Biology at the Lyceum. Organs of movement - fins The meaning of the dorsal fin in fish

The habitat of fish is all kinds of bodies of water on our planet: ponds, lakes, rivers, seas and oceans.

Fish occupy very vast territories; in any case, the ocean area exceeds 70% of the earth's surface. Add to this the fact that the deepest depressions go 11 thousand meters into the ocean depths and it becomes clear what spaces the fish own.

Life in water is extremely diverse, which could not but affect the appearance of fish, and led to the fact that the shape of their bodies is varied, like underwater life itself.

On the head of fish there are gill wings, lips and mouth, nostrils and eyes. The head transitions into the body very smoothly. Starting from the gill wings to the anal fin there is a body that ends with a tail.

Fins serve as organs of movement for fish. In essence, they are skin outgrowths that rest on bony fin rays. The most important thing for fish is the caudal fin. On the sides of the body, in its lower part, there are paired ventral and pectoral fins, which correspond to the hind and forelimbs of vertebrates living on the ground. In different species of fish, paired fins can be located differently. At the top of the fish’s body there is a dorsal fin, and at the bottom, next to the tail, there is an anal fin. Moreover, it is important to note that the number of anal and dorsal fins in fish can vary.

Most fish have an organ on the sides of their body that senses the flow of water, called the “lateral line.” Thanks to this, even a blind fish is able to catch moving prey without bumping into obstacles. The visible part of the lateral line consists of scales with holes.

Through these holes, water penetrates into a channel running along the body, where it is sensed by the endings of nerve cells passing through the channel. The lateral line in fish can be continuous, intermittent, or absent altogether.

Functions of fins in fish

Thanks to the presence of fins, fish are able to move and maintain balance in the water. If the fish is deprived of fins, it will simply turn over with its belly up, since the center of gravity of the fish is located in its dorsal part.

The dorsal and anal fins provide the fish with a stable body position, and the caudal fin in almost all fish is a kind of propulsion device.

As for the paired fins (pelvic and pectoral), they mainly perform a stabilizing function, since they provide an equilibrium body position when the fish is immobilized. With the help of these fins, the fish can take the body position it needs. In addition, they are load-bearing planes during the movement of the fish, and act as a rudder. As for the pectoral fins, they are a kind of small motor with which the fish moves during slow swimming. The pelvic fins are primarily used to maintain balance.

Body shape of fish

Fish are characterized by a streamlined body shape. This is a consequence of her lifestyle and habitat. For example, those fish that are adapted to long and fast swimming in the water column (for example, salmon, cod, herring, mackerel or tuna) have a body shape similar to a torpedo. Predators that practice lightning-fast throws over very short distances (for example, saury, garfish, taimen or) have an arrow-shaped body shape.

Some species of fish that are adapted to lying on the bottom for a long time, such as flounder or stingray, have a flat body. Some species of fish even have bizarre body shapes, which may resemble a chess knight, as can be seen in the horse, whose head is located perpendicular to the axis of the body.

The seahorse inhabits almost all sea waters on Earth. His body is encased in a shell like that of an insect, his tail is tenacious like that of a monkey, his eyes can rotate like those of a chameleon, and the picture is complemented by a bag similar to that of a kangaroo. And although this strange fish can swim, maintaining a vertical body position, using the vibrations of the dorsal fin to do this, it is still a useless swimmer. The seahorse uses its tubular snout as a “hunting pipette”: when prey appears nearby, the seahorse sharply inflates its cheeks and pulls the prey into its mouth from a distance of 3-4 centimeters.

The smallest fish is the Philippine goby Pandaku. Its length is about seven millimeters. It even happened that women of fashion wore this bull in their ears, using aquarium earrings made of crystal.

But the largest fish is the fish, whose body length is sometimes about fifteen meters.

Additional organs in fish

In some fish species, such as catfish or carp, antennae can be seen around the mouth. These organs perform a tactile function and are also used to determine the taste of food. Many deep-sea fish such as photoblepharon, anchovy, and hatchet fish have luminous organs.

On the scales of fish you can sometimes find protective spines, which can be located in different parts of the body. For example, the body of a hedgehog fish is almost completely covered with spines. Certain species of fish, such as the wart, sea dragon and, have special organs of attack and defense - poisonous glands, which are located at the base of the fin rays and the base of the spines.

Body coverings in fish

On the outside, the skin of fish is covered with thin translucent plates - scales. The ends of the scales overlap each other, arranged like tiles. On the one hand, this provides the animal with strong protection, and on the other hand, it does not interfere with free movement in the water. The scales are formed by special skin cells. The size of the scales can vary: in those they are almost microscopic, while in the Indian longhorned beetle they are several centimeters in diameter. Scales are distinguished by great diversity, both in their strength and in quantity, composition and a number of other characteristics.

The skin of fish contains chromatophores (pigment cells), when they expand, the pigment grains spread over a significant area, making the color of the body brighter. If the chromatophores are reduced, then the pigment grains will accumulate in the center and most of the cell will remain uncolored, due to which the body of the fish will become paler. When pigment grains of all colors are evenly distributed inside the chromatophores, the fish has a bright color, and if they are collected in the centers of the cells, the fish will be so colorless that it may even appear transparent.

If only yellow pigment grains are distributed among the chromatophores, the fish will change its color to light yellow. All the variety of colors of fish is determined by chromatophores. This is especially typical for tropical waters. In addition, the skin of fish contains organs that sense the chemical composition and temperature of the water.

From all of the above, it becomes clear that the skin of fish performs many functions at once, including external protection, protection from mechanical damage, communication with the external environment, communication with relatives, and facilitating gliding.

The role of color in fish

Pelagic fish often have a dark back and a light-colored belly, such as the abadejo fish, a member of the cod family. In many fish that live in the middle and upper layers of water, the color of the upper part of the body is much darker than the lower part. If you look at such fish from below, then its light belly will not stand out against the light background of the sky shining through the water column, which camouflages the fish from the sea predators lying in wait for it. In the same way, when viewed from above, its dark back merges with the dark background of the seabed, which protects not only from predatory sea animals, but also from various fishing birds.

If you analyze the coloration of fish, you will notice how it is used to imitate and camouflage other organisms. Thanks to this, the fish demonstrates danger or inedibility, and also gives signals to other fish. During the mating season, many species of fish tend to acquire very bright colors, while the rest of the time they try to blend in with their environment or imitate a completely different animal. Often this color camouflage is complemented by the shape of the fish.

Internal structure of fish

The musculoskeletal system of fish, like that of land animals, consists of muscles and a skeleton. The skeleton is based on the spine and skull, consisting of individual vertebrae. Each vertebra has a thickened part called the vertebral body, as well as lower and upper arches. Together, the upper arches form a canal in which the spinal cord is located, which is protected from injury by the arches. In the upper direction, long spinous processes extend from the arches. In the body part the lower arches are open. In the caudal part of the spine, the lower arches form a canal through which blood vessels pass. The ribs are adjacent to the lateral processes of the vertebrae and perform a number of functions, primarily protecting the internal organs and creating the necessary support for the muscles of the trunk. The most powerful muscles in fish are located in the tail and back.

The skeleton of a fish includes bones and bony rays of both paired and unpaired fins. In unpaired fins, the skeleton consists of many elongated bones attached to the thickness of the muscles. There is a single bone in the abdominal girdle. The free pelvic fin has a skeleton consisting of many long bones.

The skeleton of the head also includes a small skull. The bones of the skull serve as protection for the brain, but most of the skeleton of the head is occupied by the bones of the upper and lower jaws, the bones of the gill apparatus and the eye sockets. Speaking about the gill apparatus, we can primarily note the large gill covers. If you lift the gill covers slightly, then underneath you can see paired gill arches: left and right. Gills are located on these arches.

As for the muscles, there are few of them in the head; they are located mostly in the area of the gill covers, on the back of the head and jaws.

The muscles that provide movement are attached to the skeletal bones. The main part of the muscles is evenly located in the dorsal part of the animal’s body. The most developed are the muscles that move the tail.

The functions of the musculoskeletal system in the fish body are very diverse. The skeleton serves as protection for internal organs, bony fin rays protect the fish from rivals and predators, and the entire skeleton in combination with muscles allows this inhabitant of the waters to move and protect itself from collisions and impacts.

Digestive system in fish

The digestive system begins with a large mouth, which is located in front of the head and is armed with jaws. There are large small teeth. Behind the oral cavity is the pharyngeal cavity, in which you can see the gill slits, which are separated by interbranchial septa on which the gills are located. Outside, the gills are covered with gill covers. Next is the esophagus, followed by a fairly voluminous stomach. Behind it is the intestine.

The stomach and intestines, using the action of digestive juices, digest food, and gastric juice acts in the stomach, and in the intestine several juices are secreted by the glands of the intestinal walls, as well as the walls of the pancreas. Bile coming from the liver and gallbladder is also involved in this process. Water and food digested in the intestines are absorbed into the blood, and undigested remains are thrown out through the anus.

A special organ that is found only in bony fish is the swim bladder, which is located under the spine in the body cavity. The swim bladder arises during embryonic development as a dorsal outgrowth of the intestinal tube. In order for the bladder to be filled with air, the newly born fry floats to the surface of the water and swallows air into its esophagus. After some time, the connection between the esophagus and the swim bladder is interrupted.

It is interesting that some fish use their swim bladder as a means by which they amplify the sounds they make. True, some fish do not have a swim bladder. Usually these are those fish that live on the bottom, as well as those that are characterized by vertical rapid movements.

Thanks to the swim bladder, the fish does not sink under its own weight. This organ consists of one or two chambers and is filled with a mixture of gases, which in its composition is close to air. The volume of gases contained in the swim bladder can change when they are absorbed and released through the blood vessels of the swim bladder walls, as well as when air is swallowed. Thus, the specific gravity of the fish and the volume of its body can change in one direction or another. The swim bladder provides the fish with balance between its body mass and the buoyant force acting on it at a certain depth.

Gill apparatus in fish

As a skeletal support for the gill apparatus, fish serve four pairs of gill arches located in a vertical plane, to which the gill plates are attached. They consist of fringe-like gill filaments.

Inside the gill filaments there are blood vessels that branch into capillaries. Gas exchange occurs through the walls of the capillaries: oxygen is absorbed from the water and carbon dioxide is released back. Thanks to the contraction of the muscles of the pharynx, as well as due to the movements of the gill covers, water moves between the gill filaments, which have gill rakers that protect the delicate soft gills from clogging them with food particles.

Circulatory system in fish

Schematically, the circulatory system of fish can be depicted as a closed circle consisting of vessels. The main organ of this system is the two-chamber heart, consisting of an atrium and a ventricle, which ensures blood circulation throughout the animal’s body. Moving through the vessels, blood ensures gas exchange, as well as the transfer of nutrients in the body, and some other substances.

In fish, the circulatory system includes one circulation. The heart sends blood to the gills, where it is enriched with oxygen. This oxygenated blood is called arterial blood, and is carried throughout the body, distributing oxygen to the cells. At the same time, it is saturated with carbon dioxide (in other words, it becomes venous), after which the blood returns back to the heart. It should be recalled that in all vertebrates, the vessels leaving the heart are called arteries, while those returning to it are called veins.

The excretory organs in fish are responsible for removing metabolic end products from the body, filtering blood and removing water from the body. They are represented by paired kidneys, which are located along the spine by the ureters. Some fish have a bladder.

In the kidneys, excess fluid, harmful metabolic products and salts are extracted from the blood vessels. The ureters carry urine into the bladder, from where it is pumped out. Externally, the urinary canal opens with an opening located slightly behind the anus.

Through these organs, the fish removes excess salts, water and metabolic products harmful to the body.

Metabolism in fish

Metabolism is the totality of chemical processes occurring in the body. The basis of metabolism in any organism is the construction of organic substances and their breakdown. When complex organic substances enter the fish’s body along with food, during the process of digestion they are transformed into less complex ones, which, being absorbed into the blood, are carried throughout the cells of the body. There they form the proteins, carbohydrates and fats required by the body. Of course, this uses up the energy released during breathing. At the same time, many substances in cells break down into urea, carbon dioxide and water. Therefore, metabolism is a combination of the process of construction and breakdown of substances.

The intensity with which metabolism occurs in a fish’s body depends on its body temperature. Since fish are animals with variable body temperatures, that is, cold-blooded, their body temperature is in close proximity to the ambient temperature. As a rule, the body temperature of fish does not exceed the ambient temperature by more than one degree. True, in some fish, for example tuna, the difference can be about ten degrees.

Nervous system of fish

The nervous system is responsible for the coherence of all organs and systems of the body. It also ensures the body’s response to certain changes in the environment. It consists of the central nervous system (spinal cord and brain) and the peripheral nervous system (branches extending from the brain and spinal cord). The fish brain consists of five sections: the anterior, which includes the optic lobes, the middle, intermediate, cerebellum and medulla oblongata. All pelagic fish leading an active lifestyle have a fairly large cerebellum and optic lobes, since they need fine coordination and good vision. The medulla oblongata in fish passes into the spinal cord, ending in the caudal spine.

With the help of the nervous system, the fish’s body responds to irritations. These reactions are called reflexes, which can be divided into conditioned and unconditioned reflexes. The latter are also called innate reflexes. Unconditioned reflexes manifest themselves in the same way in all animals belonging to the same species, while conditioned reflexes are individual and are developed during the life of a particular fish.

Sense organs in fish

The sense organs of fish are very well developed. The eyes are able to clearly recognize objects at close range and distinguish colors. Fish perceive sounds through the inner ear located inside the skull, and smells are recognized through the nostrils. In the oral cavity, the skin of the lips and antennae, there are taste organs that allow fish to distinguish between salty, sour and sweet. The lateral line, thanks to the sensitive cells located in it, reacts sensitively to changes in water pressure and transmits corresponding signals to the brain.

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Habitats and external structure of fish

The habitat of fish is various bodies of water on our planet: oceans, seas, rivers, lakes, ponds. It is very vast: the area occupied by the oceans exceeds 70% of the Earth’s surface, and the deepest depressions go 11 thousand meters deep into the oceans.

The variety of living conditions in water influenced the appearance of fish and contributed to a wide variety of body shapes: the emergence of many adaptations to living conditions, both in structure and in biological characteristics.

General plan of the external structure of fish

On the head of the fish there are eyes, nostrils, a mouth with lips, and gill covers. The head smoothly transitions into the body. The body continues from the gill covers to the anal fin. The body of the fish ends with a tail.

The outside of the body is covered with skin. Protects mucus-coated skin of most fish scales .

The locomotion organs of fish are fins . Fins are outgrowths of skin resting on bones. fin rays . The caudal fin is of greatest importance. On the lower sides of the body there are paired fins: pectoral and ventral. They correspond to the fore and hind limbs of terrestrial vertebrates. The position of paired fins varies among different fish. The dorsal fin is located on top of the fish’s body, and the anal fin is located below, closer to the tail. The number of dorsal and anal fins may vary.

On the sides of the body of most fish there is a kind of organ that senses the flow of water. This lateral line . Thanks to the lateral line, even blinded fish do not bump into obstacles and are able to catch moving prey. The visible part of the lateral line is formed by scales with holes. Through them, water penetrates into a channel stretching along the body, to which the endings of nerve cells approach. The lateral line may be intermittent, continuous, or completely absent.

Functions of fins

Thanks to fins, fish are able to move and maintain balance in the aquatic environment. Deprived of fins, it turns over with its belly up, since the center of gravity is located in the dorsal part.

Unpaired fins (dorsal and anal) provide stability to the body. The caudal fin in the vast majority of fish performs the function of propulsion.

Paired fins (thoracic and abdominal) serve as stabilizers, i.e. provide a balanced position of the body when it is immobile. With their help, the fish maintains its body in the desired position. When moving, they serve as load-bearing planes and steering wheels. The pectoral fins move the fish's body when swimming slowly. The pelvic fins perform mainly a balancing function.

Fish have a streamlined body shape. It reflects the characteristics of the environment and lifestyle. In fish adapted to fast, long-term swimming in the water column ( tuna(2), mackerel, herring, cod, salmon ), “torpedo-shaped” body shape. In predators that practice quick throws at short distances ( pike, taimen, barracuda, garfish (1) , saury), it is “arrow-shaped”. Some fish adapted to long-term residence on the bottom ( stingray (6) , flounder (3) ), have a flat body. In some species, the body has a bizarre shape. For example, sea Horse resembles a corresponding chess piece: its head is located at right angles to the axis of the body.

Sea Horses inhabit different oceans of the globe. These fish surprise everyone who observes them: the body, like an insect, is enclosed in a shell, the prehensile tail of a monkey, the rotating eyes of a chameleon and, finally, a pouch like a kangaroo.

Although this cute fish can swim upright using the oscillatory movement of its dorsal fin, it is a poor swimmer and spends most of its time hanging, clinging to the seaweed with its tail and looking for small prey. The tubular snout of the skate acts like a pipette - when the cheeks are sharply inflated, the prey is quickly drawn into the mouth from a distance of up to 4 cm.

The smallest fish is considered Philippine bull Pandaku . Its length is about 7 mm. At one time fashionistas wore these fish in their ears. In crystal aquarium earrings!

The biggest fish is considered whale shark, which reaches a length of 15 m.

Additional fish organs

Some fish species (such as carp and catfish) have antennae around their mouths. These are additional organs of touch and determination of the taste of food. In many deep-sea fish (for example, deep-sea anglerfish, hatchet fish, anchovy, photoblepharon ) luminous organs are developed.

There are protective spines on the scales of fish. They can be located in different parts of the body. For example, spines cover the body hedgehog fish .

Some fish, for example scorpionfish, sea dragon, wart They have organs of defense and attack - poisonous glands located at the base of the spines and fin rays.

Coverings of the body

On the outside, the skin of fish is covered with scales - thin translucent plates. The scales overlap each other with their ends, arranged in a tile-like manner. This provides

strong protection of the body and at the same time does not create obstacles to movement. Scales are formed by special skin cells. The size of the scales varies: from microscopic to blackheads up to several centimeters Indian barbel . There is a wide variety of scales: in shape, strength, composition, quantity and some other characteristics.

Lie in the skin pigment cells - chromatophores : when they expand, the pigment grains spread over a larger space and the color of the body becomes bright. If the chromatophores contract, the pigment grains accumulate in the center, leaving most of the cell uncolored, and the body color fades. If pigment grains of all colors are evenly distributed inside the chromatophores, the fish is brightly colored; if pigment grains are collected in the centers of cells, the fish becomes almost colorless and transparent; if only yellow pigment grains are distributed among their chromatophores, the fish changes color to light yellow.

Chromatophores determine the diversity of fish colors, which are especially bright in the tropics. Thus, fish skin performs the function of external protection. It protects the body from mechanical damage, facilitates sliding, determines the color of the fish, and communicates with the external environment. The skin contains organs that sense the temperature and chemical composition of water.

Color meaning

Pelagic fish often have a dark "back" and a light "belly" like this fish abadejo cod family.

Indian glass catfish can serve as a textbook for studying anatomy.

Many fish that live in the upper and middle layers of water have a darker color on the upper part of the body and a lighter color on the lower part. The silvery belly of the fish, if you look at the fish from below, will not stand out against the light background of the sky. In the same way, the dark back, if you look at the fish from above, will merge with the dark background of the bottom.

By studying the coloration of fish, you can see how it helps camouflage and imitate other species of organisms, observe the demonstration of danger and inedibility, as well as the presentation of other signals by fish.

During certain periods of life, many fish acquire bright mating colors. Often the color and shape of the fish complement each other.

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The hydrosphere is characterized by an extreme diversity of conditions. These are fresh, flowing and stagnant waters, as well as salty seas and oceans, inhabited by organisms at different depths. To exist in such diverse conditions, fish have developed both general principles of structure that meet the requirements of the environment (smooth, elongated body without protrusions, covered with mucus and scales; pointed head with pressed gill covers; fin system; lateral line), and adaptations characteristic of individual groups (flattened body, light organs, etc.). Each species of fish has numerous and varied adaptations corresponding to a specific way of life.

The unpaired fins include the dorsal, anal and caudal fins.

The dorsal and anal fins act as stabilizers and resist lateral displacement of the body during tail action.

The large dorsal fin of sailfish acts as a rudder during sharp turns, greatly increasing the maneuverability of the fish when pursuing prey. The dorsal and anal fins of some fish act as propellers, imparting forward movement to the fish (Fig. 15).

Figure 15 – Shape of undulating fins in various fish:

1 - sea Horse; 2 – sunflower; 3 – moon fish; 4 – body; 5 – needlefish; 6 – flounder; 7 - electric eel.

Locomotion with the help of undulating movements of the fins is based on the wave-like movements of the fin plate, caused by successive transverse deflections of the rays. This method of movement is usually characteristic of fish with a short body length that are unable to bend the body - boxfishes, sunfish. Only due to the undulation of the dorsal fin do seahorses and pipefish move. Fishes such as flounders and sunfishes, along with the undulating movements of the dorsal and anal fins, swim by laterally curving their body.

Figure 16 – Topography of the passive locomotor function of unpaired fins in various fish:

1 – eel; 2 – cod; 3 – horse mackerel; 4 – tuna.

In slow-swimming fish with an eel-like body shape, the dorsal and anal fins, merging with the caudal fin, form in a functional sense a single fin bordering the body and have a passive locomotor function, since the main work falls on the body body. In fast-moving fish, as the speed of movement increases, the locomotor function is concentrated in the posterior part of the body and on the posterior parts of the dorsal and anal fins. An increase in speed leads to the loss of locomotor function by the dorsal and anal fins, reduction of their posterior sections, while the anterior sections perform functions not related to locomotion (Fig. 16).

In fast-swimming scombroid fish, the dorsal fin fits into a groove running along the back when moving.

Herring, garfish and other fish have one dorsal fin. Highly organized orders of bony fish (perciformes, mullets) usually have two dorsal fins. The first consists of spiny rays, which give it a certain lateral stability. These fish are called spiny-finned fish. Gadfish have three dorsal fins. Most fish have only one anal fin, but cod-like fish have two.

Some fish lack dorsal and anal fins. For example, the electric eel does not have a dorsal fin, the locomotor undulating apparatus of which is the highly developed anal fin; Stingrays do not have it either. Stingrays and sharks of the order Squaliformes do not have an anal fin.

Figure 17 – Modified first dorsal fin of the sticky fish ( 1 ) and anglerfish ( 2 ).

The dorsal fin can be modified (Fig. 17). Thus, in the sticky fish, the first dorsal fin moved to the head and turned into a suction disk. It is, as it were, divided by partitions into a number of independently acting smaller, and therefore relatively more powerful, suction cups. The septa are homologous to the rays of the first dorsal fin; they can bend back, taking an almost horizontal position, or straighten. Due to their movement, a suction effect is created. In anglerfish, the first rays of the first dorsal fin, separated from each other, turned into a fishing rod (ilicium). In sticklebacks, the dorsal fin has the appearance of separate spines that perform a protective function. In triggerfish of the genus Balistes, the first ray of the dorsal fin has a locking system. It straightens and is fixed motionless. You can remove it from this position by pressing the third spiny ray of the dorsal fin. With the help of this ray and the spiny rays of the ventral fins, the fish, when in danger, hides in crevices, fixing the body in the floor and ceiling of the shelter.

In some sharks, the rear elongated lobes of the dorsal fins create a certain lifting force. A similar, but more significant, supporting force is created by the anal fin with a long base, for example, in catfishes.

The caudal fin acts as the main mover, especially with the scombroid type of movement, being the force that imparts forward movement to the fish. It provides high maneuverability of fish when turning. There are several forms of the caudal fin (Fig. 18).

Figure 18 – Shapes of the caudal fin:

1 – protocentral; 2 – heterocercal; 3 – homocercal; 4 – diphycercal.

Protocercal, i.e., primarily equilobed, has the appearance of a border, and is supported by thin cartilaginous rays. The end of the chord enters the central part and divides the fin into two equal halves. This is the most ancient type of fin, characteristic of cyclostomes and larval stages of fish.

Diphycercal – symmetrical externally and internally. The spine is located in the middle of equal blades. It is characteristic of some lungfishes and lobe-finned fishes. Of the bony fishes, garfish and cod have such a fin.

Heterocercal, or asymmetrical, unequally lobed. The upper blade expands, and the end of the spine, bending, enters it. This type of fin is characteristic of many cartilaginous fishes and cartilaginous ganoids.

Homocercal, or falsely symmetrical. This fin can be externally classified as equilobed, but the axial skeleton is distributed unequally in the blades: the last vertebra (urostyle) extends into the upper blade. This type of fin is widespread and characteristic of most bony fish.

According to the ratio of the sizes of the upper and lower blades, the caudal fins can be epi-, hypo- And isobathic(ecclesiastical). With the epibate (epicercal) type, the upper lobe is longer (sharks, sturgeons); with hypobate (hypocercal) the upper lobe is shorter (flying fish, sabrefish), with isobathic (isocercal) both lobes have the same length (herring, tuna) (Fig. 19). The division of the caudal fin into two blades is associated with the peculiarities of counter currents of water flowing around the body of the fish. It is known that a friction layer is formed around a moving fish - a layer of water, to which a certain additional speed is imparted by the moving body. As the fish develops speed, the boundary layer of water may separate from the surface of the fish's body and a zone of vortices may form. If the body of the fish is symmetrical (relative to its longitudinal axis), the zone of vortices that arises behind is more or less symmetrical relative to this axis. In this case, to exit the zone of vortices and the friction layer, the blades of the caudal fin lengthen equally - isobathism, isocercia (see Fig. 19, a). With an asymmetrical body: a convex back and a flattened ventral side (sharks, sturgeons), the vortex zone and the friction layer are shifted upward relative to the longitudinal axis of the body, therefore the upper lobe elongates to a greater extent - epibathicity, epicercia (see Fig. 19, b). If fish have a more convex ventral and straight dorsal surface (siberian fish), the lower lobe of the caudal fin lengthens, since the vortex zone and the friction layer are more developed on the lower side of the body - hypobate, hypocercion (see Fig. 19, c). The higher the speed of movement, the more intense the process of vortex formation and the thicker the friction layer and the more developed the blades of the caudal fin, the ends of which must extend beyond the zone of vortices and the friction layer, which ensures high speeds. In fast-swimming fish, the caudal fin has either a semilunar shape - short with well-developed sickle-shaped elongated blades (scombroids), or forked - the notch of the tail goes almost to the base of the fish's body (horse mackerel, herring). In sedentary fish, during the slow movement of which the processes of vortex formation almost do not take place, the blades of the caudal fin are usually short - a notched caudal fin (carp, perch) or not differentiated at all - rounded (burbot), truncated (sunfish, butterfly fish), pointed ( captain's croakers).

Figure 19 – Layout of the caudal fin blades relative to the vortex zone and friction layer for different body shapes:

A– with a symmetrical profile (isocercia); b– with a more convex profile contour (epicerkia); V– with a more convex lower contour of the profile (hypocercia). The vortex zone and friction layer are shaded.

The size of the caudal fin blades is usually related to the body height of the fish. The higher the body, the longer the caudal fin blades.

In addition to the main fins, fish may have additional fins on their body. These include fatty fin (pinna adiposa), located behind the dorsal fin above the anal fin and representing a fold of skin without rays. It is typical for fish of the Salmon, Smelt, Grayling, Characin and some catfish families. On the caudal peduncle of a number of fast-swimming fish, behind the dorsal and anal fins, there are often small fins consisting of several rays.

Figure 20 – Keels on the caudal peduncle of fish:

A– in the herring shark; b- in mackerel.

They act as dampers for turbulence generated during the movement of fish, which helps to increase the speed of fish (scombroid, mackerel). On the caudal fin of herrings and sardines there are elongated scales (alae), which act as fairings. On the sides of the caudal peduncle in sharks, horse mackerel, mackerel, and swordfish there are lateral keels, which help reduce the lateral bendability of the caudal peduncle, which improves the locomotor function of the caudal fin. In addition, the side keels serve as horizontal stabilizers and reduce vortex formation when the fish swims (Fig. 20).

Pisces use many different methods to communicate. Of course, not as much as humans or other higher vertebrates. To communicate certain information to surrounding fish or other animals, fish can use chemical, electrolocation, sound and, as it turned out, visual methods, that is, they use “sign language” for communication. And although fishermen, unlike aquarists, divers or underwater hunters, are less likely to look a live fish in the eyes, some basic fish language can be learned.

Familiarization
The visible signals that fish can give to fish or other animals around them can be divided into several main groups. The first group is spawning postures or even gestures and facial expressions. After all, the movements of the fins can be called gestures, and the slightly open and even curved mouth can be called facial expressions.

The second group of visual signals demonstrates aggression, attack, and they indicate that this individual is “on the warpath.” There is also a large group of defensive gestures. This is not open aggression, but such gestures clearly show that we are peaceful fish, but “our armored train is on a siding.” Fish demonstrate these gestures more often than others.

The same group of gestures applies to protecting the territory, and to protecting one’s found (caught) food object, and to protecting the cubs.

Another important visual stimulus is the color of the fish. In a sufficient number of fish species, under stress, during spawning, during an aggressive attack or defense of their “good,” a color change occurs, which signals something out of the ordinary. Something similar happens to a person when, out of anger, shame or tension, he blushes and thereby betrays himself.

Unfortunately, the sign language of fish has not yet been fully studied and is by no means for all species, but still, knowledge of the general principles of gestural communication of fish will help to understand fish. By the way, scientists suggest that fish of each species have a personal sign language, which is understood very well by closely related species and much worse by species that are far apart in their position in the taxonomy.

Gestures of aggression and defense
These gestures may, of course, vary among fish of different species, but they have much in common and are understandable to other fish. The greatest researcher of animal behavior, Nobel Prize laureate Konrad Lorenz said: “Aggression is one of the most important factors in maintaining the structure of communities of most animal groups.”

Lorenz pointed out that the existence of groups with close individual connections between individuals is possible only in animals with a sufficiently developed ability for directed aggression, in which the union of two or more individuals contributes to better survival.

In fish, the key aggressive gesture can be considered this: one of the fish turns to the other and begins to open its mouth wide (this is how dogs, wolves and other land animals grin). This gesture can be deciphered as a gesture of a frontal threat (attack).

So if a shark grins at you, leave quickly. While the mouth is just opening, this is some kind of beginning of a threat, territorial defense or any defensive gesture.

An important key point not only of this aggressive gesture, but also of other gestures of the same group: a fish with an open mouth seems larger, and therefore scarier and more impressive. At the same time, her attack looks more convincing and effective.

By the way, spreading the pectoral fins to the sides, protruding gill covers, and inflating the body with various tetraodons also leads to a general increase in the body volume of the frightening fish.

Male fish use certain poses of aggression and active defense to conquer females before spawning. There is no talk of direct use of gestures at this moment, but the female sees how big and serious the suitor is in front of her.

These “exaggeration” poses are very important for fish. After all, they grow throughout their lives, and for them size plays a primary role. Adult individuals, already showing aggressive behavior with all their might, are often large in size.

And the one who is larger is stronger, and older, and more experienced, and more important. That is, he has the right to food, territory, and the best female. Therefore, fish often try to visually exaggerate their size.

An exaggeration of size that frightens the enemy is also achieved by occupying a higher point in space. It is enough to force your opponent to look up, and he will feel inferior to you. Demonstration of the sides of the body and fluttering of the caudal fin and the entire body is often a manifestation of spawning behavior, that is, spawning gestures, or releasers.

However, in some fish (for example, ruffes and other perches), such a display of the sides and trembling of the tail is a typical aggressive gesture. This gesture of some fish is called a “side threat”. Unlike the “frontal threat”, it does not look so intimidating.

The spreading of the fins, often accompanied by trembling (or fluttering, or even shaking of the body), can be interpreted, depending on the situation, as aggression, as active defense, and as gestures of spawning behavior.

And in many territorial fish, such lateral displays, which are accompanied by vibrations of the body and spreading of the fins, have a dual function. For fish of the same species, but of the opposite sex, this is an attractive maneuver, showing what a beautiful, large and wonderful partner is swimming nearby.

And for relatives of the same sex, these gestures mean one thing: this is my female and my place, and you can leave! If one male (or female) spreads his fins, and his opponent, on the contrary, folds them, this means the latter’s complete surrender.

When the enemy in response inflates his fins and vibrates his body, this means that he is accepting the battle and there will be a show. A very important evolutionary point is the demonstration of aggression instead of a direct attack. Indeed, in its original form, aggression involves attacking an object, causing physical damage to it, or even killing it.

In the process of animal evolution, an aggressive attack was replaced by a demonstration of the threat of the possibility of an attack, especially during clashes between individuals of the same species. A demonstration, by causing fear in the enemy, allows you to win a skirmish without resorting to a fight, which is very dangerous for both sides.

Physical confrontation is replaced by psychological confrontation. Therefore, developed aggressive behavior, including many threats and frightening actions, is useful for the species, and for well-armed species it is simply life-saving.

This is why Lorenz argued that well-formed aggressive behavior is one of the remarkable achievements of natural selection and is essentially humane.

In fish, one of the main weapons of demonstration (instead of attack) is spines in the fins, spiny gill covers or plaques on the body. That is, the easiest way to scare an enemy is by showing him the means of defense and attack that this type of animal has.

Therefore, the fish, threatening, spread their fins and raise their spines; many stand upright in the water, exposing them to the enemy.

The fight process in fish consists of five to six successive phases:

warning with taking the appropriate posture;
excitement of opponents, usually accompanied by a change in color;
bringing fish closer together and demonstrating a threat pose;
mutual blows with the tail and mouth;
retreat and defeat of one of the opponents.

There are also phases of breaks to relieve tension and to rest during the battle or demonstration of strength.

Coloring and body pattern like spawning releasers
There are a lot of such visual and identification signals. During spawning, when the fish has a special hormonal background, many species change color and pattern - this is a signal that it is ready to reproduce.

For reliability, chemical and other signals also work actively, so that the fish is not mistaken and the species continues to exist. In addition to spawning, coloring and pattern help fish during schooling: often stripes on the body serve as a visual stimulus, helping thousands of fish stay close and correctly positioned relative to each other.

Coloring makes it possible to recognize your relative or, conversely, an enemy and dangerous individual. Many fish, especially those in which visual signals play an important role (pike, perch, pike perch and others), remember well the external features of “their” and “alien” fish. Often two or three “lessons” are enough for the fish to remember well the color and pattern of the hostile fish.

Sometimes not only the color of the entire body, but also the color of individual fins (for example, abdominal or pectoral), or individual brightly colored areas on the body (abdomen, back, head) signal to potential partners that “ready to spawn!”

A spot on the abdomen of many females indicates that there is a lot of caviar in the abdomen, it is enlarged and bright. However, in most cases, bright coloring is destructive outside of spawning: it unmasks peaceful fish from predators, and, on the contrary, reveals a predator ahead of time.

So most of the fish in our reservoirs during the normal non-spawning period have a gray, inconspicuous appearance, and developed gesticulation is all the more important for them.
In addition to spawning behavior or identification of “friend” or “alien,” coloration can work as a factor determining status.

The brighter the color and clearer the pattern, the higher the social status of this individual. This is not always the case, but it is often the case. Fish can use their coloration to demonstrate threat (strong, intense coloration) or submission (less bright or dull coloration), usually this is supported by appropriate gestures that reinforce the information. Bright coloring is actively used by fish that protect their offspring, raise young and drive away other fish that are dangerous to the young. It also helps juveniles identify their parents and notice them among other fish.

In parental behavior, fish have a highly developed not only body color language, but also body language. The young quickly remember that the flapping of the pelvic fins and the pressed pectoral fins mean the call “swim to mom”; a bend of the body and a slightly open mouth - “swim after me”; fins spread out are a command to hide in cover.

For normal relationships between parents and young, it is necessary to suppress certain reactions. Very interesting examples of this have been observed in fish. Some chromis (family Cichlids) carry young fish in their mouths; At this time, adult fish do not feed at all.

A funny case is described with a male of one species of chromis, whose representatives every evening transfer the young to the “bedroom” - a hole dug in the sand. This “father” was collecting fry in his mouth, grabbing the ones that had strayed to the side one by one, and suddenly he saw a worm: after hesitating a little, he finally spat out the fry, grabbed and swallowed the worm, and then again began to collect the “cubs” to transfer them to the hole .

A straightened, erect dorsal fin indicates both the onset of aggressive behavior (for example, when protecting one's territory) and an invitation to spawn.

Rituals and demonstrations
To understand the sign language of fish, you need to know their rituals and the meaning of different poses and gestures, which say a lot about the fish’s intentions. Rituals and demonstrative acts of behavior exhibited by animals in conflict situations can be divided into two groups: rituals of threat and rituals of pacification, inhibiting aggression from stronger relatives. Lorenz identified several main features of such rituals.

Demonstrative exposure of the most vulnerable part of the body. It is very interesting that dominant animals often demonstrate this behavior. So, when two wolves or dogs meet, the stronger animal turns its head away and exposes to its opponent the area of the carotid artery, curved towards the bite.

The meaning of such a demonstration is that the dominant signals in this way: “I’m not afraid of you!” This is more likely to apply to more highly developed animals, but some fish also exhibit similar behavior. For example, cichlids show folded fins and caudal peduncle to a strong enemy.

Fish have organs that can be called organs of ritual behavior. These are fins and gill covers. Ritual ones are modified fins, which in the process of evolution turn into thorns or spines or, conversely, into veil formations. All these “decorations” are clearly demonstrated in front of other individuals of their species, in front of a female or a rival. Coloring can also be ritualistic.

For example, tropical fish have a false “eye” - a bright spot in the upper corner of the dorsal fin that imitates the eye of a fish. The fish exposes this corner of the fin to the enemy, the enemy grabs onto it, thinking that it is an eye and that he will now kill the victim.

And he just rips out several rays of the dorsal fin with this bright spot, and the victim swims away safely almost unharmed. Obviously, in the course of evolution, both the decorations themselves and the ways of displaying them developed in parallel.

The demonstration of signal structures carries vital information that indicates to other individuals the gender of the demonstrating animal, its age, strength, ownership of a given area of the area, etc.

Ritual demonstrations of territorial behavior among fish are very important and interesting. The forms of aggressive territorial behavior themselves are far from being limited to direct attacks, fights, chases, etc. One can even say that such “harsh” forms of aggression, associated with inflicting wounds and other damage to the enemy, are not such a common phenomenon in the general system of individualization of territory.

Direct aggression is almost always accompanied by special “ritual” forms of behavior, and sometimes the protection of an area is completely limited to them. And the clashes themselves on territorial grounds are relatively rarely accompanied by causing serious damage to the enemy. Thus, frequent fights of goby fish at the boundaries of areas are usually very short-lived and end with the flight of the “intruder”, after which the “owner” begins to swim vigorously in the reclaimed area.

Fish actively mark their territory. Each species does this in its own way, depending on which sensory systems prevail in a given species. Thus, the territory is visually marked by species that live in small, easily visible areas. For example, the same coral fish. A clear, bright, unusual and different from other fish body pattern (and coloring) - all this in itself indicates that the owner of the population of this species is located in this area.

Hierarchy and poses of fish with gestures
The first meeting of animals rarely occurs without some tension, without mutual manifestation of aggressiveness. A fight breaks out, or the individuals demonstrate their unfriendliness with decisive gestures and threatening sounds. However, after the relationship is cleared up, fights rarely occur. When meeting again, animals unquestioningly give way to a stronger opponent the road, food or other object of competition.

The order of subordination of animals in a group is called hierarchy. Such orderliness of relationships leads to a reduction in energy and mental costs that arise from constant competition and clarification of relationships. Animals at the lower levels of the hierarchy, subject to aggression from other members of the group, feel oppressed, which also causes important physiological changes in their body, in particular the occurrence of an increased stress response. It is these individuals that most often become victims of natural selection.

Each individual is either superior in strength to its partner or inferior to it. Such a hierarchical system is formed when fish collide in the struggle for a place in a reservoir, for food and for a female.

The fish just opened its mouth and raised its fin, and its size visually increased by almost 25%. This is one of the most accessible and common ways to raise your authority in the animal world.

In the early stages of establishing a hierarchy, a lot of fights occur between fish (which are inherently hierarchical in principle). After the final establishment of the hierarchy, aggressive collisions between fish individuals practically cease, and the order of subordination of individuals is maintained in the population.

Usually, when a high-ranking fish approaches, subordinate individuals yield to it without resistance. In fish, size is most often the main criterion for dominance in the hierarchical ladder.
The number of collisions in a group of animals increases sharply when there is a lack of food, space or other living conditions. Lack of food, causing more frequent collisions of fish in a school, causes them to spread out somewhat to the sides and take over additional feeding area.

Fatal fights between very aggressive fish species in fish farms and aquariums are observed much more often than in natural conditions. This can easily be explained by stress and the inability to separate opponents. A kind of eternal ring. Therefore, aquarists know how important it is to provide plenty of hiding places in a pond if the fish are territorial. It’s even safer to keep them separate.

The lower links of the fish in the hierarchical ladder should demonstrate postures of subordination, humility and appeasement. What does a losing fish do? First of all, she raises the “white flag”, that is, folds her fins, removes thorns, thorns and teeth (sharks). These attributes of aggressiveness are removed until better times, that is, before meeting an even weaker opponent.

The size of individuals decreases before our eyes. As far as possible, of course. That is, the losing outsider fish demonstrates to the enemy: “I’m small and unarmed, I’m not afraid of you!” And the strong, victorious opponent also understands that he no longer needs to demonstrate his strength, and closes his mouth, assumes a horizontal position, folds his fins, removes thorns and thorns (if there are any, of course).

Sometimes a defeated fish turns over with its belly up and this also demonstrates its defenselessness. I deliberately do not present data on specific species here, since there are very few of them, and many have not yet been statistically confirmed.

I hope that interesting information will help anglers better understand fish, and not once again frighten or cause harm to either a specific fish or a school or population as a whole.

Source: Ekaterina Nikolaeva, Fish with us 3/2013 159

Gustera

Silver bream fish. The silver bream differs from the above-described species of bream solely in the number and location of the pharyngeal teeth, of which there are not five, but seven on each side, and moreover, in two rows. In body shape it is very similar to a young bream, or rather, a bream, but has a smaller number of rays in the dorsal (3 simple and 8 branched) and anal (3 simple and 20-24 branched) fins; in addition, its scales are noticeably larger, and its paired fins are reddish in color.

The body of the silver bream is strongly flattened, and its height is at least a third of its entire length; her nose is blunt, her eyes are large and silvery; the back is bluish-gray, the sides of the body are bluish-silver; unpaired fins are gray, and paired fins are red or reddish at the base, dark gray towards the apex. However, this fish, depending on age, time of year and local conditions, presents significant modifications.

Gustera never reaches a significant size. For the most part it is no more than one pound and less than a foot in length; One and a half and two pound ones are less common, and only in a few places, for example in the Gulf of Finland. Lake Ladoga, it weighs up to three pounds. This fish has a much wider distribution than syrty, bluefish and glazach.

Gustera is found in almost all European countries: France, England, Sweden, Norway, throughout Germany, Switzerland, and it seems to be absent only in Southern Europe. In all the above-mentioned areas, it belongs to very common fish. In Russia, the silver bream is found in all rivers, sometimes even small rivers, also in lakes, especially in the northwestern provinces, and flowing ponds; in Finland it reaches 62° N. sh.; It is also found in the northern parts of Lake Onega, and in northern Russia it goes even further - to Arkhangelsk.

It seems that it no longer exists in Pechora, and in Siberia it was found only recently (Varpakhovsky) in the river. Iset, a tributary of the Tobol. There is no silver bream in the Turkestan region, but in Transcaucasia it has so far been found at the mouth of the Kura River and in Lake. Paleostome, off the coast of the Black Sea. Silver bream is a sluggish, lazy fish and, like bream, loves quiet, deep, fairly warm water, with a silty or clayey bottom, which is why it is very often found with this latter.

It lives in one place for a long time and most willingly stays near the very shores (hence its French name - la Bordeliere and Russian berezhnik), especially in the wind, since the shafts, eroding the banks, and in shallow places the very bottom, reveal various worms and larvae. It apparently lives in small numbers at the mouths of rivers and at the seaside itself, such as, for example, at the mouths of the Volga and in the Gulf of Finland between St. Petersburg and Kronstadt.

In spring and autumn, the silver bream is found in extremely dense flocks, which, of course, is where its common name comes from. However, it rarely makes very long journeys and almost never reaches, for example, the middle reaches of the Volga, where its own local bream lives. In general, the main mass of these fish accumulate in the lower reaches of rivers, in the sea, and, like very many others, they make regular periodic movements: in the spring they go up for spawning, in the fall for wintering.

Entering wintering grounds in the fall, they lie down in pits under the riffles in such large masses that in the lower reaches of the Volga it happens that up to 30 thousand of them can be pulled out in one ton. The food of the silver bream is almost the same as that of other types of bream: it feeds exclusively on mud and small mollusks, crustaceans and worms contained in it, most often bloodworms, but it also destroys the eggs of other fish, especially (according to Bloch’s observations) rudd caviar.

Spawning of the silver bream begins very late, b. hours after the end of bream spawning - at the end of May or at the beginning of June, in the south a little earlier. At this time, its scales change color, and the paired fins acquire a brighter red color; in males, in addition, small granular tubercles develop on the gill covers and along the edges of the scales, which then disappear again. Usually, small silver bream spawns earlier, large ones later.

In the Gulf of Finland, other fishermen distinguish two breeds of silver bream: one breed, according to them, is smaller, lighter in color, spawns earlier and is called Trinity (based on the time of spawning), and the other breed is much larger (up to 3 pounds), darker in color, spawns later and is called Ivanovskaya. According to Bloch’s observations, in Germany the largest silver bream spawns first, followed by the smallest one a week or nine days later.

The silver bream chooses grassy and shallow bays as a spawning site and spawns eggs extremely noisily, like bream, but incomparably quieter than it: at this time it sometimes even happens to catch them with your hands; then they catch her in the muzzle, winged and nonsense by the pounds. It usually spawns from sunset to ten o'clock in the morning, and each age finishes the game at 3-4 at night, but if cold weather interferes, then in one day.

In a medium-sized female, Bloch counted more than 100 thousand eggs. According to Sieboldt, the silver bream becomes capable of reproduction very early, not yet reaching 5 inches in length, so we must assume that it spawns in its second year. The main catch of silver bream is carried out in the spring - with seines, but in the lower reaches of rivers, especially on the Volga, even greater catches of this fish occur in the fall. The most complete information about crucian fish is here.

Silver bream generally belongs to low-value fish and is rarely prepared for future use, unless it is caught in very large quantities. Salted and dried silver bream on the lower Volga is sold under the name tarani; in the rest of the Volga region she b. h. is sold fresh and has only local sales. However, it is very suitable for fish soup and is held in rather greater esteem in the Volga provinces, where there is a saying about it: “Large silver bream is tastier than small bream.”

Where there is a lot of silver bream, it takes the bait very well, especially after spawning. In some places they usually fish for silver bream with a worm, from the bottom, like bream, and its bite is similar to the latter’s bite; The silver bream, even more often than the bream, drags the float to the side without submerging it, and often hooks itself. This is perhaps the most daring and annoying fish, which is pure punishment for anglers fishing with bait.

It has been noticed that she takes best at night. According to Pospelov, the silver bream on the river. Teze (in Vladimir province) is caught as if with pieces of salted herring. In Germany in the fall it also goes well for bread with honey, and on the Volga it is very often caught in winter from ice holes (using a worm). The winter bite of the silver bream has the usual character - it first twitches, then slightly drowns. For catching catfish, pike and large perches, the silver bream is one of the best baits, as it is much more durable than other types of bream.

In many places in Russia, for example. in the Dnieper, Dniester, on the middle and lower Volga, occasionally - usually alone and in schools of other fish, b. including silver bream and roach (roach) - there is one fish that occupies, as it were, the middle between bream, silver bream and roach (Abramidopsis), on the river. In Mologa this fish is called ryapusa, in Nizhny Novgorod, Kazan and on the Dnieper - all fish, all fish, on the grounds that it resembles different carp fish: blue bream, silver bream, roach, rudd.

According to fishermen, as well as some scientists, this is a bastard from bream and roach or silver bream and roach. In Kazan, one fisherman even claimed to prof. Kessler that all fish hatch from roach eggs fertilized by male silver bream. In terms of body shape and pharyngeal teeth, this cross is still closer to the genus Abramis.

The height of its body is about 2/7 of the entire length, the mouth occupies the top of the snout and the lower jaw is slightly turned upward; the scales are larger than those of other breams, and the anal fin contains only 15-18 unbranched rays; the lower lobe of the caudal fin is barely longer than the upper one, before Abramidopsis is already approaching the roach. It would be more correct to assume that this is mostly a cross between bream and roach.

A similar cross is Bliccopsis abramo-rutilus Holandre, which probably descended from silver bream and roach and was occasionally found here and there alone, both in central Europe and in Russia. According to Kessler, Bliccopsis is also found in lake. Paleostom (at the mouth of Rion in the Caucasus). The body of the silver bream is tall, strongly compressed laterally, covered with thick, tightly fitting scales. Her head is relatively small. The mouth is small, oblique, semi-inferior, retractable.

The eyes are big. The dorsal fin is high, the anal fin is long. The back is bluish-gray, the sides and belly are silver. The dorsal, caudal and anal fins are gray, the pectoral and ventral fins are yellowish, sometimes reddish, which is how it differs in appearance from bream. In addition, the silver bream, unlike the bream, has larger scales, especially at the dorsal fin, as well as on the back; behind the back of the head it has a groove not covered with scales.

The silver bream lives in rivers, lakes and ponds. In rivers, it sticks to places with a slow flow and considerable depth, as well as in bays, backwaters, oxbow lakes, where the bottom is sandy and clay with a small admixture of silt. It is most numerous in lakes and in lowland areas of rivers. Large individuals live in bottom layers of water, deep pools, holes and in open areas of lakes and reservoirs.

The smaller silver bream prefers to stay in coastal areas among sparse thickets. At the same time, small individuals usually stay in large flocks. Gustera is characterized by a sedentary lifestyle. In summer its flocks are small. With the onset of autumn cold weather, they increase in size and move to the pits. With the onset of spring floods, its flocks go to feeding areas.

As spawning time approaches, after the water warms up, flocks of silver bream increase and move to the spawning grounds. At the same time, the lake spawning silver bream goes to the shores in large numbers, and the river bream, leaving the channel, enters small bays and creeks. The silver bream spawns from the end of April to May at a water temperature of 12-20°. During prolonged cold spells, spawning may last until June.

The white bream spawns in portions, but there are females that spawn at once. Its spawning occurs amicably, mainly in the evening and morning with a short night break. Before spawning, they become bright silver, the pectoral and ventral fins acquire an orange tint. Lumps of pearly rash appear on the head and upper body of spawning males. Soon after spawning, all mating changes disappear.

In the Dnieper, on the site of the now existing Kiev reservoir, three-year-old females of the silver bream had an average of 9.5 thousand eggs, six-year-olds - 22 thousand, and three years after the formation of the reservoir, more than 16 thousand eggs were found in three-year-old females, in six-year-olds - more than 80 thousand pieces, i.e., in the conditions of the reservoir, its fertility increased by 2-3 times.

The silver bream becomes sexually mature at two or three years of age, and in the spawning herd, males mature predominantly earlier than females. In older age groups of the spawning stock, there are significantly fewer males than females. The silver bream grows slowly. For example, in the lower reaches of the Southern Bug, yearlings had an average body length of 3.3 cm, three-yearlings - 10.2 cm, six-yearlings - 16.9 cm.

Until puberty, both sexes grow equally, but after puberty, the growth of males slows down somewhat. Juvenile silver bream in Dnieper reservoirs feed on crustaceans and chironomid larvae. To a lesser extent, it consumes algae, caddisflies, spiders and water bugs. Adult fish feed on higher aquatic plants, worms, mollusks, crustaceans, larvae and pupae of mosquitoes and other insects.

The main feeding grounds for small silver bream (10-15 cm long) are located mainly in the coastal zone. Large fish, feeding mainly on mollusks, feed in places more distant from the shore. Fish with a length of 25-32 cm, which have significant fatty deposits in their intestines, feed weaker. As the body size of the silver bream increases, the number of crustaceans and insect larvae in its food decreases and the number of mollusks increases.

It switches to feeding on mollusks when its body length is 13-15 cm or more. Depending on the composition and development of the food supply, the ratio of food organisms in the food composition of fish of the same size is not the same. For example, fish 10-12 cm long in the coastal zone feed mainly on insect larvae, and in deeper places on crustaceans, which corresponds to the distribution of these organisms in reservoirs.

White bream is widespread in Europe. It is absent in the rivers of the Arctic Ocean and in Central Asia. In the CIS it lives in the basins of the Baltic, Black, Azov and Caspian seas. In Ukraine, it lives in the basins of all rivers, excluding the rivers of Crimea and mountainous sections of other rivers.

List of fish: whitefish species muksun, omul and vendace

There are many salmon fish, one of the families is whitefish, a numerous, little-studied fish genus with variable characteristics. Representatives of this family have a laterally compressed body and a small mouth for their size, which causes a lot of inconvenience for fans of fishing with a rod. The lip of a whitefish often cannot withstand the load when it is pulled out of the water, and when the lip breaks off, the fish leaves.

Due to the similarity of the silhouette of the whitefish's head with the head of a herring, whitefish are also called herring, and only the adipose fin clearly indicates their salmon origin. The extremely high degree of variability of characters still does not allow us to establish the exact number of their species: in each lake it is possible to establish its own special species, for example, 43 forms were identified in the lakes of the Kola Peninsula alone. Currently, work is underway to combine similar forms into one species, which should lead to the systematization of fish species of the whitefish family.

General description of the family

On the territory of Russia there are over a hundred varieties of fish of this family, which have excellent taste and other beneficial properties. Its habitat is almost all bodies of water from the Kola Peninsula in the west to the Kamchatka and Chukotka Peninsulas in the east. Although this fish belongs to the salmon family, its meat is white, sometimes pinkish in color. Often, even experienced fishermen do not even suspect that the Baikal omul is the same whitefish. Here is a small list of the names of fish of the whitefish family:

largemouth and European vendace (ripus), Atlantic and Baltic whitefish;
whitefish Volkhovsky, Bauntovsky and Siberian (Pyzhyan), Baikal omul;
Muksun, Tugun, Valaamka and Chir (Shokur).

This diverse fish does not have a single appearance, but all members of the family have uniform silvery scales and darkened fins. The adipose fin, a distinctive feature of all salmonids, is also a common feature of fish of the whitefish genus. A distinctive feature of females is their scales; unlike the scales of males, they are larger and have a yellowish tint.

Like salmon, whitefish can be found in both fresh and salt water. Depending on this, two groups of whitefish are distinguished:

freshwater – lake and river;
anadromous or sea whitefish.

Gallery: whitefish species (25 photos)

Habits and preferences

A quality common to the entire family is life in a flock, which is formed according to the age of the individuals. The preferences of whitefish are unturbid, cold water enriched with oxygen, which is usually found in rapids of rivers and in the depths of lakes. At the same time, a school of whitefish can drive representatives of other fish species out of the pit. As a rule, the larger the fish, the further it moves from the shore.

The ability to spawn in fish of the family appears at the age of about three years, and in some breeds - a year or two later. Spawning of sea and freshwater whitefish takes place in the same conditions - all of them, including lake ones, rise to the upper reaches of rivers and their tributaries. Whitefish lay eggs in the fall, when the water cools to below five degrees. The spawning areas are deep holes and quiet rivers and reaches. Here the eggs are aged until spring, when the fry emerge from the eggs as the water warms.

The diet of the whitefish family, like all predators, is of animal origin: vertebrate and invertebrate insects (worms, larvae and caterpillars, caddis flies and bark beetles), small crustaceans and mollusks, caviar. Depending on the age and, accordingly, the size of the predator itself, it also attacks fish that are smaller than it. But among whitefish there are also lovers of vegetarian food collected from the bottom, as well as omnivores - semi-predators.

Their lifespan is about two decades, but fish of half their age are often caught. The largest whitefish is usually a little more than half a meter long, and small adult breeds are from one to one and a half decimeters.

As a rule, whitefish are divided into separate groups based on mouth position. The mouth can be directed upward - the upper mouth, forward - the terminal mouth, and downward - the lower mouth.

Topmouth are small fish that feed on what they find near the surface of the water. These are insects and invertebrates - worms and caterpillars. The fish with the upper mouth are represented mainly by the European vendace (ripus) and the larger Siberian one. The latter can be up to half a meter in length, lives in places where rivers flow into the salty waters of the sea, and is almost never found in lakes. The rhipus is half the size and is an inhabitant of lakes. Both species of vendace are commercially available.

Whitefish with a mouth in front (final) are also considered commercial fish. Omul is a large fish, over half a meter long, which, like vendace, lives in the bays of the seas and the estuaries of rivers flowing into the sea, where it rises to spawn. The diet of omul includes crustaceans and small fish. Baikal omul is a lake variety of whitefish. Another lake-river species is the peled fish (raw fish), it does not enter sea water, but is as large as vendace and omul, its length is about half a meter. It was also brought to the reservoirs of the Southern Urals, where its size is not so impressive. There is also a small relative of whitefish with a terminal mouth - tugun, which lives in the rivers of Siberia. Its length does not exceed twenty centimeters.

Whitefish with a lower mouth also live in Russian water bodies; there are seven species of them. But work is currently underway to separate them, and there is no point in providing any information on them.

Freshwater whitefish

The river whitefish breed - by name, is an inhabitant of rivers, where it comes from the sea or a large lake when moving to spawn. His usual weight is about a kilogram, rarely exceeds two kilograms. River whitefish only winter in lakes; at all other times of the year they lead a river life. In essence, this is a marine or anadromous whitefish acclimatized to river life. The caviar of this species of whitefish is numerous - up to 50 thousand eggs and slightly lighter than trout caviar.

Pechora whitefish, the most famous are omul, it was already mentioned above, peled, whitefish. The peled reaches a length of more than half a meter and a weight of about three kilograms. Chir is much larger, it can weigh up to ten kg, and lives in the lakes of the Pechora River basin and its channels.

The Baikal omul reaches a weight of up to seven kilograms; its food is small epishura crustaceans, and if there are insufficient quantities of them, it switches to eating small fish. Starting in September, the omul rises into the rivers, preparing for spawning. Based on the location of the spawning grounds, subspecies of the Baikal omul are distinguished:

Angara - early ripening, maturity at five years, but with slow growth;
Selenga - maturity at seven years, grows quickly;
Chivyrkuisky - also grows quickly, spawning in October.

The omul finishes spawning when slush already appears on the river and floats back to Lake Baikal for the winter. At one time, the fish was intensively caught by commercial fishermen, and its numbers decreased significantly, but now measures are being taken to artificially reproduce the omul.

All fins in fish are divided into paired, which correspond to the limbs of higher vertebrates, and unpaired. Paired fins include pectoral (P - pinna pectoralis) and ventral (V - pinna ventralis). Unpaired fins include the dorsal fin (D - p. dorsalis); anal (A - r. analis) and caudal (C - r. caudalis).

A number of fish (salmonids, characins, killer whales, etc.) have an adipose fin behind the dorsal fin; it lacks fin rays (p.adiposa).

Pectoral fins are common in bony fishes, while they are absent in moray eels and some others. Lampreys and hagfish are completely devoid of pectoral and ventral fins. In stingrays, the pectoral fins are greatly enlarged and play the main role as organs of their movement. Pectoral fins have developed especially strongly in flying fish. The three rays of the pectoral fin of the gurnard serve as legs when crawling on the ground.

The pelvic fins can occupy different positions. Abdominal position - they are located approximately in the middle of the abdomen (sharks, herring-shaped, carp-shaped). In the thoracic position, they are shifted to the front of the body (perch-shaped). Jugular position, fins located in front of the pectorals and on the throat (cod).

In some fish, the pelvic fins are transformed into spines (stickleback) or suckers (leaffish). In male sharks and rays, the posterior rays of the pelvic fins have been transformed into copulatory organs in the process of evolution. They are completely absent in eels, catfish, etc.

There may be a variable number of dorsal fins. In herring and cyprinids it is one, in mullet and perch morphs there are two, in cod morphs there are three. Their location may vary. In pike it is shifted far back, in herring and carp fish - in the middle of the body, in perch and cod - closer to the head. The longest and highest dorsal fin of the sailfish. In flounder, it looks like a long ribbon running along the entire back and, at the same time as the anal one, is their main organ of movement. Mackerel, tuna and saury have small additional fins behind the dorsal and anal fins.

Individual rays of the dorsal fin sometimes extend into long threads, and in the monkfish, the first ray of the dorsal fin is shifted to the muzzle and transformed into a kind of fishing rod, just like in the deep-sea anglerfish. The first dorsal fin of the sticky fish also moved to the head and turned into a real sucker. The dorsal fin in sedentary benthic fish species is poorly developed (catfish) or absent (stingrays, electric eels).

Tail fin:
1) isobathic – the upper and lower blades are the same (tuna, mackerel);
2) hypobate – the lower lobe is elongated (flying fish);
3) epibate – the upper lobe is elongated (sharks, sturgeons).

Types of caudal fins: forked (herring), notched (salmon), truncated (cod), rounded (burbot, gobies), semilunate (tuna, mackerel), pointed (elpout).

From the very beginning, the fins have been assigned the function of movement and maintaining balance, but sometimes they also perform other functions. The main fins are dorsal, caudal, anal, two ventral and two pectoral. They are divided into unpaired - dorsal, anal and caudal, and paired - pectoral and abdominal. Some species also have an adipose fin located between the dorsal and caudal fins. All fins are driven by muscles. In many species, the fins are often modified. Thus, in male viviparous fish, the modified anal fin has turned into a mating organ; some species have well-developed pectoral fins, which allows the fish to jump out of the water. Gourami have special tentacles, which are thread-like pelvic fins. And some species that burrow into the ground often lack fins. Guppy tail fins are also an interesting creation of nature (there are about 15 species of them and their number is growing all the time). The movement of the fish begins with the tail and caudal fin, which send the body of the fish forward with a strong blow. The dorsal and anal fins provide balance to the body. The pectoral fins move the body of the fish during slow swimming, serve as a rudder, and, together with the pelvic and caudal fins, ensure the equilibrium position of the body when it is at rest. In addition, some species of fish can rely on pectoral fins or move with their help on hard surfaces. The pelvic fins perform mainly a balancing function, but in some species they are modified into a suction disc, which allows the fish to stick to a hard surface.

1. Dorsal fin.

2. Adipose fin.

3. Caudal fin.

4. Pectoral fin.

5. Pelvic fin.

6. Anal fin.

The structure of a fish. Types of tail fins:

Truncated

Split

Lyre-shaped

24. Structure of fish skin. The structure of the main types of fish scales, their functions.

Fish skin performs a number of important functions. Located on the border between the external and internal environments of the body, it protects the fish from external influences. At the same time, separating the fish body from the surrounding liquid environment with chemicals dissolved in it, the fish skin is an effective homeostatic mechanism.

Fish skin quickly regenerates. Through the skin, on the one hand, partial release of the final metabolic products occurs, and on the other, the absorption of certain substances from the external environment (oxygen, carbonic acid, water, sulfur, phosphorus, calcium and other elements that play a large role in life). The skin plays an important role as a receptor surface: thermo-, barochemo- and other receptors are located in it. In the thickness of the corium, the integumentary bones of the skull and pectoral fin girdles are formed.

In fish, the skin also performs a rather specific – supporting – function. Muscle fibers of skeletal muscles are attached to the inner side of the skin. Thus, it acts as a supporting element in the musculoskeletal system.

Fish skin consists of two layers: an outer layer of epithelial cells, or epidermis, and an inner layer of connective tissue cells - the skin itself, dermis, corium, cutis. Between them there is a basement membrane. The skin is underlain by a loose connective tissue layer (subcutaneous connective tissue, subcutaneous tissue). In many fish, fat is deposited in the subcutaneous tissue.

The epidermis of fish skin is represented by multilayer epithelium, consisting of 2–15 rows of cells. The cells of the upper layer of the epidermis are flat in shape. The lower (germ) layer is represented by one row of cylindrical cells, which, in turn, originate from the prismatic cells of the basement membrane. The middle layer of the epidermis consists of several rows of cells, the shape of which varies from cylindrical to flat.

The outermost layer of epithelial cells becomes keratinized, but unlike terrestrial vertebrates in fish, it does not die, maintaining contact with living cells. During the life of a fish, the intensity of keratinization of the epidermis does not remain unchanged; it reaches its greatest degree in some fish before spawning: for example, in male cyprinids and whitefishes, the so-called Pearly rash is a mass of small white bumps that make the skin feel rough. After spawning it disappears.

The dermis (cutis) consists of three layers: a thin upper (connective tissue), a thick middle mesh layer of collagen and elastin fibers and a thin basal layer of tall prismatic cells, giving rise to the two upper layers.

In active pelagic fish the dermis is well developed. Its thickness in areas of the body that provide intense movement (for example, on the caudal peduncle of a shark) is greatly increased. The middle layer of the dermis in active swimmers can be represented by several rows of strong collagen fibers, which are also connected to each other by transverse fibers.

In slow-swimming littoral and bottom-dwelling fish, the dermis is loose or generally underdeveloped. In fast-swimming fish, there is no subcutaneous tissue in the parts of the body that provide swimming (for example, the caudal peduncle). In these places, muscle fibers are attached to the dermis. In other fish (most often slow ones), the subcutaneous tissue is well developed.

The structure of fish scales:

Placoid (it is very ancient);

Ganoid;

Cycloid;

Ctenoid (youngest).

Placoid fish scales

Placoid fish scales(photo above) is characteristic of modern and fossil cartilaginous fish - and these are sharks and rays. Each such scale has a plate and a spine sitting on it, the tip of which extends out through the epidermis. The basis of this scale is dentin. The spike itself is covered with even harder enamel. The placoid scale inside has a cavity that is filled with pulp - pulp, it has blood vessels and nerve endings.

Ganoid fish scales

Ganoid fish scales has the appearance of a rhombic plate and the scales are connected to each other, forming a dense shell on the fish. Each such scale consists of a very hard substance - the upper part is made of ganoine, and the lower part is made of bone. A large number of fossil fish have this type of scale, as well as the upper parts in the caudal fin of modern sturgeon.

Cycloid fish scales

Cycloid fish scales found in bony fish and does not have a ganoine layer.

Cycloid scales have a rounded neck with a smooth surface.

Ctenoid fish scales

Ctenoid fish scales also found in bony fish and does not have a layer of ganoine; it has spines on the back side. Usually the scales of these fish are arranged in a tiled manner, and each scale is covered in front and on both sides by the same scales. It turns out that the rear end of the scale comes out, but underneath it is lined with another scale and this type of cover preserves the flexibility and mobility of the fish. Annual rings on the scales of a fish allow one to determine its age.

The arrangement of scales on the body of a fish occurs in rows, and the number of rows and the number of scales in a longitudinal row does not change with changes in the age of the fish, which is an important systematic feature for different species. Let's take this example - the lateral line of a golden crucian carp has 32-36 scales, while a pike has 111-148.

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