When a person looks into the water from his familiar world filled with light and air, the world in which fish live seems to him cold, dark, mysterious, inhabited by many strange, unusual creatures. He himself in this environment can move only with great difficulty and in a very limited space. The need to put on heavy, bulky equipment in order to see, breathe, keep warm and move at a speed that should seem like a turtle to fish hides from humans some of the undoubted advantages of fish over land dwellers.

Advantages are given by the very existence in the aquatic environment, which played an important role in the formation of fish. Water is not subject to sharp temperature changes and therefore can serve as an excellent habitat for cold-blooded animals. Changes in water occur slowly and provide an opportunity to move to more suitable places or adapt to changing conditions. Weight maintenance problem own body in water is also much easier than on land, because protoplasm has about the same density as water, and therefore fish in their environment are almost weightless. And this means that they can get by with a simple and light skeleton and at the same time reach sometimes significant sizes. Such a huge fish as a whale shark moves with the same freedom and ease as a small guppy.

But there is one significant difficulty that is associated with life in water and which, more than anything else, has shaped fish, is the incompressibility of water. Everyone who has ever made their way through the water just above the ankle has felt the difficulty that the fish have to overcome all the time: when moving, the water must be moved apart, literally pushed aside, and it immediately closes behind you again.

Flat and angular bodies move with difficulty through such a medium (if you push a board lying on the water straight down, it will inevitably wag from side to side), so the body shape of the fish is remarkably consistent with this property of water. We call such a shape streamlined: sharply pointed from the head, most voluminous closer to the middle and gradually tapering towards the tail, so that the water can flow smoothly from both sides with the least turbulence and, when approaching the tail, even impart some additional impetus to the fast-swimming fish. Of course, there is a certain variety of shape, but in general this is the initial form for all free-swimming fish, no matter what shape they have acquired in the process of evolution.

The body of a fish, like that of any vertebrate animal, has bilateral mirror symmetry and is built according to the same simple scheme: a hollow cylinder with an alimentary tract open on both sides, which stretches inside from one end to the other. At the front end is the mouth opening, at the opposite end is the anal opening. Along the upper half of the cylinder runs the spinal column, a series of bony or cartilaginous discs that stiffen the entire structure. In the canal formed by the vertebrae is the spinal cord, which, expanding at the anterior end, forms the focal point, or brain. The walls of the cylinder along its entire length from head to tail are divided into numerous identical segments, the strong motor muscles of these segments act on the bone or cartilage skeleton and enable the entire body to make wave-like movements from side to side.

Since fish are cold-blooded animals, life in the aquatic environment, as already mentioned, is especially favorable for them, but still it has its limitations. When the temperature drops below what the fish can tolerate, they have to leave these places - which is why many temperate fish make seasonal migrations. With strong and abrupt change the temperatures of the fish become too lethargic and do not have time to leave, and if conditions do not improve, they die. Some freshwater fish, which, when the seasons change, cannot make migrations, bypass this danger, plunging into winter or summer hibernation - they stop eating and in winter time lie inertly on the bottom, and in the summer they burrow into the silt until the temperature is again favorable.

The circulatory system in fish is the simplest of all vertebrates. Blood passes one circle - from the heart through the gills, where it is saturated with oxygen, to various organs and parts of the body that take oxygen, and back to the heart. The heart itself consists of only two chambers, an atrium and a ventricle (unlike the three-chambered heart of amphibians and the four-chambered mammals), and works, so to speak, on the same line with the entire system.

A characteristic feature of fish is fins, large or small pterygoid formations that give them stability in the water, help them move and control movements. Most fish have two types of paired fins - pectoral, on the sides of the head immediately behind the gills, and ventral, which are usually pushed back. At the top, the dorsal fin passes through the middle of the back; it can be divided into two parts, the anterior spiny and the posterior soft. On the ventral side of the body behind the anus is the anal fin, and at the very end - the tail.

All fins have their own special purpose, they are all mobile and driven by muscles located inside the body of the fish. The dorsal and pectoral fins, acting together, perform leading role in building sustainability. The dorsal fin, pointing straight up, acts as a stabilizer to keep the fish upright; The pectoral fins are extended to the sides to help maintain balance and make turns. The pelvic fins are also used as stabilizers. The tail is used for control and in the most fast-moving fish it also plays the role of a stabilizer and an engine. The fish with force hits them from side to side, and all rear end her body makes undulating swimming movements. At fast swimmers the dorsal and anal fins are pressed against the body or even retracted into special recesses, which increases the streamlining.

The location and structure of the fins in fish can be very diverse. In most benthic species, the paired fins are very close together and the ventral pair, strongly shifted towards the head, is sometimes even in front of the pectoral fins, directly under the lower jaw. This arrangement allows you to keep the head and gills above the bottom surface. In other fish, the ventral fins are greatly reduced or even completely disappeared, for example, in eels. In triggerfish and other more or less discoid fish, the pectoral fins take on the role of engines in whole or in part. In the benthic gurnard, the lower rays of the pectoral fins are disconnected and act like the legs of an insect. And the pectoral fins of the striped lionfish serve it mainly for camouflage: their long and widely spread rays resemble a bunch of algae among the coral reefs where this fish lives.

The body shape of the fish also differ markedly from each other. The most amazing changes have occurred with those of them that lie at the bottom almost all the time: they have become flat. Some fish lie on their belly and are flattened from above, while others lie on their sides and are flattened laterally. Flattening in such fish occurs during the growth of juveniles and ends with an unusual process of moving the eyes to one, upper, side of the head. Winter flounder ( Pseudopleuronectus americanus), for example, lies on its left side, and its eyes are on its right side, while its close relative, the summer flounder ( Paralichthys dentatus), on the contrary, the eyes are on the left side, as it lies on the right side.

Among the fish, flattened from above, - angler. This fish rarely moves and catches its prey with its own lure rod - a fleshy lump on a thin flexible rod hanging from its head. His close relative, a sea clown, is more active: his pectoral fins have turned into a special kind of limbs, and with their help he moves in jumps.

A variety of stingrays are essentially sharks that have switched to a sedentary bottom life and become flat. While swimming, their wide pectoral fins make wave-like movements and the fish seem to float in the water. In many stingrays, the tail is extended like a whip and has no motive power.

Even in the water, there are other modes of transportation besides swimming, and fish use them all to varying degrees. They crawl along the bottom like gurnards and dol-gopers, and can even come out of the water onto the shore, like the mudskipper does. The Malayan Creeper and the Chinese Snakehead easily walk on the ground from pond to pond, crawling in exactly the same way as most fish swim. In order not to tip over, the crawler supports its narrow, brisk body with pectoral fins, like props.

Some fish can also move through the air, though for short distances. The Mississippi armored pike glides across the surface of the water, using its tail like an outboard motor propeller. But flying fish do fly - they can fly through the air for almost a full minute and, if a strong wind is blowing, they rise to a height of three to six meters and glide over the waves on large front fins extended like wings. There are biplane-type flying fish, those that use their pectoral and ventral fins to fly, there are monoplanes that fly only on their pectoral fins, and there are even freshwater species fish that fly like birds, flapping their pectoral fins over the water surface.

One remarkable feature of fish immediately attracts attention: from head to tail, fish are covered with a flexible, as a rule, shell of rounded bone plates, or scales, overlapping one another. These scales are fixed in the inner layer of the skin and form the protective cover necessary for the fish. In addition to the scale armor, the fish is also protected by a layer of mucus secreted by numerous glands scattered throughout the body. Mucus, which has antiseptic properties, protects the fish from fungi and bacteria, and also lubricates the surface of the body. Differences in the size and thickness of the scales can be very significant - from microscopic scales of an ordinary eel to very large, palm-sized scales of a three-meter long barbel that lives in Indian rivers. Only a few species of fish, such as lampreys, do not have scales at all. In some fish, the scales have merged into a continuous, immovable carapace like a box, like in boxfish, or formed rows of closely connected bone plates, like in seahorses and sea needles.

The scales grow as the fish grows, and some fish leave distinct annual and seasonal marks on the scales. The substance necessary for growth is secreted by a layer of skin covering the scales from the outside, and builds up along its entire edge. Since in temperate zones the scales grow fastest in the summer, when there is more food, it is sometimes possible to determine the age of the fish by the number of growth rings on the scales.

The mouth of a fish is the only tool for capturing food, and in all kinds of fish it is perfectly adapted for its work. The parrot fish, as has already been said, developed a real beak for pinching off plants and corals; the small American gerbil is equipped with a burrowing tool - a hard, sharp protrusion on the lower jaw, with which it digs in the sand in search of small crustaceans and worms.

In fish feeding near the surface, the mouth is usually directed upwards, the lower jaw is sometimes strongly elongated, as, for example, in half-snouts. Bottom-dwelling fish, such as stargazer and monkfish, which grab prey floating above them, also have their mouths pointing upwards. And in those fish that are looking for their food at the bottom, such as rays, haddock and common chukuchan, the mouth is located on the underside of the head.

Well, how do fish breathe? To maintain life, she, like all animals, of course, needs oxygen - in fact, her respiratory process is not so different from the breathing of land animals. To extract oxygen dissolved in water, fish drive water through the mouth, pass it through the gill cavity and push it out through the holes located on the sides of the head. The gills act in much the same way as the lungs. Their surface is permeated with blood vessels and covered with a thin layer of skin that forms folds and plates, the so-called gill filaments, which increase the absorption surface. The entire gill apparatus is enclosed in a special cavity, covered with a bone shield, gill cover.

The gill apparatus is distinguished by high functional adaptability, so that some fish can even obtain the oxygen they need not only from water, but also from atmospheric air. Common carp, for example, in hot summer months, when the pond dries up or lacks oxygen, it captures air bubbles and holds them in the mouth next to the moist gills. The creeper, snakehead and Indian catfish have special air cavities with folded walls near the gills. Lungfish, if necessary, use fully developed lungs with the same network of blood vessels as in frogs and newts. In some ancient fishes, the rudimentary lung, which later turned into a swim bladder, is still connected to the esophagus, and in essence these fish - siltfish, armored pike - have spare lungs.

However, the swim bladder modern fish, if present, no longer performs respiratory functions, but acts as an improved lifting balloon. The bladder is located in the abdominal cavity below the spine and is an airtight sac equipped with glands that can, if necessary, extract gas directly from the fish's bloodstream and fill the bladder with it. The amount of gas is regulated with great precision, and the fish gets just the lift it needs to stay on its usual horizon, whether near the surface or at a depth of four hundred meters. Many fish that live at great depths or lead a benthic lifestyle do not need a swim bladder, and they do not have one. The swim bladder limits the ability of fish to move arbitrarily to any depth, since adaptation to depth and pressure occurs gradually. Most fish living at considerable depths cannot rise to the surface, because their swim bladder would swell to an unbearable size for a fish - if such a fish is caught on a bait and pulled out of the water, the swollen bladder can squeeze out its stomach through the mouth. There are fish, such as the mackerel family, with a very small bladder or no bladder at all. For them, there is no such restriction, and they can forage at different depths. However, they pay dearly for this: in order not to drown, they need to be in constant motion.

There are fish that live alternately in fresh and salt water, they have special difficulties - salt barriers that they need to overcome. Because fish live in water, they need to maintain a balance between the salts dissolved in their blood and lymph and the salts that may or may not be present in the surrounding water. In freshwater fish, the concentration of salts in the blood is higher than in the surrounding waters, and therefore water always tends to penetrate the body of the fish through the skin, gill membranes, mouth and other open areas of the body. Under such unremitting pressure, the fish must constantly expel water in order to maintain proper balance. Marine fishes have just the opposite difficulty: they constantly give up water to a saltier environment and therefore must constantly absorb it in order not to shrink, as baked apple. And to isolate excess salts that enter along with water, marine fish have special cells on their gill filaments.

Since the aquatic environment is very different from the air environment, we are right to ask ourselves the question of how the fish use the senses to notify it of where it is and what is happening around. What does the fish see? How does she hear? Does she have a sense of smell like ours, a sense of taste, touch?

It can be answered that fish have all these five senses, and in addition they have another, truly sixth sense, which allows them to very subtly perceive the slightest change in the movement of water around. This sixth sense is unique to fish (This organ system is also characteristic of amphibians living in the water.), And its organs are located in the system of channels under the skin.

Let's start, however, with the organ of vision - it works in fish in the same way as in humans, with the difference that fish that feed themselves above the surface of the water have to deal with the phenomenon of refraction. Due to the refraction of light rays when they pass from air environment into water (or vice versa), objects observed in water seem to be displaced if you do not look at them directly from above. A man who wants to hit a fish with an arrow from a bow must aim far below where he sees it, otherwise he will miss, and long practice has taught him to do this. Likewise, trout, perch, or salmon, preparing to grab an insect fluttering over their pond, must jump out of the water a little ahead of the intended target - and for a very long time in the process of evolution this skill has turned into a reliable, instinct-based skill.

Fish foraging in the water do not have to overcome this difficulty, because light travels in a straight line underwater as it does in air. There are, however, other factors that affect the mechanism of visual perception in their underwater world, and hence the structure of their eyes. Chief among these factors are the amount of light available underwater and the limit of visibility due to the fact that even the clearest water cannot compare with air.

The lack of bright light in the underwater world has contributed to a significant simplification in the structure of the eye of most fish in comparison with the eyes of land animals: they can do with little or no contraction of the iris, they also do not need eyelids, because water is constantly washing away foreign particles from their eyes. . They have an iris - a metallic-colored ring around the dark pupil, but to regulate the amount of light rays entering the eye, it does not need to expand and contract to the same extent as our iris, so in most fish it is motionless.

Since visibility under water does not exceed thirty meters at best (and often much less), fish do not need to adjust their eyes to too large a difference in distances. Almost all the time they have to consider objects only in close proximity, and the device of their eyes corresponds to this. Their lens is not a lens with adjustable curvature, like the human eye, but an incompressible ball. In the normal position, the eye of the fish sees only close objects, and if you need to look at an object that is at a far distance, a special muscle pulls up the lens.

There is another, more important reason for the spherical shape of the fish lens, and this again has to do with refraction.

Since the lens contains a substance of almost the same density as water, light, penetrating from the surrounding aquatic environment into the lens, is not refracted - according to the laws of optics, this means that for a clear image of an object on the retina, the curvature of the lens must be significant, and the ball has the greatest curvature. But, according to some scientists, even with such a curvature, the image is not really clear, and it is possible that the fish, even under the most favorable conditions, does not see objects clearly enough under water.

But fish have an advantage that land animals don't have: they can see in more than one direction at the same time. Their eyes are not located in front, but usually on the sides of the head, and what each eye sees is recorded in the brain with opposite side, that is, objects on the right are fixed by the visual center located on the left side of the brain, and vice versa.

This fish's monocular vision has its limitations, especially in distance estimation. However, it is entirely possible that there is a relatively narrow space directly ahead of the fish that both eyes can see at the same time, hence fish have some degree of binocular vision (and hence a sense of perspective) such as we have. Indeed, when something aside attracts the attention of a fish, it seems to be really trying to replenish its monocular vision: it quickly turns so that the object is in the field of view of both eyes and it would be possible to better estimate the distance to it.


DOUBLE VISION. The eyeball of the four-eyed fish living in the rivers of Central and South America is designed so that the fish can simultaneously and equally clearly see both in the water and above its surface. Both eyes of the four-eyed are located at the top of the head, and she can swim, putting them half out of the water. True, from time to time she has to dive in order to moisten the upper, "above-water" part of the eye.

The extent to which fish can distinguish colors is unknown. Basic tone underwater world fish - greenish blue, since all other colors are absorbed and disappear already on short distance from the surface. The perception of color is therefore not especially important for fish. important; the only exceptions are those fish that swim near the surface. However, we do know that all fish except sharks can perceive some colors. Microscopic examination of the retina of fish showed that it contains cones, nerve cells, which distinguish colors, and rods, which function mainly at night and are insensitive to color.

But what significance color has in the daily life of fish remains a mystery. Some fish prefer one color to another: trout, for example, distinguishes artificial flies by color. If a darkened aquarium is illuminated with all the colors of the spectrum, the fish will swim towards the green and yellow bands and stop there, but if only red is left, they will behave as if in the dark.

Bright and sharply contrasting colors, of course, can be a certain means for fish to identify each other, but here again we are not sure that this is actually the case. Bright, colorful outfit of some tropical fish makes, naturally, to think that it must have some significance for other inhabitants of the underwater world. Does a shark, for example, recognize a pilot fish by the contrasting transverse stripes on its dark back and sides? This would explain to us why such a small fish, a little over twenty centimeters long, can fearlessly swim next to its huge and voracious companion, and he will never swallow it by mistake.

It is also possible that bright colors serve as an identification mark warning of the inedibility or poisonousness of fish. There are fish that are probably not good prey for other fish, and in the shallow waters of tropical coral reefs, where underwater visibility is relatively high, the bright coloration that distinguishes them so sharply from their underwater counterparts can serve as a protection.

In any case, it seems likely that some species of fish recognize each other by color. In their greenish-blue world, a bright color catches the eye faster than a gray, barely noticeable shadow that flickers somewhere nearby. This conjecture is supported by the fact that most fish species, usually swimming in dense flocks, are rarely brightly colored, while fish living apart, among a rather uniform color environment, as a rule, have a conspicuous appearance, and other individuals of this species can recognize them.

The dyes themselves are produced by a layer of cells in the skin under transparent scales. These cells are called chromatophores, or color carriers, and contain a variety of pigment grains.

These are primarily orange, yellow and red pigments, very similar to the pigments in a red or yellow flower. Then the black pigment, which is essentially an unnecessary waste of the body and can be found not only in the skin (the internal organs of black-skinned fish also, as a rule, have a black shell), and finally, the substance guanine, contained in the form of crystals, which, depending on their numbers and arrangements can produce white, silver, or iridescent colors. In combination with a black pigment, guanine gives blue and green metallic tints.

Of course, the main thing in the coloring of most fish is its protective properties. The protective coloration of fish that live in the upper layers of the sea - a dark back and a white or silvery bottom - makes them hardly noticeable from wherever you look at them. The camouflage of bottom fish is very skillful - their color matches the color of the bottom or, like the zigzag pattern of camouflaged warships, breaks the contours of the fish's body. To this “tearing” coloration, the so-called “deceptive” color is added, which completely changes the appearance of the fish.

Sometimes surrounding objects are imitated not only in color, but also in shape. The Amazonian leaf fish surprisingly resembles a leaf floating in the water. Fish can even change their disguise at different periods of life - in tropical waters off the coast of Florida, for example, there are fish that at a young age take the shape and color of a mangrove pod lying on a white sandy bottom, but when they outgrow, so to speak, a pod, this disguise becomes useless, the fish then go into deeper waters, becoming striped. One of the most skillful masters of camouflage is the common flounder; with the ease of a chameleon, it imitates stones, sand, dark silt.

Camouflage can even affect the structure of the fish. The Sargasso sea clown is covered with skin-like outgrowths like threads and patches imitating algae, where it hides, and in the seahorse-rag-picker, long processes look like sea grass leaves, which it clings to.

Most fish retain the same basic color throughout their lives, but in some it changes with age. Young salmon and trout are streaked with dark stripes, while in adult fish the stripes disappear. Male salmon, trout, stickleback and many other fish change their color during the breeding season. Once, Dr. William Beebe discovered coral fish that changed color combinations seven times in a day.

Even males and females can differ in their coloration. The male gudgeon, or lyre fish, and the European wrasse look like exotic birds with brilliant plumage, while the females of both species are completely inconspicuous. There are fish that night time become darker or, like barracuda, take on a completely different color. Many fish change color when frightened or caught on a hook.

After death, the color of the fish usually changes immediately and often becomes completely different from what it was during life. The most amazing changes occur, perhaps, with a bright green-gold dolphin, or sea bream. During the death agony, the green and gold colors turn into blue and pure white, and then gradually, when the last convulsions stop, the whole body takes on a dull brownish-olive hue.

For a long time, scientists have studied the hearing of fish, trying to find out if they can perceive sounds. It was believed that they could not, but what we call the ear serves in fish simply as an organ of balance. But since some fish still make sounds underwater (these can be calls and response signals during the mating season or identification signals), it is logical to conclude that they still perceive them. Most likely, when perceiving sound waves, the swim bladder serves as a resonator. Since they do not have a tympanic membrane and auditory ossicles of the inner ear, which represent the real hearing apparatus of higher animals, it is believed that the role of the hearing organ, which perceives sound in the form of wave vibrations, in some fish is played by the swim bladder and the so-called Weberian apparatus - a series of small bones connecting the swim bladder to the inner ear. Some fish are certainly very sensitive to fluctuations, including the simple movement of water. They can hear the sound of a propeller at a great distance, and the steps of a person on the shore, quite slightly shaking the ground and thus the water, are quite enough to frighten trout in a pond. Touch sensitivity in fish is carried out by nerve endings distributed throughout the skin. Most of them are on the head and around the lips, and in many fish they are located, in addition, on special antennae. Cod and red mullet explore the bottom with rather short antennae sitting on their chins; catfish have very long whiskers.

Almost all fish are characterized by a finely developed sense of smell. They have nostrils somewhat similar to ours - a pair of small recesses that open outward and are located directly on the snout, lined inside with folded tissue, which greatly increases their surface. This tissue contains nerve cells that perceive smell.

The sense of smell in most fish is so developed that when looking for food it means much more to them than sight. Sharks can smell blood from afar and appear near a wounded fish or animal out of nowhere. Athlete anglers have successfully used fish blood to attract bluefish and other predatory fish. If you pour only one glass of water into the pool with lampreys, in which another fish swam, the lampreys will immediately become alert and begin to look for the source of this aroma that has suddenly appeared pleasant to them.

As for taste sensitivity, it probably does not play a big role in the life of fish. First of all, none of them, except for lungfish, have taste organs in their mouths. They have taste buds, but they are located on the head, trunk, tail, modified fins or antennae, and therefore, if the fish taste food, it happens before it gets into their mouth. Many fish simply swallow food, it goes directly to the stomach and is digested there.

The most remarkable feature of the fish is its unique "sixth sense", which allows it to subtly perceive all the movements and currents of water. The most perfectly arranged system of channels under the skin is quite clearly marked on the sides of the fish as a series of scales of a different shape from the rest. This is the side line. In the main channel at a certain distance from each other are located specialized bodies feelings. The same channels diverge throughout the head.

Scientists have yet to uncover all the mysteries of the lateral line, but it is already clear that its main function is related to capturing the movement of water. If the base of the nerve that runs from the lateral line to the brain is cut, then the fish quite obviously loses the ability to respond to disturbances in the water or a change in the direction of the flow. Apparently, it is this special sense organ that allows the coral fish to shoot like an arrow through a narrow crevice, which it probably does not see properly, or makes it possible for fish to bypass obstacles invisible in muddy water during floods. And, probably, it is the lateral line that allows huge fish schools of many thousands of individuals to swim in such a coordinated formation.

Anyone who has ever fished, or seen others fish, must have wondered if fish feel pain. This question is too difficult to give a definite answer to it. Pain is not only a physical reaction, but also a mental one, and we cannot learn from the fish what exactly it feels. But we can be almost sure that mentally fish do not feel pain.

Well, do they feel pain physically? In humans, pain is born in the cerebral cortex as a result of information sent by sensory nerves, but fish do not have a formation comparable to the human cortex, or any other part of the brain that would perform its functions.

The strength of irritation of certain sense organs, necessary in order to cause a sensation of pain, is called the pain threshold. In some species of animals, as well as in individual individuals, it is much higher than in others. The lower we go down the evolutionary ladder, the higher the pain threshold becomes, the more irritation is needed to cause a pain reaction. We can be pretty sure that it is high in fish. In response to too much irritation, they simply walk away or try to walk away.

That's why a fish can safely swim away with a hook in its mouth or a harpoon in its back, and a wounded shark will continue to attack even if its brethren rip out its insides.

Pisces class- This is the most numerous group of modern vertebrates, which unites more than 25 thousand species. Fish are inhabitants of the aquatic environment, they breathe with gills and move with the help of fins. Fish are common in different corners planets: from high-altitude reservoirs to ocean depths, from polar waters to equatorial ones. These animals inhabit the salty waters of the seas, are found in brackish lagoons and estuaries. major rivers. They live in fresh rivers, streams, lakes and swamps.

The external structure of the fish

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

The internal structure of fish

Fish organ systems

1. Skull (consists of the brain case, jaws, gill arches and gill covers)

2. The skeleton of the body (consists of vertebrae with processes-arcs and ribs)

3. Skeleton of fins (paired - pectoral and ventral, unpaired - dorsal, anal, caudal)

1. Brain protection, food capture, gill protection

2. Protection of internal organs

3. Movement, balance

musculature

Wide muscle bands divided into segments

Movement

Nervous system

1. Brain (sections - anterior, middle, oblong, cerebellum)

2. Spinal cord (along the spine)

1. Movement control, unconditioned and conditioned reflexes

2. Implementation of the simplest reflexes, conduction of nerve impulses

3. Perception and conduction of signals

sense organs

3. Organ of hearing

4. Touch and taste cells (on the body)

5. Lateral line

2. Smell

4. Touch, taste

5. Feeling the direction and strength of the current, the depth of immersion

Digestive system

1. Digestive tract (mouth, pharynx, esophagus, stomach, intestines, anus)

2. Digestive glands (pancreas, liver)

1. Capturing, grinding, moving food

2. secretion of juices that contribute to the digestion of food

swim bladder

Filled with a mixture of gases

Adjusts the immersion depth

Respiratory system

Gill filaments and gill arches

Carry out gas exchange

Circulatory system (closed)

Heart (double-chambered)

arteries

capillaries

Supply of all cells of the body with oxygen and nutrients, removal of decay products

excretory system

Kidneys (two), ureters, bladder

Isolation of decay products

Breeding system

In females: two ovaries and oviducts;

In males: testes (two) and vas deferens

The figure below shows the main systems internal structure fish

Fish Class Classification

Currently living fish are divided into 2 main classes: cartilaginous fish and bony fish. Important distinctive features cartilaginous fish - 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. The most common among them are sharks and rays.

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

The main groups of Pisces

Squads of fish

The main features of the detachment

Representatives

Cartilaginous skeleton, no swim bladder, no gill covers; predators

Tiger shark, whale shark, katran

Manta, stingray

Sturgeons

Osteo-cartilaginous skeleton, scales - five rows of large bone plates, between which there are small plates

Sturgeon, beluga, sterlet

Dipnoi

They have lungs and can breathe atmospheric air; notochord preserved, no vertebral bodies

Australian horned tooth, African flake

Crossopterygians

The skeleton mainly consists of cartilage, there is a notochord; poorly developed swim bladder, fins in the form of fleshy outgrowths of the body

Latimeria (the only representative)

Cypriniformes

Mostly fresh water fish, no teeth on the jaws, but there are pharyngeal teeth for grinding food

Carp, crucian carp, roach, bream

herring

Most are flocks sea ​​fish

Herring, sardine, sprat

Cod

A distinctive feature is the presence of a mustache on the chin; most are cold-water marine fish

Haddock, herring, na-vaga, burbot, cod

Ecological groups of fish

Depending on the habitat, they are distinguished environmental groups fish: freshwater, anadromous, brackish and marine.

Ecological groups of fish

Main features

freshwater fish

These fish constantly live in fresh water. Some, such as carp and tench, prefer stagnant water. Others, such as the common minnow, grayling, chub, have adapted to life in the flowing waters of rivers.

migratory fish

This includes fish that migrate from sea water to fresh water for breeding (for example, salmon and sturgeon) or from fresh water go to breed in salty (some types of eels)

brackish fish

They inhabit desalinated areas of the seas, the mouths of large rivers: such are many whitefish, roach, goby, river flounder.

sea ​​fish

They live in the salt water of the seas and oceans. The water column is inhabited by fish such as anchovy, mackerel, tuna. At the bottom live stingray, flounder.

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

Chapter 8 Fish products

8.1. The structure of the body of fish and types of cutting fish
Test 8.1.1. The structure of the body of fish

Name the body parts of the fish marked in the picture.
Figure 8.1. The structure of the fish

Test 8.1.2. Types of fish cutting

Select from the list of types of cutting the type corresponding to each definition.

Definitions:

1. a fish whose pectoral fins have been removed along with the adjacent part of the abdomen and part of the viscera;

2. a fish whose entrails and caviar or milk have been removed through an incision in the abdomen;

3. a fish with a head removed with a bundle of viscera, without an incision on the abdomen;

4. a fish that has had its head, belly and entrails removed. The head may be left;

5. a fish that has had its gills or gills and part of its entrails removed;

6. decapitated or decapitated gutted fish with the tail fin removed;

7. decapitated gutted fish, cut along the spine into two longitudinal halves, from which the fins, tail, belly, spine, humerus and costal bones have been removed;

8. longitudinal halves cut from a fish carcass parallel to the backbone;

9. part of a fish carcass, cut across;

10. The fish is cut along the abdomen with two longitudinal cuts: the first one is from the anus to the ventral fins, the second one is from the ventral fins to the fin (part of the body of the fish located between the gill covers and pectoral fins). Removed gills, entrails, caviar or milk;

11. abdominal part of fish;

12. fish, cut along the back along the spine from upper lip to the caudal fin, from which the insides, caviar or milk have been removed.

Types of fish cutting:

a) sidebar b) gilled; c) chaffy; d) a piece; e) decapitated; f) reservoir; g) gutted; h) gutted salmon; i) back j) comfort;

k) carcass; m) fillet.

Note. This task can also be used as a constructive test of the second level, if you do not provide students with a list of types of fish cutting.

8.2. Main commercial families fish
Test 8.2.1. Fish families: external signs

(first level, test ratio)

Establish the relationship between the families of fish and their characteristic external features.

Fish families:

1. flounder;

2. carp;

3. salmon;

4. perch;

5. sturgeons;

6. herring;

7. mackerels;

8. catfish;

9. cod;

10. pike.

Distinctive external features:

a) the body is elongated, spindle-shaped. There are two fins on the back. After the second dorsal fin and after the anal fin, additional small fins run towards the tail;

b) the body is fusiform with small scales, there are two fins on the back, the first of them is ordinary, and the second is prickly;

c) the body is flat, the upper side of the body with scales, the lower side without scales, the eyes are located on the upper side of the body;

d) elongated, fusiform body with a well-marked lateral line. They have three dorsal fins and two anal fins.

e) the body is oblong, covered with scales, there are no scales on the head. There is one regular fin on the back and an additional adipose fin closer to the tail;

f) the body is elongated, laterally compressed, the scales are small, the lateral line is not visible. Caudal fin with deep notch;

g) the body is slightly elongated, in most members of the family it has a high thickened back. The scales are large with a well-marked lateral line;

h) the body is large, without scales. Large head with a wide mouth and whiskers;

i) the body is elongated with small scales, the snout is elongated, flattened from top to bottom, with sharp teeth. Body color is spotted. The dorsal fin is located closer to the tail;

j) an elongated body with an elongated snout, without scales, five rows of bone growths along the body. The tail fin is asymmetrical.

Test 8.2.2. Fish families: representatives

(first level, test ratio)

Choose from a list of fish belonging to each of the named families.

Fish families:

1. flounder;

2. carp;

3. salmon;

4. perch;

5. sturgeons;

6. herring;

7. mackerels;

8. cod.

a) vobla; b) beluga; c) pink salmon; d) ruff; e) crucian carp; e) chum salmon; g) sea language; h) navaga; i) halibut; j) blue whiting; l) herring; m) sardine; m) stellate sturgeon; o) zander; n) sterlet; p) tuna; c) heck.

8.3. Live, chilled, frozen fish
Test 8.3.1. Live, chilled, frozen fish

1. Which of the following families of fish is not usually sold live?

a) mackerels;

b) cyprinids;

c) sturgeons;

d) pike.

2. What color should be the gills of a quality live fish?

a) pink

b) red;

c) yellowish;

d) whitish.

3. What factors do not affect the preservation of the quality of live fish when kept in aquariums in a store?

a) water temperature;

b) the workload of the aquarium;

c) composition of water;

d) availability of food.

4. What temperature does chilled fish usually have in the thickness of the muscles?

5. What kind of chilled fish is not produced?

a) undivided;

b) gutted with a head;

d) gutted headless.

6. How is chilled fish classified according to quality indicators?

a) first and second grades;

7. What temperature does frozen fish usually have in the thickness of the muscles?

a) not higher than - 25°;

b) not higher than - 18°;

c) not higher than - 12°;

d) not higher than - 8°.

8. How is fish frozen in modern factories?

a) in bulk and blocks;

b) individually and in blocks;

c) individually, in bulk and in blocks;

d) only in blocks.

9. How is frozen fish classified according to quality indicators?

a) first and second grades;

b) the highest, first, second grade;

c) first, second, third grades;

d) is not divided into varieties.

10. What determines the shelf life of frozen fish?

a) the type of fish;

b) on the type of cutting of fish;

c) on the method of freezing;

d) all of the above.

Test 8.3.2. Live, chilled, frozen fish

1. Freshwater fish are usually sold live, such as ... (Name at least five types of fish).

2. The surface of live fish must be clean, with a thin layer ... .

3. A weak fish, swimming on its side or belly up, is called ....

4. The term for the sale of live fish in the store ..., while the fish ... in order to avoid water pollution.

5. Chilled fish is packed in a container with ....

6. A sour smell in the gills is allowed, which is easily removed by washing with water, in all chilled fish, except ....

7. Frozen fish is made in unglazed and glazed form. Glaze is...

8. Frozen fish, depending on the quality indicators, is divided into the first and second grades, the indicators are determined by .... (Specify when).

9. The consistency of frozen fish must be dense, in the second grade it can be ..., but not ....

10. If a block of fish is defrosted to 0° (to facilitate the separation of fish from each other), the implementation period is reduced to ... days.

8.4. Salty fish
Test 8.4.1. Salted and dried fish

(first level, test-identification)

Choose the correct answer from the multiple options provided.

1. Which family of fish is usually not salted?

a) herring;

b) perch;

c) salmon;

d) anchovies.

2. What is used in spicy salting of fish besides salt?

a) only black pepper and bay leaf;

b) a mixture of various spices;

c) a mixture of various spices and sugar;

d) a mixture of spices, sugar and acetic acid.

3. What kind of ambassador is called "special ambassador"?

a) sweet ambassador;

b) pickled ambassador;

c) spicy salt;

d) the ambassador of especially valuable fish.

4. By what principle is a salted herring usually given a trade name?

a) by the size of herrings;

b) by the name of the fishing vessel;

c) by the time of the catch;

d) according to the habitat of herring.

5. How are salted herring subdivided depending on quality indicators?

a) the highest, first, second grade;

b) first and second grades;

c) first, second, third grades;

d) are not divided into varieties.

6. Under what method of salting does the fish have the most dense texture?

a) the consistency of the fish does not depend on the method of salting;

b) wet salting;

c) dry salting;

d) mixed ambassador.

7. What determines the shelf life of salted fish?

a) the type of container and packaging;

b) on the type of cutting of fish;

d) all of the above.

8. Which family of fish is most often used for drying?

a) carp;

b) mackerels;

c) herring;

d) cod.

Test 8.4.2. Salty fish

(second level, test substitution)

Insert missing words.

1. A solution of salt in water, used for salting, and a brine released from fish tissues is called ....

2. Depending on the nature of the changes taking place in the body of the fish during salting, the fish are divided into ....

3. Depending on the method of introducing salt into the fish, salting happens ....

4. Depending on the recipe, the ambassador is ....

5. Depending on the capacity, the ambassador is ....

6. Depending on the salt content, salted herrings are divided into ....

7. The consistency of salted fish depends on its salt content: the higher the salt content, the more consistency ... .

8. For salted salmon fish of the second class, a slight smell is allowed ... ... on the surface.

8.5. Smoked fish and balyk products
Test 8.5.1. Smoked fish

(first level, test-identification)

Choose the correct answer from the multiple options provided.

1. Which type of smoked fish usually has a firmer texture?

a) cold smoking;

b) hot smoked;

c) the consistency of the fish does not depend on the method of smoking.

2. Which type of smoked fish tends to taste less salty?

a) cold smoking;

b) hot smoked;

c) the taste of fish is the same in terms of salinity.

3. Which type of smoked fish is usually tied with twine?

a) cold smoking;

b) hot smoked;

c) both cold and hot smoked.

4. How is hot-smoked fish classified by quality?

a) for the highest and first grade;

b) for the first and second grades;

d) is not divided into varieties.

5. How is cold-smoked fish classified by quality?

a) for the highest and first grade;

b) for the first and second grades;

c) for the highest, first and second grades

d) is not divided into varieties.

6. What deviation from quality is allowed by the standard for hot smoked fish?

a) slight signs of dampness;

b) broken heads and tail fins;

c) small burns on the surface;

d) all of the above.

7. What quality deviation is not allowed for cold-smoked fish?

a) salt deposits on the surface;

b) light spots not covered by smoke;

c) iodine smell in marine fish;

d) flabby texture.

8. Which type of smoked fish has the longest shelf life?

a) cold smoking;

b) hot smoked;

c) the shelf life does not depend on the method of smoking.

9. Why only certain families of fish (sturgeon, salmon, some oceanic fish) are used to make balyk products?

a) for balyk products use only rare species fish;

b) for balyk products, only fish with a certain body shape are used;

c) only fatty fish species are used for balyk products;

d) for all of the above reasons.

10. What other method of processing fish, besides cold smoking, is used in the manufacture of balyk products?

a) drying;

c) hot smoking:

d) all of the above.

Test 8.5.2. Smoked fish

(second level, test substitution)

Fill in the missing words and numbers.

1. They hoard fish with smoke or ....

2. Depending on temperature regime smoking can be ... and ....

3. Cold smoking of fish is carried out at a temperature of ... for ... .

4. Hot smoking of fish is carried out at a temperature of ... for ... .

5. The consistency of hot-smoked fish should be from juicy to dense, but ... is allowed.

6. Cold-smoked fish, depending on the quality indicators, is divided into varieties: ....

7. The color of cold-smoked fish can be from light golden to ....

8. Smoked fish with the following defects is not allowed for sale: ... . (Name at least three defects).

9. Balyk products are prepared from fish of the following families: ..., some oceanic fish are also used, for example, .... (Name at least two types of fish).

10. For the preparation of balyk products, such types of fish cutting are used as .... (Name at least three types of cutting).

8.6. Fish caviar
Test 8.6.1. Fish caviar

(first level, test-identification)

Choose the correct answer from the multiple options provided.

1. What size are sturgeon eggs?

a) 1 - 2 mm;

b) 2 - 4 mm;

c) 4 - 6 mm;

d) 1 - 6 mm depending on the size of the fish.

2. What size are salmon eggs?

a) 1 - 6 mm depending on the size of the fish;

b) 2 - 4 mm;

c) 3 - 6 mm;

d) 1 - 2 mm.

3. What determines the shade of the color of caviar of fish belonging to the same family?

a) the age of the fish;

b) from the time of spawning;

c) from the fatness of the fish;

d) the type of fish.

4. What type of processing can sturgeon caviar be subjected to?

a) pasteurization;

b) sterilization;

c) ultra-pasteurization;

d) all of the above.

5. For what purpose is vegetable oil added to salmon caviar when preparing it?

a) to improve the taste of eggs;

b) to preserve the color of the eggs;

c) to prevent sticking of eggs;

d) all of the above.

6. What varieties are divided into canned salmon granular caviar depending on the quality indicators?

a) highest, first, second;

b) first, second;

c) first, second, third;

d) is not divided into varieties.

7. What varieties are divided into canned sturgeon granular caviar depending on the quality indicators?

a) highest, first, second;

b) first, second;

c) first, second, third;

d) is not divided into varieties.

8. What deviations from ideal quality are allowed in salmon and sturgeon caviar?

a) the presence of shells of bursting eggs;

b) slight bitterness;

c) taste of silt;

d) all of the above.

Test 8.6.2. Fish caviar

(second level, constructive test)

Answer the questions.

1. What is the name of the organ in female fish that contains caviar?

2. At what period of a fish's life is caviar mature?

3. What color and size is sturgeon caviar?

4. What color and size is salmon caviar?

5. What color and size is the caviar of other commercial fish, such as cod, pollock, pike, capelin, etc.?

6. Name the varieties of sturgeon caviar, depending on the characteristics of its production.

7. Name the variety of salmon caviar, depending on the characteristics of its production.

8. What kind of caviar is called granular? What are the features of its preparation?

9. What are the features of the appearance of pressed caviar? What kind of eggs is it usually prepared from?

10. What kind of caviar is called breakdown? What are the features of the preparation of breakdown delicacy caviar?

11. What are the requirements for the appearance of granular salmon and sturgeon caviar in the standards?

12. What is the main raw material for making artificial caviar?

8.7. Non-fish objects
Test 8.7.1. Non-fish objects

(first level, test classification)

Divide the listed representatives into groups.

Groups:


1. crustaceans;

2. cephalopods;

3. bivalve molluscs;

4. echinoderms;

5. seaweed.

Representatives:

a) squids; b) cuttlefish; c) crabs; d) shrimp; e) krill; e) cucumaria; g) kelp; h) spiny lobsters; i) mussels; j) sea scallops; l) sea ​​urchins; m) lobsters; m) octopuses; o) river crayfish; n) trepangs; p) oysters.

Test 8.7.2. Non-fish objects

(second level, constructive test)

Answer the questions.

1. In what parts of the body is edible meat found in crustaceans?

2. What are large sea crayfish called?

3. Which representative of crustaceans has smallest dimensions, and how is it used?

4. What types of frozen shrimp are produced depending on the type of processing?

5. What is the main raw material for making crab sticks?

6. What are the structural features of cephalopods?

7. What is edible in bivalves?

8. What is eaten by sea urchins?

9. What is the official name for "seaweed"?

10. How are seaweed-derived substances such as agar, agaroid, furcellaran used?

8.8. Canned fish and preserves
Test 8.8.1. Canned fish and preserves

(first level, test-identification)

Choose the correct answer from the multiple options provided.

1. What type of fish is natural canned food made from?

a) from raw fish;

b) from boiled fish;

c) from fried fish;

d) all of the listed types.

2. What filling is not used in the manufacture canned fish?

a) broth

b) tomato sauce;

c) melted butter;

d) vegetable oil.

3. What type of pre-treatment does the fish go through in the manufacture of canned food "Sprats in oil"?

a) drying

b) frying;

c) smoking;

d) blanching.

4. Which of the listed items of canned food is divided into varieties according to quality?

a) "Fish in jelly";

b) "Sprat in tomato sauce";

c) "Natural Far Eastern salmon";

d) "Sprats in oil".

5. What is the name of a defect in a metal can with canned food, when the lid or bottom is deformed in the form of corners at the seam?

a) "bird";

b) "tick";

c) "rook";

d) forty.

6. How can an assortment sign be indicated on a metal can with canned fish?

a) letters of the Russian alphabet;

b) letters of the Latin alphabet;

c) a combination of letters and numbers;

d) all of the above.

7. What family of fish is most often used for making preserves?

a) flounder;

b) herring;

c) perch;

d) mackerels.

a) -12…-18°;

Test 8.8.2. Canned fish and preserves

(second level, constructive test)

Answer the questions.

1. What are the main technological operations in the manufacture of canned food that make them suitable for long-term storage?

2. What methods of preliminary heat treatment of fish are used in the preparation of canned food? (Name at least three types of processing).

3. What is the name of canned food made from raw fish without additives or with the addition of spices?

4. What fillings are used in the manufacture of canned fish? (Name at least three types of fills).

5. What internal organs of fish can be used to make canned food?

6. What types of canned food are made in the form of a homogeneous crushed mass? (Name at least two types of canned food).

7. What non-fish objects (seafood) are used to make canned food? (Give at least three examples.)

8. What is the main difference between canned fish and vegetable and canned fish and vegetables?

9. Containers from what materials are used in the manufacture of preserves?

10. Why preserves, unlike canned food, should be stored at a temperature not higher than 0 °?

Fish common in all types of water bodies, from marine water spaces to the smallest ponds, eriks and rivers. Tropics and eternal ice are also rich in unusual varieties of fish. In the waters of Russia aquatic life very diverse and distinguished by their beauty. In the territory 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, more than 450 fish species, and many live permanently, and some arrive temporarily until a certain period.

general information

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

Gills absorb oxygen from the water and release carbon dioxide, ammonia, urea and other waste products into the water. At bony fish four gill arches on each side.

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

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

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

AB - commercial length of fish; AB - standard size; 1 - gill cover; 2 - dorsal fin hard; 3 - soft dorsal fin; 4 - tail fin; 5 - side 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 things of groups I, II or III. A number of fish species listed in the standard are not subdivided according to length and weight. The smallest length of fish that is allowed to be caught is set by fishing regulations and international conventions.

IN commodity practice Fish are classified according to species and families.

A species is a collection of individuals occupying a certain geographical area and having a number of inherited traits that distinguish this species from closely related species. Species close in a number of characteristics are combined into genera, and the latter into families.

IN trade practice classification of fish by families is carried out mainly according to external features. Strictly scientific classification of fish by families is made according to many features. The characteristics of the main features of the families of fish most commonly found in commercial practice are given below.

herring family has a laterally compressed body, covered with easily falling scales. Lateral line is absent. The dorsal fin is single, the caudal fin is deeply notched. Herring is of commercial importance: Atlantic, Pacific, Danube, Don, Dnieper, Kerch, Volga, Chernospinka, Azov shad, Salaka, Sardines, Sardinella, Sardinops (Ivasi); sprats: Caspian, Baltic (sprats), Black Sea, Tyulka.

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

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

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

salmon family has a high body, laterally compressed, covered with small scales. There are two dorsal fins, the second 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, an incomplete lateral line. There are two dorsal fins, the second is adipose. Main species: European smelt, smelt, capelin.

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

scad family has a flattened body shape. Lateral line with a sharp bend in the middle, in some species covered with bony spines. There are two dorsal fins, the first is prickly, the second is soft and long. There are two spines in front of the anal fin. The tail stalk is thin. The horse mackerels of the Azov-Black Sea, oceanic, caranx, seriola, pompano, lychia, vomer are of commercial importance.

cod family subdivided into subfamilies of cod-like and burbot-like. The former have three dorsal and two anal fins, the latter 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 or in front, many representatives have a mustache on the chin.

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

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

According to the shape of the body and the arrangement of the fins, tuna, bonito, mackerel 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. Commercial value halibut black, common, arrow-toothed; flounder sharp-headed and river.

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

sea ​​bass golden, beaked, Pacific from the scorpion family have big head, oblong, laterally compressed body, often red in color, one dorsal fin, often prickly in the anterior part.

catfish striped and spotted from the catfish family

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

Terpugi northern, southern, toothed 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, since it contains copper instead of iron.

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

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

Slab, captain, umbrina- fish from the croaker family, have a high body, a humpback in front of the back, one dorsal fin, divided by a deep notch, the anterior part is prickly, the lateral line is well expressed.

grenadiers from the macrourid family, they have an elongated, fading body in the tail section in the form of a thread. There are two dorsal fins.

They also catch such species of fish as catfish, pike, lamprey, eel, gobies, Argentina, mullet, eelpout, prystipoma, bluefish from families with similar names, sea bream from the Brahm family; merrow, rock perch- from the Serranaceae family.