What sense organs do fish have: let’s look at the question

How do fish feel?

Pisces are amazing creatures of ancient origin. Surely you all know that life originated in the World Ocean. Over time, some of the inhabitants, during the course of evolution, left the aquatic “cradle”, but the ancestors of modern fish preferred to remain in their familiar environment. Millennia passed, land inhabitants became more and more improved and formed new classes, families and species. Evolution also affected fish, improving their mechanisms of adaptation to the water element and sensory skills.

Vision

In everyday life, we are most accustomed to relying on vision: we receive the lion's share of information with the help of our eyes. Fish have a slightly different situation: this feeling plays a less important role in their lives, although there are very few of them who are completely blind (with the exception of the deepest-sea species).

The eyes of fish are arranged in a way that is familiar to us: the iris, the pupil (unlike ours - in most species it does not respond to the degree of illumination), the lens, the retina. The retina consists of photoreceptors (rods and cones), which are responsible for image quality.

Let's briefly go over the main characteristics of the vision of the average inhabitant of a pond:

Even a person who is far from fishing knows that making noise on the shore is highly discouraged. However, aquatic inhabitants feel great under bridges where heavy truck traffic is organized and in ponds near populated areas. Perhaps they don't hear anything? No, representatives of the ichthyofauna simply get used to background sounds and do not react in any way to ordinary noises.

The swim bladder is an additional resonator, and the lateral line allows us to perceive low-frequency vibrations inaccessible to our hearing. But the upper threshold of perception in fish is also lower: predators do not hear sounds above 500 Hz, white fish - 2 kHz. At the same time, we are able to perceive waves with a frequency of up to 20 kHz!

Smell

Most freshwater fish have external and internal olfactory organs, which they rely on more than their eyes. They pass water through the nostrils (usually there are two of them) and, using the corresponding receptors located in the olfactory folds, analyze microdoses of various substances dissolved in it. Believe it or not, the sense of smell in some species of fish is no worse developed than in the recognized “sniffers” of the land world, dogs.

The undoubted champion in this category is the river catfish, but other representatives of the ichthyofauna known to us can distinguish odors much better than you and I. Thanks to this feeling, they find food, choose partners during the breeding season, and escape from natural enemies.

A shark can smell blood, and a carp can smell fresh grass from several kilometers away. This is used by fishermen when selecting baits: aromatic additives that attract fish, called attractants or bite activators, are widely used. But no attractant is capable of eliminating an odor that is unattractive to fish, so soured, stale or otherwise spoiled baits are prohibited.

High sensitivity to odors – that’s another thing! Fish are able to analyze even the chemical composition of water, the degree of its saturation with oxygen and other parameters! This allows the same salmon to accurately find the rivers in which they were born, and eels to accurately rush into the Sargasso Sea thousands of kilometers away. True, this sense cannot be called smell in the usual sense of the word, but what difference does it make: fish successfully use it in the process of survival.

Fish can obtain almost exhaustive information about a potentially edible object, guided solely by their sense of smell. However, taste also plays an important role in the feeding behavior of most representatives of the ichthyofauna. Fish are excellent at distinguishing tastes: bitter, sweet, sour, salty. Moreover: they sense flavors much more subtly than you and I.

When approaching a potentially edible object, fish usually explore it using external taste buds located on the lips, antennae, gills, head, and sometimes even fins. The same carps “savor” the offered food for a long time, driving water with nutrients dissolved in it through the gills.

Of course, if a fish is very hungry, it neglects to explore the delicacy using its external senses, immediately grabbing the food and only then analyzing the taste using receptors located in the mouth (like ours). If the taste of the bait does not correlate with the smell it emits, it is quite possible that the representative of the ichthyofauna will spit out the offered delicacy with indignation.

Touch

Pisces, like you and me, are able to feel touch, pain, and temperature fluctuations. This is necessary to ensure survival: the fish is forced to react to pain and temperature fluctuations. Remember how, having been pricked by a hook, it releases dubious prey from its mouth. True, the nervous system of representatives of the ichthyofauna is not highly developed, therefore their pain threshold is low.

The corresponding tactile and temperature receptors are located throughout the body of the fish: from the upper layers of the skin and fins to the mucous membranes and soft tissues. Thermoreceptors, which are sensitive to temperature changes, play a special role in the survival process. The fact is that fish are cold-blooded creatures, and they do not know how to maintain body temperature like you and me. Therefore, they must somehow adapt.

Side line

The lateral line is a truly unique sensory organ, inherent exclusively to representatives of the ichthyofauna and some amphibians that almost constantly live in water. Have you seen a line in fish that runs along the sides on both sides approximately in the middle of the body? This main channel is literally dotted with receptors responsible for seismosensory. Their external conclusions are located on the scales and head, and neurons connect them to the brain.

The lateral line can be continuous and clearly visible, it can be interrupted, and in some fish it can even be located in an atypical place. For example, in herring, seismosensory organs are located on the head.

During the experiments, it was noticed that even after losing their sight, many fish feel quite well. The lateral line allows them to distinguish the slightest fluctuations in the environment, including subtly detecting changes in the direction of water flow. As a result, fish do not bump into obstacles even in complete darkness or muddy water, recognize the characteristic vibrations emitted by potential prey (for example, the swarming of bloodworms in the bottom silt), and react sensitively to the approach of a predator.

For example, if a pike is deprived of its vision, it will continue to hunt quite successfully, relying on other senses. But if you destroy its lateral line, the predator, even if it is very hungry, will not react to the tasty fish frolicking nearby.

Conclusion: you need to try not to create alarming vibrations in the water, that is, do not stomp on the shore, walk quietly on the ice, and be careful in the boat.

Electroreception

Some fish are capable of generating a weak electromagnetic field. Electric eels, stingrays, and catfish have similar organs. These fish are surrounded by an electromagnetic field, and they are sensitive to its disturbance caused by the impact of various objects.

For example, the Nile is home to an amazing fish called the longsnout or water elephant. But the most amazing thing about it is not the presence of a long “nose” similar to an elephant’s trunk, but the ability to “see with its tail” (at least, this is what the locals believe). During the research, it was found that in the area of the “stern” of this fish there is a kind of natural generator, and in a special fin there is a sensory organ responsible for electroreception.

The electroreception organs of the water elephant are very sensitive: it is able to catch a grain of sand falling into the water. This allows him to successfully avoid fishing nets and other dangerous objects.

Interesting facts about fish

And now, as a dessert for publication, a few interesting facts about the sense organs of interesting representatives of ichthyofauna:

The world of fish is beautiful in its diversity. Let's try to make our grandchildren and great-grandchildren admire him!

Fish also have taste buds . Fish perfectly distinguishes bitter from sweet or salty. The taste perceptions of fish are different from the olfactory lobes of the brain! The taste buds of fish, which are sensitive cells, are located in the mouth (oral buds of the fish), on the lips, cheeks, mustache, as well as on the sides and head.

The fish has four nostrils in its nose, which are abundantly equipped with sensitive cells that perceive odors. Substances dissolved in water, entering the nostrils, irritate these cells, transmitting a signal to the brain about a particular smell. Water circulates freely through the cavities of the nostrils thanks to special valves located in them. At the same time, the sense of smell in different species of fish is developed differently. However, smell is usually much more important for fish than vision.

Fish also have taste buds . Fish perfectly distinguishes bitter from sweet or salty. The taste perceptions of fish are different from the olfactory lobes of the brain! The taste buds of fish, which are sensitive cells, are located in the mouth (oral buds of the fish), on the lips, cheeks, mustache, as well as on the sides and head.

A characteristic and very important sensory organ for fish is the lateral line (also present in aquatic amphibians). The lateral line is a kind of sensor for movements and vibrations of water. With its help, for example, predators perfectly sense the slightest movements of a potential victim, and the victim, on the contrary, senses a hidden predator. And also thanks to this “sensor”, fish navigate in the underwater space, avoid stationary obstacles, determine the location of food, the direction of the current, etc.

The lateral line is a channel passing through the entire body and communicating with water through holes in the scales. It contains very sensitive cells that respond to atmospheric pressure and inform the brain about its changes. This sensitive channel is also called the seismosensory organ. Sensitive organs that respond to pressure fluctuations in water are also found on the head, jaws and gill covers of fish. The lateral line is connected to the Central Nervous System by the vagus nerve.

The lateral line can be complete: it runs along the entire body of the fish; incomplete, and it may also be absent (for example, in herring). However, fish that lack a lateral line have other, well-developed channels of nerve endings. Damage to the lateral line of a fish can very quickly cause its death.

With their sense of smell they easily find food, relatives, and a partner for the spawning period. Some individuals are able to signal danger by releasing substances to which other fish are sensitive. It is believed that the sense of smell for aquatic inhabitants is more important than vision.

Digestive system of fish

The oral cavity of bony fishes contains undifferentiated teeth. Teeth can be located not only on the jaw bones, but also on the palatine bones and some other bones. Fish teeth perform only the functions of capturing and holding prey, but do not grind food. The fish simply swallow their food. They do not have salivary glands.

Following the oral cavity is the pharynx and esophagus, which opens into the stomach. Gastric juice contains hydrochloric acid and pepsin, which partially break down food. Further digestion occurs in the intestine with the help of secretions from the liver and pancreas. In herbivorous species of bony fish, the intestines are inhabited by symbiotic protozoa and bacteria that secrete enzymes that facilitate the digestion of food.

Baby fish feed on plankton. The food of adult bony fish is varied, many are omnivorous.

Electroreception

Electroreception is a sensory organ of cartilaginous fish and some bony fish (electric catfish). Sharks and rays sense electric fields using ampullae of Lorenzini - small capsules filled with mucous contents and lined with specific sensitive cells, located in the head area and communicate with the surface of the skin using a thin tube.

Very susceptible and capable of sensing weak electric fields (the reaction occurs at a voltage of 0.001 mKV/m).

Thus, electrosensitive fish can track down prey hidden in the sand thanks to the electric fields that are created when muscle fibers contract during breathing.

The lateral line and electrosensitivity are sensory organs characteristic only of fish!

Such a subtle sense of smell is developed in fish due to the fact that the olfactory bulb occupies a significant part of their brain.

It is generally accepted that since fish are at a lower level of organization than mammals, their sense organs are also more primitive. Actually this is not true!

Although their sensory experiences are different from ours, they are no less interesting and varied than those of higher vertebrates. And, of course, the full development of these organs is associated with the fish’s habitat – water.

Vision.

The importance of vision is not so great in aquatic inhabitants compared to terrestrial ones.

This is due, firstly , to the fact that with increasing depth, illumination decreases significantly, secondly , very often fish are forced to live in conditions of low water transparency, and thirdly , the aquatic environment allows them to use other senses with much greater efficiency.

Almost all fish have eyes located on both sides, which provides them with panoramic vision in the absence of a neck and, as a consequence, the impossibility of turning the head without turning the body. Low elasticity of the lens makes fish myopic and they cannot see clearly at long distances.

Many species have adapted their vision to highly specific living conditions: coral reef fish have not only color vision, but are also able to see in the ultraviolet spectrum; some fish that collect food from the surface of the water have eyes divided into two halves: the upper one sees what is happening in the air, the lower one - under water, in fish living in mountain caves, the eyes are generally reduced.

Hearing.

Oddly enough, fish have perfectly developed hearing , despite their lack of external signs. Their hearing organs are combined with the balance organs and are closed sacs with otoliths floating in them. Very often the swim bladder acts as a resonator. In a dense aquatic environment, sound vibrations travel faster than in air, so the importance of hearing for fish is great.

It is a well-known fact that fish in water hear the footsteps of a person walking along the shore.

Many fish are capable of making various purposeful sounds: rubbing their scales against each other, vibrating various parts of the body and thus carrying out sound communication.

Smell.

The sense of smell plays a significant role in the life of fish.

This is due to the fact that odors spread very well in water.

Everyone knows that a drop of blood falling into the water attracts the attention of sharks located several kilometers from this place.

In particular, salmon going to spawn use their sense of smell to find their way home.

Such a subtle sense of smell is developed in fish due to the fact that the olfactory bulb occupies a significant part of their brain.

Taste.

Flavoring substances are also perfectly distinguishable by fish , because... perfectly soluble in water. Taste buds are located not only in the mouth, but also throughout the rest of the body, especially on the head and antennae. For the most part, the taste organs are used by fish to search for food, as well as for orientation.

Touch.

Fish have ordinary mechanical receptors , which, like taste organs, are located mainly at the tips of their antennae, and are also scattered over the skin. However, in addition to this, fish have a completely unique receptor organ - the lateral line .

This organ, located along the middle on both sides of the body, is capable of perceiving the slightest fluctuations and changes in water pressure.

Thanks to the lateral line, fish can obtain information about the size, volume and distance to distant objects. With the help of the lateral line, fish are able to go around obstacles, avoid predators or find food, and maintain their position in the school.

Electrosensitivity.

Electrosensitivity is highly developed in many species of fish. It is an excellent addition to the already listed sense organs and allows fish to defend themselves, detect and obtain food, and navigate.

Some fish use electrolocation for communication, and thanks to the ability to sense the Earth's magnetic field, they can migrate over very long distances.

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In the course of their life, fish must perceive and analyze signals received from the external environment, and through these signals, if necessary, respond to changes in its parameters.

In the course of their life, fish must perceive and analyze signals received from the external environment, and through these signals, if necessary, respond to changes in its parameters.

Sea Fox Agonis

Photo by: Alexander Semenov

All external stimuli available for analysis by the sensory organs of fish can be divided into several types according to their nature. Fish can distinguish between chemical stimuli such as taste and smell, mechanical stimuli such as sound, touch, environmental vibrations, and also respond to electric and magnetic fields and, of course, light.

Below I will talk about what signals and what organs fish perceive, as well as the diversity of the external structure of these organs. This will be only the most general information - I will talk in detail about each of the sensory systems in separate posts.

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Skeleton

The skeleton is the support for well-developed striated muscles. Some muscle segments were partially rebuilt, forming muscle groups in the head, jaws, gill covers, pectoral fins, etc. (ocular, epibranchial and hypobranchial muscles, muscles of paired fins).

swim bladder

Above the intestines is a thin-walled sac - a swim bladder, filled with a mixture of oxygen, nitrogen and carbon dioxide. The bladder formed from an outgrowth of the intestine. The main function of the swim bladder is hydrostatic. By changing the pressure of gases in the swim bladder, the fish can change the depth of its dive.

If the volume of the swim bladder does not change, the fish is at the same depth, as if hanging in the water column. When the volume of the bubble increases, the fish rises. When lowering, the reverse process occurs. The swim bladder of some fish can participate in gas exchange (as an additional respiratory organ), serve as a resonator when producing various sounds, etc.

Skin of fish

The outer integument of fish is represented by the epidermis and connective dermis. The epidermis contains glands that produce mucus, designed to reduce friction of the body against the water column during the movement of the individual.

Bone scales are the main feature that distinguishes bony fish from cartilaginous fish, which have placoid-type scales.

The skin contains pigment cells that form the color of the body. Some individuals can change the tone of their body in the process of development and adaptation to external conditions.

The structure of the skin of fish

The structure of fins and their functions

There are two groups of fins in fish. The first is represented by paired elements located on the peritoneum and chest. The second group is formed by unpaired fins located on the dorsal part, tail, near the anal exit. The abdominal and thoracic elements are stabilizers. When an individual is at rest, they help maintain balance. The caudal fin has the function of a “steering fin”. It provides a force that pushes it forward.

How do fish reproduce?

Males have gonads shaped like paired white seminal cavities. Females have formed ovaries. In representatives of the bony class of fish, the process of fertilization occurs externally; there are also exceptions to the general rules.

Some species are fertilized internally. In male representatives of this category, the fins at the anus are transformed into a sexual organ - gonopodium, which promotes internal insemination.

In most cases, the insemination process is carried out externally. When the time comes to create offspring, the female spawns eggs outside. At the next stage, the male begins to fertilize the eggs using the released seminal fluid. After a certain time, small larvae begin to hatch from the eggs, feeding initially from the yolk sac. The larvae develop into fry, which then grow into full-fledged individuals.

Reproductive system of fish

The fertility rate ranges from several tens to 1 million eggs, depending on the species. For example, the sunfish is capable of laying up to 28 million eggs. Of the samples obtained, only a few specimens survive. Caviar is heavier than water, so it is deposited on the bottom and aquatic plants.

Most fish begin to spawn under strictly defined conditions, characteristic of each individual species. In order to lay eggs, individuals gather in places with a certain water temperature, degree of salinity, aeration, and alkalinity indicators. Eggs and hatched larvae are more susceptible to environmental conditions than adults. That is why spawning in compliance with all environmental factors contributes to greater productivity and survival of the larvae.

Individuals in their natural habitat rush to spawn in local places and conditions suitable for the development of eggs and the concentration of the required number of producers. These actions also help to isolate themselves from other representatives of the aquatic world and preserve their offspring.

Share your discoveries in the structure of fish in the comments!

Circulatory system of fish

The heart of fish is two-chambered (one atrium and one ventricle), therefore, there is only one circle of blood circulation. Venous blood passes through the heart, which then goes to the gills. From there, arterial blood enters the dorsal aorta through the efferent gill arteries and is distributed throughout the tissues through the vessels extending from it. Having given up oxygen, the blood flows through the veins into the atrium.

Thus, the afferent branchial arteries deliver venous blood from the heart, and the efferent branchial arteries with arterial blood unite into the dorsal aorta.

The heart of fish contracts rarely and weakly. So in river perch 20 contractions occur per minute. Consequently, fish have a rather slow metabolism. Fish are cold-blooded (their body temperature depends on the ambient temperature).

Features of sensory organs in bony and cartilaginous

Inert fish have a swim bladder, which perceives a wider range of sounds; cartilaginous fish do not have it, and they also do not have a complete division of the inner ear into oval and round sacs.

Color vision is characteristic of teleosts, since their retina contains both rods and cones. The cartilaginous visual sensory organ includes only rods that are not capable of distinguishing colors.

Sharks have a very keen sense of smell; the anterior part of the brain (provides the sense of smell) is much more developed than other representatives.

Electrical organs are special organs of cartilaginous fish (rays). They are used for protection and attack on the victim, and discharges with a power of up to 600V are generated. They can act as a sensory organ - by forming an electric field, stingrays detect changes when foreign bodies enter it.

Chemical reception organs serve to obtain information about substances dissolved in water and the taste of food. They include: 1) olfactory organs; 2) organs of chemical non-olfactory reception.

The organs of smell (olfactory sacs) are located in the nasal cavity. Fish usually have paired nasal openings (nostrils). The nostril is divided by a leathery valve and has two openings; water enters the olfactory sac through the anterior opening and exits through the posterior one. The cavity of the olfactory sac has folds (rosettes) and is lined with mucous membrane associated with nerve endings. The olfactory nerves coming from the forebrain and the fibers of the trigeminal nerve approach the olfactory organs.

Cyclostomes have an unpaired olfactory organ (in hagfishes it communicates with the pharynx, in lampreys it does not). In lampreys, the nostril leads into a long canal, the posterior wall of which forms an olfactory capsule with sensory cells. The canal continues to the beginning of the notochord, forming a pituitary process. The pituitary gland is adjacent to the upper part of this outgrowth. The olfactory canal of lampreys is also called the nasopituitary canal. The movement of water (taking it in and pushing it back) in the olfactory capsule is carried out by changing the volume of the pituitary outgrowth. In hagfishes, the pituitary process opens with an opening into the oral cavity, so in a hagfish buried in the mud, water can flow to the gill sacs through the nostrils.

Fish have paired olfactory organs. In cartilaginous fish, paired nostrils are usually located on the ventral side of the snout. In all fish (with the exception of lungfishes and lobe-finned fish), the nostrils do not communicate with the pharyngeal cavity.

With the help of the olfactory organs, fish find food, distinguish gender, the physiological state of fish, and orient themselves in space. Some species are very sensitive to odors (sharks, anadromous salmon, burbot, eel, etc.). Thus, sharks are able to recognize the smell of blood at a distance of up to 2 km.

Fish are sensitive to danger signals and to substances released from the skin when injured. The reaction of fish is different: some bury themselves in the mud, others hide, others jump out of the water, etc. The olfactory organs play an important role during fish migrations. Thus, salmon fish remember the smell (chemical composition) of the river in which they hatched from eggs, and several years after feeding in the sea, they return to reproduce in their native reservoir (the phenomenon of homing - finding a home). Experiments with tagging of larvae showed that out of 13 thousand fish caught at spawning grounds, 34% entered exactly the rivers and streams where they hatched from eggs, 65% into neighboring ones, and only 1% were caught at a considerable distance from the tagging sites.

The organs of chemical non-olfactory reception perceive various chemical indicators of the environment (salinity, active reaction of the environment, carbon dioxide concentration, etc.) and are represented by: 1) taste buds (a cluster of sensory cells); 2) taste cells (ball-shaped, bush-shaped, fusiform); 3) free nerve endings.

In fish, the center of chemical non-olfactory reception is located in the medulla oblongata.

Taste buds and cells are located mainly in the oral mucosa, on the antennae, gills, head, and fin rays. Pisces distinguish shades of taste (sweet, bitter, salty, sour). The pungency of taste is associated with the ecological characteristics of the species (food specialization, type of habitat, degree of development of other receptors). Thus, the blind Mexican cave fish recognizes a glucose solution at a concentration of 0.005%.

Pisces are able to perceive tactile (touch, pressure), pain, and temperature sensations. Tactile sensations are perceived through the senses of touch. These include tactile corpuscles (a cluster of sensory cells) scattered over the surface of the body. Many tactile points are located on the head, antennae and fins of the fish. Pisces have low pain sensitivity due to the low level of development of the nervous system.

Fish are very sensitive to temperature changes. Water temperature is perceived by fish using thermoreceptors (free nerve endings) located in the surface layers of the skin. Small deviations in water temperature can change the migration routes and timing of fish spawning. Bony fish are able to distinguish between temperature differences of 0.4°C.

N.V. ILMAST. INTRODUCTION TO ICHTHYOLOGY. Petrozavodsk, 2005

Smell and taste The olfactory organ is formed by a pair of small nasal pits, which are lined with olfactory epithelium. The olfactory organ of fish perceives chemical irritants from substances dissolved in water. The sense of smell is especially developed in fish that search for food at night - carp, eel and bream. Fish have a well-developed taste organ. They distinguish between salty, sour, sweet and bitter tastes. Taste buds are found in the mouth, along the edges of the jaws and on the antennae. Fish that lack antennae have a poorly developed taste. From the point of view of fly fishing and spinning, this sense organ is not important. The main components of taste are four components: sour, sweet, salty and bitter. The remaining types of taste are combinations of these four sensations, and taste sensations in fish can only be caused by substances dissolved in water. The minimal perceptible difference in the concentration of solutions of substances is the threshold of difference - gradually worsens when moving from weak to stronger concentrations. For example, a one percent sugar solution has an almost maximally sweet taste, and a further increase in its concentration does not change the taste sensation.

With prolonged contact of any substance with the organ of taste, its perception gradually becomes dulled, and in the end this substance will seem completely tasteless to the fish. Positive or negative reactions of fish are determined by their lifestyle and, above all, the nature of their diet. Positive reactions to sugar are characteristic of animals eating plant and mixed foods. The feeling of bitterness causes a negative reaction in most living beings, but not in those that eat insects. The sense of smell is closely connected with other senses: taste, vision and balance. At different times of the year, the olfactory sensations of fish are not the same; they become more intense in spring and summer, especially in warm weather. Extracts from the internal organs of predators - pike, swimming swimmers, water striders, and water bugs - repel roach and crucian carp. According to many scientists, animals are guided by a mixture of basic odors: musky, camphor, mint, ethereal, floral, pungent and rotten. These odors make up all the odors found in nature. You should not keep wounded fish in a cage while fishing or cut them in the water at the fishing site (especially predatory fish).

Hearing organs The auditory function in fish is carried out, according to experts, in addition to the main organ of hearing, the lateral line, the swim bladder, as well as specific nerve endings. Anatomically, like all vertebrates, the main organ of hearing, the ear, is a paired organ and forms a single whole with the organ of balance. The only difference is that fish do not have ears and eardrums, since they live in a different environment. The hearing organs of fish developed in an aquatic environment, which conducts sound 4 times faster and over longer distances than the atmosphere. The range of sound perception in fish is much wider than in many land animals and people. In the lateral line of the fish, formations were discovered that record acoustic and other water vibrations. It has been established that fish are able to detect 10 times less frequency changes than humans. The swim bladder is believed to act as a resonator and transducer of sound waves, which increases hearing acuity. It also performs a sound-producing function. Paired organs located in the lateral line of fish perceive sound vibrations in a panoramic manner, which allows fish to clearly establish the direction and location of the source of vibration. Fish distinguish near and far zones of the acoustic field. In the near field, they clearly determine the location of the source of the vibration, but scientists have not yet determined whether they can determine the location of the source in the far field. Pisces also have an amazing “device” - a signal analyzer. Thanks to this organ, fish are able to isolate from all the chaos of sounds and vibrational manifestations around them the signals that are necessary and important for them, even those weak ones that are at the stage of emerging or on the verge of fading. Fish are able to amplify these weak signals and then perceive them with analyzing formations. Fish widely use sound signaling; they are capable of both perceiving and emitting sounds in a wide range of frequencies. I would like to draw the readers’ attention to the perception of infrasonic vibrations by fish, which, in my opinion, is of great importance in the life of fish. It is believed that frequencies equal to 4-6 hertz have a detrimental effect on living organisms, since these vibrations resonate with the vibrations of the body itself or individual organs and destroy them. It is possible that fish react to the approach of inclement weather by perceiving low-frequency acoustic vibrations emanating from approaching cyclones. On this basis, it can be assumed that fish are able to predict weather changes long before they occur; fish detect these changes by the difference in the strength of sounds, and possibly by the level of interference for the passage of waves of a certain range. There is evidence that fish are capable of echolocation.

Location sensitivity organs of fish No one doubts that fish use location in their lives. Radar and sonar, integral components of this organ, were found in the lateral line of the fish. It is possible that fish use low-frequency waves of a wide range for location. It is believed that these waves serve fish for communication purposes. Hydroacoustic studies have shown that fish are too “chatty” for an unreasonable creature; they produce too many sounds, and “conversations” are conducted at frequencies that are beyond the normal range of perception by their primary organ of hearing. It is unlikely that this “chattyness” has only a communication value; this conversation would be too attractive for predators. These signals are more appropriate as location signals sent by fish radars. It is believed that low-frequency waves are poorly reflected (badly, but not completely!) from small objects, since due to their length they simply flow around objects. But these waves have a number of advantages over ultrashort ones: they are less absorbed by water, are heard over long distances, propagate evenly in all directions from the sound source, their use for location makes it possible to panoramic “seeing and hearing” the surrounding space. And if fish, for location purposes, send a whole series of signals of different frequencies, then a panoramic survey is guaranteed. This will also help compensate for the lack of reflected signals. Considering the high sensitivity of fish’s sensory organs, it can be assumed that they can use these reflected signals. I hope that the above confirms that location occurs in fish and we should agree with the existence of an organ of location sensitivity. This is an independent organ, and despite the fact that sound waves are used for its operation, it cannot be classified as an organ of hearing. This is an important sensory organ for the life of fish. It remains to be found out what frequencies fish use for location?

We continue our traditional column Tips from experienced fishermen - we’ll tell you about the sensory organs of fish:

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