (pinna ventralis) ventral fin.

When a fish swims, the driving force comes from the tail and caudal fin. They are the ones who push the fish’s body forward with a powerful blow. The tail swimmer is supported by special flattened bones (for example, urostyle, which is translated from Greek as stick, support, etc.). The anal and dorsal fins help the fish maintain balance. The rudder is the pectoral fins, which move the fish’s body during slow swimming, and together with the caudal and ventral fins, it helps to maintain balance when the fish is not moving.

In addition, fins can perform completely different functions. For example, in viviparous individuals, the anal, modified fin became the mating organ. Gouramis have filiform pelvic fins in the form of tentacles. There are species of fish with sufficiently developed pectoral fins that allow them to jump out of the water. Other individuals that burrow into the ground often have no fins at all.

The tail fins have the following types:

• Truncated;
• Round;
• Split;
• Lyre-shaped.

Skin covering

In most fish, the body is covered with protective formations - scales, which are cartilaginous or bone formations consisting of 50% organic substances and 50% inorganic substances, such as calcium phosphate, sodium, magnesium phosphate and calcium carbonate. Microminerals are also present in the scales.

The habitat and features of the external structure of fish affect the variety of shapes, sizes and number of scales in different species. Some may have virtually no scales at all. Others have large scales. For example, in some carp they can reach a couple of centimeters. However, in general, the body size of a fish is directly proportional to its scales and is determined by the linear equation:

Of course, the environment and lifestyle directly influence the structure of the scales. So, for example, swimmer fish, which spend most of their lives in motion, have developed, strong scales, which help reduce body friction with the water and also impart speed.

Specialists stand out three types of scales:

• bony (divided into cycloid - smooth, rounded and ctenoid, which has small spines along the posterior edge);
• ganoid,
• placoid.

Bone scale It is characterized by the presence of only bone substance in its composition. The following fish species have it: herring, carp, and perch.

Placoid scales found in fossil fish. It is the most ancient and, like the ganoid, is a diamond shape, but with a spike that protrudes outward. The chemical composition of the scales is dentin, and the spike is covered with special enamel - vitrodentin. A special feature is that this type of scale is characterized by a cavity that is filled with loose connective tissue with nerve fibers and even blood vessels. Modified placoid scales are also possible, for example, the spines of stingrays. In addition to stingrays, sharks also have placoid scales. It is typical for cartilaginous fish.

The scales on the body are arranged in a row; the number does not change with age, and therefore sometimes serves as a species characteristic. For example, the lateral line of pike has 111-148 scales, and crucian carp - 32-36.

Excretory system

Venous blood enters this organ through the portal veins of the kidneys, and arterial blood through the renal arteries.

The morphophysiological element is the tortuous renal urinary canal, in which one end increases in the Malpighian corpuscle, and the other goes to the ureter. Products of nitrogenous breakdown, namely urea, enter the lumen of the tubules and are secreted by glandular cells. There, the reabsorption of microelements and all kinds of vitamins from the filtrate of Malpighian corpuscles (a glomerulus of arterial capillaries, which is covered by the enlarged walls of the tubule and creates Bowman’s capsule), sugars and, of course, water occurs.

The filtered blood flows back into the kidney's vascular system, the renal vein. And urea and metabolic products exit through the tubule into the ureter, which in turn pours into the bladder or, in other words, the urinary sinus, and then the urine comes out. For a huge number of fish, the final breakdown product is ammonia (NH3).

Marine species drink water and excrete excess salts and ammonia through their kidneys and gills. Freshwater fish species do not drink water; it continuously enters the body and is excreted through the urogenital opening in males and through the anus in females.

Reproductive organs

The female lays eggs, which the male fertilizes with seminal fluid. After the incubation period, the eggs hatch into larvae, which initially feed on the yolk sac.

On the structural features of cartilaginous fish can be considered internal fertilization. Most of them have a cloaca. Males (males) have several pelvic fins, which form the copulatory organ. By nature, cartilaginous fish are egg-laying or viviparous.

Sense organs

Smell and taste

Not everyone knows that fish have a well-developed taste organ. They determine salty, sweet, sour and bitter tastes. Taste buds are located along the edges of the jaws, in the oral cavity and on the antennae. Fish that do not have antennae have a poorly developed taste.

Vision

The lens of a fish's eye, compared to a human's, is elastic (not able to change shape) and quite hard. In an unexcited state, it is located near the cornea and allows the fish to see at a distance of up to 5 meters in a straight line. When viewing at a greater distance, the lens moves away from the cornea and, with the assistance of the ligaments, approaches the retina. This allows the fish to see up to 15 meters in the water, which is quite shocking. By the size of the eye, which correlates with the fish’s head, one can determine visual acuity and the ability to see the world around us.

The back part of the retina, thanks to special cells - cones (allow you to see daylight) and rods (perceive twilight), recognizes color. Pisces are able to distinguish shades, approximately in the same range as humans. However, in comparison with humans, they also see the short-wavelength region of the spectrum, which the human eye does not perceive. Fish are also more sensitive to warm colors: yellow, red and orange.

What structural features distinguish amphibians from fish?

In the diagram you can see that each shade of the solar spectrum is characterized by a certain wavelength, while the vision of fish and humans is not equally sensitive to light with different wavelengths, that is, to a variety of colors. The relative susceptibility to light of different wavelengths at low light intensity is also shown. At high levels, the sensitivity shifts towards longer wavelengths. The amount of daylight penetrating under the surface of the water, of course, depends on the angle of incidence of it on the surface of the water, as well as on how strongly the surface of the water fluctuates, that is, agitated. Light rays are partially absorbed by water and some of them are scattered by solid microscopic particles that are suspended in water. The rays that penetrate the entire layer of water and reach the bottom are partially absorbed and partially reflected.

The visual perception of fish is also influenced by other factors, such as the purity and speed of water flow, and the line of refraction of light.

Side line

Of particular importance for fish is the lateral line canal system, which communicates with the external environment through openings. The lateral line stretches along the fish’s body and is capable of perceiving water vibrations, the presence of objects in the fish’s path, the speed and direction of currents. Even a blind fish is able to navigate space quite well.

Ear

The inner ear of fish consists of three semicircular canals, which are actually the organ of balance, and a sac that perceives sound vibrations.

Electric organs

Some species of cartilaginous fish have an electrical organ. It is intended for protection, orientation and signaling in space, as well as for attack. This paired organ is located on the sides of the body, or near the eyes, and consists of electric plates (modified cells) arranged in columns that generate electric current. In each such column, the plates are connected in series, but the columns are connected in parallel. The number of records in general amounts to hundreds of thousands, and sometimes millions. The discharge frequency depends on the purpose and is up to hundreds of hertz, and the voltage is up to 1200V. By the way, electrical discharges from fish such as eels and stingrays are dangerous to human life.

Respiratory system

Some individuals have additional respiratory organs in addition to gills. So, for example, in fish of the Anabantidae family, which includes many popular representatives of the aquarium ichthyofauna ( macropods, gourami, lalius), have a special organ - the gill labyrinth. Thanks to it, fish are able to absorb oxygen from the air. Moreover, if this family for some reason cannot rise to the surface of the water for several hours, then it dies.

The amount of oxygen required for the life of fish can vary. It depends on the water temperature, the size and type of fish, as well as the degree of their activity.

It is no secret that the solubility of gases decreases as the temperature of the liquid increases. The oxygen content in water that comes into contact with atmospheric air is usually less than the solubility limit:
0.7 milliliters per 100 grams of water at 15 C;
0.63 milliliters at 20 C;
0.58 milliliters at 25 C;

This ratio is sufficient for the inhabitants of the aquarium. Moreover, from 0.55 milliliters to 0.7 milliliters per 100 grams of water is optimal and beneficial for most fish species.

Digestive system

The digestive system includes: the mouth and oral cavity, pharynx, esophagus, stomach, intestines (large, small and rectum, ending with the anus). Certain species of fish have a cloaca in front of the anus, i.e. the cavity in which the rectum will appear, as well as the ducts of the reproductive system and urinary system.

The mouth opening of a fish is necessary for receiving, sometimes chewing and swallowing food. There are no salivary glands, but the taste buds, which were written about earlier, are present. Some species are equipped with a tongue and teeth. Teeth can be located not only on the jaws, but also on the palatal bones, pharynx and even tongue. Usually they do not have roots and are replaced by new ones over time. They serve to capture and hold food, and also perform a protective function.

Herbivores mostly do not have teeth.

From the oral cavity, food passes through the esophagus into the stomach, where it is processed using gastric juice, the main components of which are hydrochloric acid and pepsin. However, not all individuals have a stomach; these include: many gobies, cyprinids, monkfish, etc. Predators mainly have this organ.

Moreover, in different species of fish, the stomach may differ in structure, size and even shape: oval, tubes, letter V, etc.

In some herbivorous species, symbiotic protozoa and bacteria take part in the digestion process.

The final processing of food is carried out in the intestines with the help of secretions secreted by the liver and pancreas. It starts in the small intestine. The pancreatic ducts and the bile duct flow into it, which deliver enzymes and bile to the intestine, which break down proteins into amino acids, fats into fatty acids and glycerol, and polysaccharides into sugars.

In addition to the process of breaking down substances in the intestines, due to the folded structure of the walls, they are absorbed into the blood, which flows intensively in the posterior region.

The intestine ends with the anus, which is usually located at the end of the body, immediately in front of the genital and urinary openings.

The digestive process in fish also involves glands: the gallbladder, pancreas, liver and ducts.
The nervous system of fish is much simpler than that of higher vertebrates. It includes the central and associated autonomic (sympathetic) and peripheral nervous systems.

The CNS (Central Nervous System) includes the brain and spinal cord.

The nerves that branch from the brain and spinal cord to the organs are called the peripheral nervous system.

The autonomic nervous system is the nerves and ganglia that innervate the muscles of the blood vessels of the heart and internal organs. The ganglia are located along the spine and are connected to the internal organs and spinal nerves. Intertwined, the ganglia unite the central nervous system with the autonomic nervous system. These systems are interchangeable and independent of each other.

The central nervous system is located along the entire body: the part of it that is located in a special spinal canal formed by the upper arches of the spine forms the spinal cord, and the spacious anterior lobe, surrounded by a bone or cartilaginous skull, forms the brain.

The brain has five sections: the cerebellum, midbrain, medulla oblongata, diencephalon and forebrain. The gray matter of the forebrain, in the form of striped bodies, is located at the base and in the olfactory lobes. It analyzes the information that comes from the olfactory organs. In addition, the forebrain controls behavior (stimulates and participates in the vital processes of fish: spawning, school formation, territory defense and aggression) and movement.

In fish, the cerebellum and midbrain are best developed.

Midbrain includes the largest volume. It has the shape of two hemispheres. Each lobe is a primary visual center that processes signals from the organs of taste, vision, and perception. There is also a connection with the spinal cord and cerebellum.

Cerebellum has the appearance of a small tubercle, which is adjacent to the medulla oblongata from above. However, it is also found in large sizes, for example, in catfish and mormius.

The cerebellum is primarily responsible for proper coordination of movements and maintaining balance, as well as muscle work. It is connected to the lateral line receptors and synchronizes the work of other parts of the brain.

Medulla smoothly passes into the dorsal and consists of white-gray matter. It regulates and controls the functioning of the spinal cord and autonomic nervous system. Also important for the circulatory, musculoskeletal, respiratory and other systems of fish. If this part of the brain is damaged, the fish immediately dies.

Like many other systems and organs, the nervous system has a number of differences depending on the type of fish. For example, individuals may have different levels of formation of the lobes of the brain.

Structural features of representatives of the class cartilaginous fish (rays and sharks) include: olfactory lobes and developed forebrain. Bottom-dwelling and sedentary individuals have a small cerebellum and well-developed medulla oblongata and forebrain, because the sense of smell plays an important role in their life. In fast-swimming fish, the cerebellum is well developed, which is responsible for the coordination of movement, and the midbrain is responsible for the visual lobes. But in deep-sea individuals, the visual lobes of the brain are weak.

The continuation of the medulla oblongata is the spinal cord. Its peculiarity is that it quickly regenerates and recovers when damaged. There is gray matter inside, white matter outside.

The spinal cord serves as a conductor and receiver of reflex signals. Spinal nerves branch from it, which innervate the surface of the body, the muscles of the trunk, through the internal organs and ganglia.

In bony fish The spinal cord contains the urohypophysis. Its cells produce a hormone that takes part in water metabolism.

The most famous manifestation of the nervous system of fish is the reflex. For example, if fish are fed for a long time in the same place, they will preferentially swim there. In addition, fish can develop reflexes to light, vibration and temperature of water, smell and taste, as well as shape.

It follows from this that, if desired, an aquarium fish can be trained and develop certain behavioral reactions in it.

Circulatory system

In addition, fish have low blood pressure and a low heart rate: from 17 to 30 beats per minute. However, at low temperatures it can decrease to 1-2. Fish that survive freezing into ice during the winter season do not have a heart pulsation at all during this period.

Another difference in the circulatory system of mammals and fish is that the latter have a small amount of blood. This is explained by the horizontal position of the fish’s life activity, as well as by the habitat where the force of gravity affects the body much less than in the air.

The heart of fish is two-chambered and consists of one atrium and ventricle, conus arteriosus and sinus venosus. Fish have only one circle of blood circulation, except for lobe-finned fish and lungfish. Blood moves in a vicious circle.

From the ventricle comes the abdominal aorta, from which four pairs of delivery branchial arteries branch. These arteries in turn break up into capillaries, in which the blood is enriched with oxygen. Oxidized blood flows through the efferent branchial arteries into the roots of the dorsal aorta, which is divided into the internal and external carotid arteries, which merge into the dorsal aorta, and from it into the atrium. Thus, all body tissues are saturated with maximally oxygenated blood.

Erythrocytes (red blood cells) of fish contain hemoglobin. They bind carbon dioxide in tissues and organs, and oxygen in the gills. Depending on the type of fish, the capacity of hemoglobin in the blood may vary. For example, fast-swimming individuals living in water bodies with a good oxygen content have cells with an excellent ability to bind oxygen. Unlike red blood cells in mammals, in fish they have a nucleus.

If arterial blood is enriched with oxygen (O), it is colored bright scarlet. Venous blood, which is saturated with carbon dioxide (CO2) and poor in oxygen, is dark cherry.

It is noteworthy that the fish body has the ability to form hematopoiesis. Most organs, such as the spleen, kidneys, gill apparatus, intestinal mucosa, vascular endothelium and the epithelial layer of the heart, lymphoid organ, can create blood.

At the moment, 14 fish blood group systems have been identified.

Fish They are common in all types of reservoirs, from marine waters to the smallest ponds, eriks and rivulets. The tropics and eternal ice are also rich in unusual species of fish. In the reservoirs of Russia, aquatic inhabitants are very diverse and distinguished by their beauty. On the territory of the Russian Federation there are more than 120 thousand rivers, about 2,000,000 lakes, 12 seas, 3 oceans, and all of them are habitats fish. Even in fresh Russian reservoirs, over 450 animals have adapted to live. fish species, and many live permanently, and some arrive temporarily until a certain period.

general information

Based on the presence and nature of rays in the fins of most bony fishes, a fin formula is compiled, which is widely used in their description and definition. In this formula, the abbreviated designation of the fin is given in Latin letters: A - anal fin (from the Latin pinna analis), P - pectoral fin (pinna pectoralis), V - ventral fin (pinna ventralis) and D1, D2 - dorsal fins (pinna dorsalis). Roman numerals indicate the numbers of prickly rays, and Arabic numerals indicate the numbers of soft rays.

The gills absorb oxygen from the water and release carbon dioxide, ammonia, urea and other waste products into the water. Bony fish have four gill arches on each side.

Gill rakers are thinnest, longest and most numerous in fish that feed on plankton. In predators, the gill rakers are sparse and sharp. The number of rakers is counted on the first arch, located immediately under the gill cover.

The pharyngeal teeth are located on the pharyngeal bones, behind the fourth branchial arch.

Fish are classified according to a number of characteristics: lifestyle, fishing season, sex, physiological state, fatness, feeding pattern, length or weight.

AB - fishing length of fish; AB - standard size; 1 - gill cover; 2 - hard dorsal fin; 3 - soft dorsal fin; 4 - caudal fin; 5 - lateral line; 6 - anal fin; 7 - anus; 8 - ventral fins; 9 - pectoral fins

The length of the fish is measured in a straight line from the top of the snout to the beginning of the middle rays of the caudal fin (Fig. 20). Some small and low-value fish are classified as small fish of groups I, II or III. A number of fish species listed in the standard are not subdivided by length and weight. The minimum length of fish that can be caught is set by fishing regulations and international conventions.

IN commodity practice fish are classified by species and families.

A species is a collection of individuals that occupy a certain geographical area and have a number of inherited characteristics that distinguish this species from related species. Species that are similar in a number of characteristics are grouped into genera, and the latter into families.

IN trading practices Classification of fish into families is carried out mainly by external characteristics. Strictly scientific classification of fish into families is carried out according to many characteristics. Characteristics of the main characteristics of the families of fish most often found in commercial practice are given below.

Herring family has a laterally compressed body, covered with easily falling scales. There is no lateral line. There is one dorsal fin, the caudal fin has a deep notch. Herrings of commercial importance are: Atlantic, Pacific, Danube, Don, Dnieper, Kerch, Volga, Chernospinka, Azov belly, Herring, Sardines, Sardinella, Sardi-nops (Ivasi); sprat: Caspian, Baltic (sprats), Black Sea, Tyulka.

Anchovy family has a cigar-shaped body, similar in size to small herrings. This family includes the Azov-Black Sea Hamsa and Anchovy.

Sturgeon family has an elongated fusiform body, with five rows of bone formations - beetles: two abdominal, two thoracic, one dorsal. Elongated snout, With four antennae. The dorsal fin is single, the caudal fin is unequally lobed. Of commercial importance are: beluga, kaluga, sturgeon, thorn, stellate sturgeon, sterlet. By crossing beluga and sterlet, Soviet scientists obtained a bester, which is bred in reservoirs.

Carp family has a tall, laterally compressed body, covered with tightly fitting scales, sometimes naked. The dorsal fin is one, soft, the lateral line is well defined, the teeth are pharyngeal. This family includes fish of inland waters: carp, carp, crucian carp, roach, roach, ram, bream, white-eye, bluefish, barbel, silver carp, grass carp, buffalo, vimba, shemaya.

Salmon family has a tall body, laterally compressed, covered with small scales. There are two dorsal fins, the second one is adipose. The lateral line is well defined. Chum salmon, pink salmon, sockeye salmon, Chinook salmon, Caspian salmon, salmon, trout, whitefish, vendace, muksun, and omul are of commercial importance.

Family smelt has an oblong body shape, with easily falling scales, and an incomplete lateral line. There are two dorsal fins, the second one is adipose. Main species: European smelt, smelt, capelin.

Perch family has two dorsal fins, the first is spiny, the anal fin has three spiny rays, the lateral line is straight, and there are transverse stripes on the sides. Common species: perch, pike perch, ruff.

Horse mackerel family has a flattened body shape. The lateral line has a sharp bend in the middle, and in some species is covered with bony spines. There are two dorsal fins, the first is spiny, the second is soft and long. There are two spines in front of the anal fin. The tail stalk is thin. The Azov-Black Sea, Oceanic, trevally, seriola, pompano, Lichia, and Vomer horse mackerels are of commercial importance.

Cod family are divided into subfamilies of cod-like and burbot-like. The former have three dorsal and two anal fins, the latter have two dorsal and one anal. These are marine fish, with the exception of burbot. They have a well-defined lateral line. The pelvic fins are located under the pectoral fins or in front, and many representatives have a barbel on the chin.

The body shape is close to torpedo-shaped. Cod, haddock, navaga, pollock, pollock, blue whiting, burbot, and cod are of commercial importance.

Mackerel family has an elongated fusiform body and a slender caudal peduncle. There are two dorsal fins; behind the second dorsal and anal fins there are four to seven additional fins. Black Sea, common, and Japanese mackerels are of commercial importance. Mackerels are sold under the names “Azov-Black Sea mackerel”, “Far Eastern mackerel”, “Kuril mackerel”, “Atlantic mackerel”.

In terms of body shape and arrangement of fins, tuna, bonito, and mackerel fish are similar to mackerel; the latter have one dorsal fin and additional fins.

Flounder family has a flat body, flattened from the back to the abdomen, the eyes are located on one side of the head. Dorsal and anal fins along the entire length of the body. The commercially important halibuts are black, common, and arrow-toothed; sharp-headed and river flounder.

Of the fish of other families, the following are of commercial importance.

Groupers golden, beaked, Pacific from the scorpionfish family have a large head, an oblong, laterally compressed body, often red in color, one dorsal fin, usually spiny in the front.

Catfish striped and spotted from the catfish family

They have one long soft dorsal fin, a large round head, and the body in the back is laterally compressed.

Terpugi northern, southern, toothy have a spindle-shaped body, one spiny dorsal fin, highly developed anal and pectoral fins.

Ice fish from the white-blooded family, it has a large head with an elongated snout, two lateral lines, the color is light green, the blood is colorless, as it contains copper instead of iron.

Butterfish and butterfish small fish from the Stromatoid family they have a flattened high body, one soft long dorsal fin of the same size and shape as the anal fin, the lateral line follows the curve of the ridge.

Marbled and green notothenia, squama, toothfish from the notothenia family have a large head, two spiny dorsal fins, a long anal fin, large pectoral fins, and the body is thickened in the front.

Croaker, captain, umbrina- fish from the croaker family, have a high body, a humpbacked back in front, one dorsal fin, divided by a deep notch, the front part is spiny, the lateral line is well defined.

Macruruses from the grenadier family they have an elongated body that tapers off at the tail in the form of a thread. There are two dorsal fins.

Other types of fish that are caught are catfish, pike, lamprey, eel, gobies, argentina, mullet, eelpout, pristipoma, bluefish from families that have similar names, sea bream from the brahmin family; merrow, rock perch - from the serranaceae family.

Pisces class- this is the largest group of modern vertebrates, which unites more than 25 thousand species. Fish are inhabitants of the aquatic environment; they breathe through gills and move with the help of fins. Fish are distributed in different parts of the planet: from high mountain reservoirs to ocean depths, from polar waters to equatorial ones. These animals inhabit the salty waters of the seas and are found in brackish lagoons and the mouths of large rivers. They live in freshwater rivers, streams, lakes and swamps.

External structure of fish

The main elements of the external body structure of a fish are: head, operculum, pectoral fin, ventral fin, body, dorsal fins, lateral line, caudal fin, tail and anal fin, this can be seen in the figure below.

Internal structure of fish

The figure below shows the main systems of the internal structure of fish

Fish class classification

Living fish are divided into two main classes: cartilaginous fish and bony fish. Important distinguishing features of cartilaginous fish are the presence of an internal cartilaginous skeleton, several pairs of gill slits that open outward, and the absence of a swim bladder. Almost all modern cartilaginous fish live in the seas. Among them, the most common are sharks and rays.

The vast majority of modern fish belong to the class of bony fish. Representatives of this class have an ossified internal skeleton. A pair of external gill slits are covered with gill covers. Many bony fish have a swim bladder.

Main orders of Pisces

Ecological groups of fish

Depending on their habitat, ecological groups of fish are distinguished: freshwater, anadromous, brackish and marine.

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A source of information: Biology in tables and diagrams./ Edition 2, - St. Petersburg: 2004.