Living conditions in various areas of fresh water, especially in the sea, leave a sharp imprint on the fish living in these areas.
Fish can be divided into marine, anadromous, semi-anadromous, or estuarine fish, brackish water and freshwater fish. Already significant differences in salinity are important for the distribution of individual species. The same is true for the differences in other properties of water: temperature, lighting, depth, etc. Trout requires a different water than barbel or carp; tench and crucian carp also keep in such bodies of water where perch cannot live because of too warm and muddy water; The asp requires clean, flowing water with fast ripples, and the pike can stay in stagnant water overgrown with grass. Our lakes, depending on the living conditions in them, can be distinguished as pike-perch, bream, crucian, etc. Inside more or less large lakes and rivers, we can note different zones: coastal, open water and bottom, characterized by different fish. Fish from one zone can enter another zone, but in each zone one or another species composition prevails. The coastal zone is richest. The abundance of vegetation, hence food, makes this area favorable for many fish; here they feed, here they throw an acre. Distribution of fish by zones plays an important role in fisheries. For example, burbot (Lota lota) is a bottom fish, and it is caught from the bottom with venters, but not with flowing nets, which are used to catch asp, etc. Most whitefishes (Coregonus) feed on small planktonic organisms, mainly crustaceans. Therefore, their habitat depends on the movement of plankton. In winter they leave after the latter to the depth, in spring they rise to the surface. In Switzerland, biologists have indicated the places where planktonic crustaceans live in winter, and here the whitefish fishery arose after that; On Baikal, omul (Coregonus migratorius) is caught with nets in winter at a depth of 400-600 m.
The delimitation of a zone in the sea is more pronounced. According to the living conditions that it provides for organisms, the sea can be divided into three zones: 1) littoral, or coastal; 2) pelagic, or open sea zone; 3) abyssal, or deep. The so-called sublittoral zone, which constitutes the transition from coastal to deep, already reveals all the signs of the latter. Their boundary is a depth of 360 m.The coastal zone starts from the coast and extends to a vertical plane that bounds an area deeper than 350 m.The open sea zone will be outward from this plane and up from another plane lying horizontally at a depth of 350 m The deep zone will be below from this last (Fig. 186).

For all life has great value light. Since water weakly transmits the rays of the sun, conditions of existence unfavorable for life are created in the water at a certain depth. According to the intensity of illumination, as indicated above, three light zones are distinguished: euphotic, dysphotic and aphotic.
Free-swimming and near-bottom forms are closely intermixed near the coast. Here is the cradle of marine animals, from here clumsy bottom dwellers and nimble swimmers of the open sea arise. Thus, off the coast, we find a rather diverse mixture of types. But the living conditions on the open sea and at depths are very different, and the types of animals, in particular, fish, in these zones are very different from each other. All animals that live on the bottom of the sea, we call one name: benthos. These include crawling to the bottom, lying on the bottom, burrowing forms (mobile benthos) and sessile forms (sessile benthos: corals, sea anemones, tubular worms, etc.).
Those organisms that can swim freely are called pectons. The third group of organisms, devoid or almost devoid of the ability to move actively, clinging to algae or helplessly carried in the wind or currents, is called planktol. Among fish, we have forms belonging to all three groups of organisms.
Non-lagic fish are nekton and plankton. Organisms living in water independently of the bottom, not associated with it, are called non-lagic. This group includes organisms both living on the surface of the sea and in its deeper layers; organisms actively swimming (nekton), and organisms carried by the wind and currents (plankton). Deeply living pelagic animals are called bathinelagic.
The conditions of life on the open sea are characterized primarily by the fact that there is no surf here, and animals do not need to develop adaptations to keep them at the bottom. The predator has nowhere to hide here, trapping the prey, the latter has nowhere to hide from predators. Both must rely mainly on their own speed. Most of the fish on the high seas are therefore excellent swimmers. This is firstly; secondly, coloring sea ​​water, blue in both transmitted and incident light influences the coloration of pelagic organisms in general and fish in particular.
Adaptations of nekton fish for movement are different. We can distinguish several types of nekton fish.
In all of these types, the ability to swim quickly is achieved in different ways.
The type is spindle-shaped, or torpedo-shaped. The organ of movement is the tail section of the body. Examples of this type are: herring shark (Lamna cornubica), mackerel (Scomber scomber), salmon (Salmo salar), herring (Clupea harengus), cod (Gadus morrhua).
The type is ribbon-like. Movements occur with the help of serpentine movements of a long, ribbon-like body compressed from the sides. For the most part, they are inhabitants of rather great depths. Example: king herring, or belt fish (Regalecus banksii).
Arrow-shaped type. The body is elongated, the snout is pointed, strong unpaired fins are carried back and arranged in the form of an arrow feather, making up one piece with the caudal fin. Example: common garfish (Belone belone).
Sail-shaped type. The snout is elongated, unpaired fins and general form like in the previous one, the front dorsal fin is greatly enlarged and can serve as a sail. Example: sailboat (Histiophorus gladius, fig. 187). This also includes the swordfish (Xiphias gladius).

A fish is essentially an animal that actively swims. Therefore, there are no real planktonic forms among them. We can distinguish the following types of fish approaching plankton.
The type is needle-shaped. Active movements are weakened, performed with the help of rapid bends of the body or undulating movements of the dorsal and anal fins. Example: Pelagic needlefish (Syngnathus pelagicus) of the Sargasso Sea.
The type is compressed-symmetrical. The body is tall. The dorsal and anal fins are opposite each other, high. Most of the pelvic fins are absent. Movement is very limited. Example: moonfish (Mola mola). This fish also lacks a caudal fin.
He does not make active movements, the muscles are largely atrophied.
The type is spherical. The body is spherical. In some fish, the body may swell due to the ingestion of air. Example: hedgehog fish (Diodon) or deep-sea melanocetus (Melanocetus) (fig. 188).

There are no true planktonic forms among adult fish. But they are found among planktonic eggs and larvae of planktonic fish. The body's ability to stay in water depends on a number of reasons. First of all, the specific gravity of water is important. The body keeps on water, according to Archimedes' law, if its specific gravity is not more specific gravity water. If the specific gravity is greater, then the body sinks at a rate proportional to the difference in specific gravity. The sink rate, however, will not always be the same. (Small grains of sand sink more slowly than large stones of the same specific gravity.)
This phenomenon depends, on the one hand, on the so-called viscosity of water, or, internal friction, on the other, on what is called surface friction of bodies. The larger the surface of an object in comparison with its volume, the greater its surface resistance, and it sinks more slowly. The low specific gravity and high viscosity of the water resist immersion. As is known, copepods and radiolarians are excellent examples of such a change. We observe the same phenomenon in eggs and in fish larvae.
Pelagic eggs are mostly small. The eggs of many pelagic fish are equipped with filamentous outgrowths that prevent them from submerging, for example, eggs of the mackerel fishes (Scombresox) (Fig. 189). The larvae of some fish leading a pelagic lifestyle have a device for keeping on the surface of the water in the form of long filaments, outgrowths, etc. Such are the pelagic larvae of the deep-sea fish Trachypterus. In addition, the epithelium of these larvae is changed in a very peculiar way: its cells are almost devoid of protoplasm and are stretched to enormous sizes with liquid, which, of course, by reducing the specific gravity, also contributes to the retention of the larvae in the water.

Another condition affects the ability of organisms to stay on water: osmotic pressure, which depends on temperature and salinity. With a high salt content in the cell, the latter absorbs water, and, although it becomes heavier, its specific gravity decreases. Once in saltier water, the cell, on the contrary, decreases in volume and becomes heavier. The pelagic eggs of many fish contain up to 90% water. Chemical analysis has shown that in the eggs of many fish, the amount of water decreases with the development of the larva. As the water becomes depleted, the developing larvae sink deeper and, finally, sit on the bottom. The transparency and lightness of the cod (Gadus) larvae are due to the presence of a vast subcutaneous space filled with aqueous humor and extending from the head and yolk sac to the posterior end of the body. The eel larva (Anguilla) has the same vast space between the skin and muscles. All of these devices undoubtedly reduce weight and impede diving. Ho and with a high specific gravity, an organism will stick to water if it presents sufficient surface resistance. This is achieved, as said, by increasing the volume and changing the shape.
Deposits of fat and oil in the body, serving as a food reserve, at the same time, reduce its specific gravity. Eggs and juveniles of many fish show this adaptation. Pelagic eggs do not stick to objects, they swim freely; many of them contain a large drop of fat on the surface of the yolk. These are the eggs of many cod fish: the common fish (Brosmius brosme), often found in Murman; moth (Molva molva), which is caught there; such are the eggs of mackerels (Scomber scomber) and other fish.
Air bubbles of all kinds serve the same purpose - to reduce the specific gravity. This includes, of course, the swim bladder.
Eggs are built of a completely different type, submerged - demersal, developing at the bottom. They are larger, heavier, darker, while pelagic eggs are transparent. Their shell is often sticky, so that these eggs stick to rocks, algae and other objects, or to each other. In some fish, like the garfish (Belone belone), the eggs are also equipped with numerous filamentous outgrowths that serve to attach to algae and to each other. In smelt (Osmerus eperlanus), eggs are attached to rocks and rocks by the outer shell of the egg, which is detached, but not completely, from the inner membrane. Large eggs of sharks and rays also adhere. The eggs of some fish, such as salmon (Salmo salar), are large, separate and do not stick to anything.
Bottom fish, or benthos fish. Fish living at the bottom near the coast, as well as pelagic ones, represent several types of adaptation to their living conditions. Their main conditions are as follows: first, the constant danger of being thrown by the surf or in a storm ashore. Hence the need arises to develop the ability to hold onto the bottom. Secondly, the danger of being smashed against stones; hence the need to acquire armor. Fish living on the muddy bottom and digging in it develop various adaptations: some for digging and for moving in the mud, and others for catching prey, buried in the mud. Some fish have adaptations to hide among algae and corals growing among the banks and at the bottom, while others - for burying in the sand at low tide.
We distinguish between the following types of bottom fish.
The type is dorsoventrally flattened. The body is compressed from the dorsal side to the ventral side. The eyes are moved to the upper side. The fish can nestle closely to the bottom. Example: stingrays (Raja, Trygon, etc.), and from bony fish- sea devil (Lophius piscatorius).
Longtail type. The body is strongly elongated, the highest part of the body is behind the head, gradually becomes thinner and ends in a sharpness. The apal and dorsal fins form a long fin fringe. The type is common among deep sea fish... Example: longtail (Macrurus norvegicus) (Fig. 190).
Compressed asymmetric type. The body is laterally compressed, bordered by long dorsal and anal fins. The eyes are on one side of the body. In youth, they have a squeezed-symmetrical body. There is no swim bladder, they stay at the bottom. This includes the flounder family (Pleuronectidae). Example: turbot (Rhombus maximus).

The type is acne-like. The body is very long, serpentine; paired fins are rudimentary or absent. Bottom fish. The movement along the bottom created the same shape that we see in snakes among reptiles. Examples are eel (Anguilla anguilla), lamprey (Petromyzon fluviatilis).
The type is asteroleptic. The front half of the body is enclosed in a bony armor, which reduces active movement to a minimum. The body is triangular in cross-section. Example: box body (Ostracion cornutus).
Special conditions prevail at great depths: tremendous pressure, absolute absence of light, low temperature (up to 2 °), complete calmness and absence of movement in the water (except for the very slow movement of the entire mass of water from the Arctic seas to the equator), and the absence of plants. These conditions impose a sharp imprint on the organization of fish, creating a special character of the deep fauna. Their muscular system is poorly developed, the bone is soft. The eyes are sometimes reduced to complete disappearance. In those deep-seated fish in which the eyes are preserved, the retina is similar in the absence of cones and the position of the pigment to the eye of nocturnal animals. Further, deep-seated fish are distinguished by a large head and a slender body, thinning towards the end (long-tail type), a large expandable stomach and very large teeth in the mouth (Fig. 191).

Deep-seated fish can be divided into benthic and bathypelagic fish. Bottom fish of the depths include representatives of stingrays (cat. Turpedinidae), flounders (family Pleuronectidae), hand-footed fishes (family Pediculati), shell-cheeks (Cataphracti), long-tailed (family Macruridae), eelpouts (family Zoarcidae), codfish (family Zoarcidae) Gadidae), etc. Ho both among bathypelagic and coastal fish there are representatives of these families. It is not always easy to draw a sharp, distinct boundary between deep-seated and coastal forms. Many forms are found here and there. Also, the depth at which bathypelagic forms are encountered varies within wide limits. Of the bathypelagic fish, mention should be made of the luminous anchovies (Scopelidae).
Bottom fish feed on sedentary animals and their remains; it does not require expenditure of energy, and bottom fish usually keep in large schools. On the contrary, bathypelagic fish find their food with difficulty and keep one by one.
Most of the commercial fish belong to either the littoral or pelagic fauna. Some cod (Gadidae), mullet (Mugilidae), flounder (Pleuronectidae) belong to the coastal zone; tuna (Thynnus), mackerel (Scombridae) and the main commercial fish - herring (Clupeidae) - belong to the pelagic fauna.
Of course, not all fish necessarily belong to one of these types. Many fish only approach one or another of them. A clearly pronounced type of structure is the result of adaptation to certain, strictly isolated conditions of habitat and movement. And such conditions are not always well expressed. On the other hand, it takes a long time for this or that type to develop. A fish that has recently changed its habitat may partly lose its former adaptive type, but not yet develop a new one.
Fresh water does not have the same variety of living conditions that is observed in the sea, however, there are several types among freshwater fish. For example, the dace (Leuciscus leuciscus), which prefers to stick to a more or less strong current, has a type approaching fusiform. On the contrary, the bream (Abramis brama) or crucian carp (Carassius carassius) belonging to the same family of cyprinids (Cyprinidac) - sedentary fish living among aquatic plants, roots and under steep fishes - have an awkward body, squeezed from the sides, like in reef fish. The pike (Esox lucius), a predator rapidly rushing towards its prey, resembles the arrow-shaped type of nekton fish; living in type and silt, the loach (Misgurnus fossilis) reptile at the bottom has a more or less eel-like shape. The sterlet (Acipenser ruthenus), constantly reptile along the bottom, resembles the longtail type.

In the cold and dark depths of the oceans, the water pressure is so great that no land animal could withstand it. Despite this, there are creatures that have been able to adapt to such conditions.
A variety of biotopes can be found in the sea. In marine depths in the tropical zone, the water temperature reaches 1.5-5 ° C, in the polar regions it can drop below zero.
A wide variety of life forms are presented at a depth below the surface, where sunlight is still able to receive the possibility of photosynthesis, and, therefore, gives life to plants, which are the initial element of the trophic chain in the sea.
There are incomparably more animals in tropical seas than in arctic waters. The deeper the species diversity becomes poorer, less light, colder water, and higher pressure. At a depth of two hundred to a thousand meters, about 1000 species of fish live, and at a depth of one thousand to four thousand meters, there are already only one hundred and fifty species.
The belt of waters from three hundred to a thousand meters deep, where semi-darkness reigns, is called the mesopelagiallu. At a depth of more than a thousand meters, darkness is already falling, the waves of the water here are very weak, and the pressure reaches 1 ton of 265 kilograms per square centimeter. Deep-sea shrimps of the genus MoIOBiotiz, cuttlefish, sharks and other fish, as well as numerous invertebrates live at such a depth.

OR YOU KNOW THAT ...

The dive record belongs to the cartilaginous fish Basogigas, which was sighted at a depth of 7965 meters.
Most deep-sea invertebrates are black in color, while most deep-sea fish are brown or black. Thanks to this protective coloration, they absorb the bluish-green light of the deep waters.
Many deep sea fish have air-filled swim bladders. And until now, researchers do not understand how these animals withstand the enormous pressure of water.
Males of some species of deep-sea anglerfish attach with their mouths to the belly of larger females and grow to them. As a result, the man remains attached to the female for the rest of his life, eats at her expense, and even the circulatory system becomes common. And the female, thanks to this, does not have to look for the male during the spawning period.
One eye of a deep-sea squid that lives near the British Isles is significantly larger than the other. With the help of a large eye, he orients himself to the depth, and he uses the second eye when he rises to the surface.

Eternal twilight reigns in the depths of the sea, but in the water different colors numerous inhabitants of these biotopes glow. The glow helps them attract mate, prey, and scare off enemies. The glow of living organisms is called bioluminescence.
BIOLUMINESIENCE

Many species of animals that inhabit the dark depths of the sea can emit their own light. This phenomenon is called the visible glow of living organisms, or bioluminescence. It is caused by the enzyme luciferase, which catalyzes the oxidation of substances produced by the light-luciferin reaction. Animals can create this so-called "cold light" in two ways. Substances necessary for bioluminescence, found in their body or in the body of luminous bacteria. In the European anglerfish, light-emitting bacteria are contained in vesicles at the end of the dorsal fin that grows in front of the mouth. Bacteria need oxygen to glow. When the fish does not intend to emit light, it closes off the blood vessels that lead to the bacteria in the body. The scalpelus spotted fish (Phyrobiopathic rapebrais) carries billions of bacteria in special bags under the eyes; with the help of special leather folds, the fish completely or partially covers these bags, regulating the intensity of the emitted light. To enhance the glow, many crustaceans, fish and squid have special lenses or a layer of cells that reflect light. The inhabitants of the depths use bioluminescence in different ways. Deep-sea fish glow in different colors. For example, the photophores of ribsokirok emit greenish, and photophores of the Astronest - violet-blue.
SEARCH PARTNER
The inhabitants of the deep sea resort to different ways attracting a partner in the dark. Light, smell and sound play an important role in this. In order not to lose the female, males even use special techniques... The relationship between males and females is interesting. Better studied the life of the European anglerfish. Males of this species usually find a large female without problems. With their large eyes, they notice its typical light signals. Having found a female, the male firmly attaches to her and grows to her body. From that time on, he leads an attached lifestyle, even feeds through the female's circulatory system. When the female anglerfish lays eggs, the male is always ready to fertilize it. Males of other deep-sea fish, for example, gonostomids, are also smaller than females, in some of them the sense of smell is well developed. Researchers believe that in this case, the female leaves behind a scent trail that the male finds. Sometimes males of the European anglerfish are also found by the smell of females. In water, sounds are carried over a long distance. That is why males of three-headed and toad-like fins move their fins in a special way and make a sound that should attract the attention of the female. Toad-fish give out beeps, which are transmitted as "boop".

At this depth, there is no light, and no plants grow here. Animals that live in the depths of the sea can only hunt the same deep-sea inhabitants or feed on carrion and organic debris that decays. Many of them, such as sea cucumbers, starfish and bivalve molluscs, feed on microorganisms, which they filter out of the water. Cuttlefish usually prey on crustaceans.
Many species of deep-sea fish eat each other or hunt small prey for themselves. Fish that feed on molluscs and crustaceans must have strong teeth to crush the shells that protect the soft bodies of their prey. Many fish have a lure located directly in front of the mouth, glows and attracts prey. By the way, if you are interested in an online store for animals. please contact.

Deep sea fish are considered one of the most amazing creatures on the planet. Their uniqueness is primarily due to the harsh living conditions. That is why the depths of the world's oceans, and especially deep-sea depressions and trenches, are not densely populated at all.

and their adaptation to the conditions of existence

As already mentioned, the depths of the oceans are not as densely populated as, say, the upper layers of water. And there are reasons for this. The fact is that the conditions of existence change with depth, which means that organisms must have some adaptations.

1. Living in the dark. With depth, the amount of light decreases sharply. It is believed that the maximum distance that a sunbeam travels in water is 1000 meters. No traces of light were found below this level. Therefore, deep-sea fish are adapted to life in complete darkness. Some fish have no functioning eyes at all. The eyes of other representatives, on the contrary, are very developed, which makes it possible to catch even the weakest light waves. Another interesting device is fluorescent organs, which can glow using energy. chemical reactions... Such light not only facilitates movement, but also attracts potential prey.
2. High pressure. Another feature of deep-sea existence. That is why the internal pressure of such fish is much higher than that of their shallow-water relatives.
3. Low temperature. With depth, the water temperature drops significantly, so fish are adapted to life in such an environment.
4. Lack of food. Since the diversity of species and the number of organisms decreases with depth, very little food remains. Therefore, deep-sea fish have supersensitive organs of hearing and touch. This gives them the ability to detect potential prey at a great distance, which in some cases is measured in kilometers. By the way, such a device makes it possible to quickly hide from a larger predator.

You can see that fish living in the depths of the ocean are truly unique organisms. In fact, a huge area of ​​the world's oceans still remains unexplored. That is why the exact number of deep-sea fish species is unknown.

Variety of fish living in the depths of water

Although modern scientists know only a small part of the population of the depths, there is information about some very exotic inhabitants of the ocean.

Batizaurus- the deepest predatory fish, living at a depth of 600 to 3500 m. They live in tropical and subtropical waters. This fish has almost transparent skin, large, well-developed sensory organs, and its mouth is littered with sharp teeth (even tissues of the palate and tongue). Representatives of this species are hermaphrodites.

Viper fish Is another unique representative of the underwater depths. She lives at a depth of 2800 meters. It is with these species that the depth is inhabited. The main feature of the animal is huge fangs, which are somewhat reminiscent of the poisonous teeth of snakes. This species is adapted for existence without constant nutrition - the stomachs of fish are so stretched that they can completely swallow a living creature much larger than themselves. And on the tail of the fish there is a specific luminous organ, with the help of which they lure prey.

Angler - a rather unpleasant-looking creature with huge jaws, a small body and poorly developed muscles. Inhabits on Since this fish cannot actively hunt, it has developed special adaptations. has a special luminous organ that releases certain chemicals. Potential prey reacts to light, swims up, after which the predator swallows it completely.

In fact, there are much more depths, but not much is known about their way of life. The fact is that most of them can exist only under certain conditions, in particular, at high pressure. Therefore, it is not possible to extract and study them - when they rise to the upper layers of the water, they simply die.

Fish - inhabitants of the aquatic environment

Fish live in water, water has a significant density and it is more difficult to move in it than in air.

What kind of fish should be in order to survive in the aquatic environment?

The fish are characterized by:

• Buoyancy
• Streamlined
• Slip
• Infection protection
• Orientation in the environment

Buoyancy

1. Fusiform body shape
2. The body is compressed from the sides, streamlined
3. Fins

Streamline and Slip:

Tiled scales

Bactericidal mucus

Fish movement speed

The fastest fish - sailfish She swims faster than a cheetah runs.

The speed of the sailfish is 109 km / h (for the cheetah - 100 km / h)

Merlin - 92 km / h

Fish - wahoo - 77.6 km / hour

Trout - 32 km / h faster than pike.

Marena - 19 km / h faster

Pike - 21 km / h

Crucian - 13 km / h

Did you know that ...

The silvery-white color of fish and the shine of the scales largely depend on the presence of guanine (an amino acid, a protein breakdown product) in the skin. The color changes from habitat, age, and health of the fish.

Most fish have a silvery color, while the abdomen is light and the back is dark. Why?

Protection from predators - dark back and light belly

The senses of fish

Vision

The fish's eyes can see only at close range due to the spherical lens, close to the flat cornea, which is an adaptation to vision in the aquatic environment. Usually the eyes of a fish are "set" for vision at 1 m, but due to the contraction of smooth muscle fibers, the lens can be pulled back, thereby achieving visibility at a distance of up to 10-12 m.

2) German ichthyologists (scientists studying fish) have found that fish are good at distinguishing colors, incl. and red.

Flounder bypasses red, light green, blue and yellow nets. But the fish probably does not see the gray, dark green and blue nets.

Smell and taste

1) The taste organs of fish are found in the mouth, on the lips, on the scalp, on the body, on the antennae and on the fins. They determine, first of all, the taste of the water.

2) The organs of smell are paired sacs in the front of the skull. Outwardly, they open with nostrils. The sense of smell in fish is 3-5 times thinner than in dogs.

Fish can establish the presence of vital substances at a distance of 20 km. Salmon catches the smell of its native river from a distance of 800 km from its mouth

Side line

1) A special organ runs along the sides of the fish - the lateral line. It serves as an organ of balance and for orientation in space.

Hearing

Scientist Karl Frisch studied not only vision, but also hearing of fish. He noticed that his blind fish for experiments always floated up when they heard the whistle. Pisces are very good at hearing. Their ear is called the inner ear and is located inside the skull.

Norwegian scientists have found that some fish species are able to distinguish sound vibrations from 16 to 0.1 Hz. This is 1000 times the sensitivity of the human ear. It is this ability that helps fish to navigate well in troubled waters and at great depths.

Many fish make sounds.

Scenes hum, grunt, squeak. When a flock of scien swims at a depth of 10-12m, a moo is heard

Marine Warrant Officer - hisses and croaks

Tropical flounders emit the sounds of a harp, bell ringing

Talk like fish:

Black crucian carp - Khryap-Khryap

Light croaker - try-try-try

Sea rooster - track-track-track or ao-ao-hrr-hrr-ao-ao - hrr-hrr

River catfish - oink-oink-oink

Sea carp - quack-quack-quack

Sprat - oo-oo-oo-oo-oo-oo

Cod - tweet-tweet-tweet (quiet)

Herring - whisper quietly (tsh - tsh-tsh)

The adaptability of fish to life in water is manifested, first of all, in the streamlined shape of the body, which creates the least resistance during movement. This is facilitated by a cover of scales covered with mucus. The caudal fin as an organ of movement and the pectoral and pelvic fins ensure excellent maneuverability of the fish. The lateral line allows you to confidently navigate even in muddy water, without bumping into obstacles. The absence of external hearing organs is associated with good sound propagation in the aquatic environment. The vision of fish allows them to see not only what is in the water, but also to notice the threat on the shore. The sense of smell allows you to detect prey at great distances (for example, sharks).

Respiratory organs, gills, provide the body with oxygen in conditions of low oxygen content (compared to air). The swimbladder acts as a hydrostatic organ, allowing the body to maintain its density at different depths.

Fertilization is external, except for sharks. Some fish have viviparity.

Artificial breeding is used to restore the population of anadromous fish on rivers with hydroelectric power plants, primarily in the lower reaches of the Volga. Breeders going for spawning are caught from the dam, reared in closed reservoirs and released into the Volga.

Carp is also bred for commercial purposes. Silver carp (strains unicellular algae) and grass carp (it feeds on underwater and emerging vegetation) allow you to get products with minimal feeding costs.