Can an electric fish? Are fish attracted to electric and magnetic fields - What does the bite depend on?

Speaking about the possibility of fish using the Earth’s magnetic field for navigation purposes, it is natural to raise the question of whether they can perceive this field at all.

In principle, both specialized and non-specialized systems can respond to the Earth’s magnetic field. At present, it has not been proven that fish have specialized receptors sensitive to this field.

How do non-specialized systems perceive the Earth's magnetic field? More than 40 years ago, it was suggested that the basis of such mechanisms could be induction currents arising in the body of fish when they move in the Earth's magnetic field. Some researchers believed that during migrations fish use electric induction currents resulting from the movement (flow) of water in the Earth's magnetic field. Others believed that some deep-sea fish use inductive currents that arise in their bodies when moving.

It is calculated that at a fish movement speed of 1 cm per second per 1 cm of body length, a potential difference of about 0.2-0.5 μV is established. Many electric fish, which have special electroreceptors, perceive electric field strengths of even lower magnitude (0.1-0.01 μV per 1 cm). Thus, in principle, they can be oriented towards the Earth’s magnetic field during active movement or passive drift (drift) in water flows.

Analyzing the graph of the threshold sensitivity of the gymnarch, the Soviet scientist A. R. Sakayan concluded that this fish senses the amount of electricity flowing in its body, and suggested that weakly electric fish are able to determine the direction of their path along the Earth’s magnetic field.

Sakayan views fish as a closed electrical circuit. When a fish moves in the Earth's magnetic field, an electric current passes through its body as a result of induction in the vertical direction. The amount of electricity in the body of a fish when it moves depends only on the relative position in space of the direction of the path and the line of the horizontal component of the Earth's magnetic field. Therefore, if a fish responds to the amount of electricity flowing through its body, it can determine its path and its direction in the Earth's magnetic field.

Thus, although the question of the electro-navigation mechanism of weakly electric fish has not yet been fully clarified, the fundamental possibility of their use of induction currents is beyond doubt.

The vast majority of electric fish are “sedentary”, non-migrant forms. In migrant non-electric fish species (cod, herring, etc.), electrical receptors and high sensitivity to electric fields have not been found: usually it does not exceed 10 mV per 1 cm, which is 20,000 times lower than the intensity of electric fields caused by induction. The exception is non-electric fish (sharks, rays, etc.), which have special electroreceptors. When moving at a speed of 1 m/s, they can perceive an induced electric field of 0.2 μV per 1 cm. Electric fish are approximately 10,000 times more sensitive to electric fields than non-electric fish. This suggests that non-electric fish species cannot navigate the Earth's magnetic field using induction currents. Let us dwell on the possibility of fish using bioelectric fields during migration.

Almost all typically migratory fish are schooling species (herring, cod, etc.). The only exception is the eel, but when entering the migratory state, it undergoes a complex metamorphosis, which may affect the generated electric fields.

During the migration period, fish form dense, organized schools moving in a certain direction. Small schools of these same fish cannot determine the direction of migration.

Why do fish migrate in schools? Some researchers explain this by the fact that, according to the laws of hydrodynamics, the movement of fish in schools of a certain configuration is facilitated. However, there is another side to this phenomenon. As already mentioned, in excited schools of fish the bioelectric fields of individual individuals are summed up. Depending on the number of fish, the degree of their excitation and the synchronicity of the radiation, the total electric field can significantly exceed the volumetric dimensions of the school itself. In such cases, the voltage per fish can reach such a value that it is able to perceive the electric field of the school even in the absence of electroreceptors. Consequently, fish can use the school's electric field for navigation purposes due to its interaction with the Earth's magnetic field.

How do non-schooling migrant fish, such as eels and Pacific salmon, which make long migrations, navigate in the ocean? The European eel, for example, becoming sexually mature, moves from rivers to the Baltic Sea, then to the North Sea, enters the Gulf Stream, moves against the current in it, crosses the Atlantic Ocean and comes to the Sargasso Sea, where it breeds at great depths. Consequently, the eel cannot navigate either by the Sun or by the stars (birds use them to navigate during migrations). Naturally, the assumption arises that since the eel travels most of its journey while in the Gulf Stream, it uses the current for orientation.

Let's try to imagine how an eel orients itself while inside a multi-kilometer layer of moving water (chemical orientation is excluded in this case). In the water column, all the streams of which move in parallel (such flows are called laminar), the eel moves in the same direction as the water. Under these conditions, its lateral line - an organ that allows it to perceive local water flows and pressure fields - cannot work. In the same way, when floating along a river, a person does not feel its flow if he does not look at the shore.

Perhaps the sea current does not play any role in the eel’s orientation mechanism and its migration routes coincidentally coincide with the Gulf Stream? If so, then what environmental signals does the eel use and what guides it when oriented?

It remains to be assumed that eel and Pacific salmon use the Earth's magnetic field in their orientation mechanism. However, no specialized systems for its perception have been found in fish. But in the course of experiments to determine the sensitivity of fish to magnetic fields, it turned out that both eels and Pacific salmon have exceptionally high sensitivity to electric currents in water directed perpendicular to the axis of their body. Thus, the sensitivity of Pacific salmon to current density is 0.15 * 10 -2 μA per 1 cm 2, and the sensitivity of eels is 0.167 * 10 -2 per 1 cm 2.

The idea was expressed that eels and Pacific salmon use geoelectric currents created in ocean water by currents. Water is a conductor moving in the Earth's magnetic field. The electromotive force resulting from induction is directly proportional to the strength of the Earth's magnetic field at a given point in the ocean and a certain current speed.

A group of American scientists carried out instrumental measurements and calculations of the magnitudes of emerging geoelectric currents along the eel’s route. It turned out that the densities of geoelectric currents are 0.0175 μA per 1 cm 2, i.e., almost 10 times higher than the sensitivity of migrant fish to them. Subsequent experiments confirmed that eels and Pacific salmon are selective towards currents with similar densities. It became obvious that eel and Pacific salmon can use the Earth's magnetic field and sea currents for their orientation during migrations in the ocean due to the perception of geoelectric currents.

The Soviet scientist A.T. Mironov suggested that when orienting fish, they use telluric currents, which he first discovered in 1934. Mironov explains the mechanism of occurrence of these currents by geophysical processes. Academician V.V. Shuleikin connects them with electromagnetic fields in space.

Currently, the work of employees of the Institute of Terrestrial Magnetism and Radio Wave Propagation in the Ionosphere of the USSR Academy of Sciences has established that the constant component of the fields generated by telluric currents does not exceed a strength of 1 µV per 1 m.

Soviet scientist I. I. Rokityansky suggested that since telluric fields are inductive fields with different amplitudes, periods and directions of vectors, fish tend to go to places where the magnitude of telluric currents is less. If this assumption is correct, then during the period of magnetic storms, when the intensity of telluric fields reaches tens - hundreds of microvolts per meter, fish should move away from the shores and from shallow places, and, consequently, from fishing grounds to deep-sea areas, where the magnitude of telluric fields is less. Studying the relationship between fish behavior and magnetic activity will make it possible to develop methods for predicting their fishing aggregations in certain areas. Employees of the Institute of Terrestrial Magnetism and Radio Wave Propagation in the Ionosphere and the Institute of Evolutionary Morphology and Animal Ecology of the USSR Academy of Sciences carried out work in which a certain correlation was identified when comparing Norwegian herring catches with magnetic storms. However, all this requires experimental verification.

As mentioned above, fish have six signaling systems. But don’t they use some other sense that is not yet known?

In the USA in the newspaper “Electronics News” for 1965 and 1966. a message was published about the discovery by W. Minto of special “hydronic” signals of a new nature, used by fish for communication and location; Moreover, in some fish they were recorded at a great distance (in mackerel up to 914 m). It was emphasized that “hydronic” radiation cannot be explained by electric fields, radio waves, sound signals or other previously known phenomena: hydronic waves propagate only in water, their frequency ranges from fractions of a hertz to tens of megahertz.

It was reported that the signals were discovered by studying the sounds made by fish. Among them are frequency-modulated, used for location, and amplitude-modulated, emitted by most fish and intended for communication. The former resemble a short whistle, or “chirp,” while the latter resemble a “chirp.”

W. Minto and J. Hudson reported that hydronic radiation is characteristic of almost all species, but this ability is especially strongly developed in predators, fish with underdeveloped eyes and in those that hunt at night. Fish emit orientation signals (location signals) in a new environment or when exploring unfamiliar objects. Communication signals are observed in a group of individuals after the return of fish that have been in an unfamiliar environment.

What prompted Minto and Hudson to consider “hydronic” signals to be a manifestation of a previously unknown physical phenomenon? According to them, these signals are not acoustic because they can be perceived directly by the electrodes. At the same time, “hydronic” signals cannot be classified as electromagnetic oscillations, according to Minto and Hudson, since, unlike ordinary electrical ones, they consist of pulses that are not constant and last several milliseconds.

However, it is difficult to agree with such views. In electric and non-electric fish, signals are very diverse in shape, amplitude, frequency and duration, and therefore the same properties of “hydronic” signals do not indicate their special nature.

The last “unusual” feature of “hydronic” signals - their propagation over a distance of 1000 m - can also be explained on the basis of well-known principles of physics. Minto and Hudson did not conduct laboratory experiments on a single individual (data from such experiments indicate that the signals of individual non-electric fish travel over short distances). They recorded signals from schools and schools of fish in marine conditions. But, as already mentioned, in such conditions the intensity of the bioelectric fields of fish can be summed up, and the single electric field of the school can be detected at a considerable distance.

Based on the above, we can conclude that in the works of Minto and Hudson it is necessary to distinguish between two sides: the factual one, from which it follows that non-electric fish species are capable of generating electrical signals, and the “theoretical” - an unproven assertion that these discharges have a special, so-called hydronic nature.

In 1968, the Soviet scientist G. A. Ostroumov, without going into the biological mechanisms of generation and reception of electromagnetic signals by marine animals, but based on the fundamental principles of physics, made theoretical calculations that led him to the conclusion that Minto and his followers were mistaken in attributing special physical nature of “hydronic” signals. In essence, these are ordinary electromagnetic processes.

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Occur, for example, in many plants. But the most amazing carrier of this ability are electric fish. Their gift of producing powerful discharges is not available to any other animal species.

Why do fish need electricity?

The ancient inhabitants of the sea coasts knew that some fish can strongly “beat” the person or animal that touched them. The Romans believed that at this moment the inhabitants of the depths released some kind of strong poison, as a result of which the victim experienced temporary paralysis. And only with the development of science and technology it became clear that fish tend to create electrical discharges of varying strengths.

Which fish is electric? Scientists claim that these abilities are characteristic of almost all representatives of the named species of fauna, it’s just that in most of them the discharges are small, perceptible only with powerful sensitive devices. They use them to transmit signals to each other - as a means of communication. The strength of the emitted signals allows you to determine who is who in the fish environment, or, in other words, find out the strength of your opponent.

Electric fish use their special organs to protect themselves from enemies, as weapons to kill prey, and also as locators.

Where is the fish's power plant?

Electrical phenomena in the body of fish have interested scientists involved in natural energy phenomena. The first experiments to study biological electricity were carried out by Faraday. For his experiments, he used stingrays as the most powerful producers of charges.

One thing that all researchers agreed on is that the main role in electrogenesis belongs to cell membranes, which are capable of distributing positive and negative ions in cells, depending on excitation. The modified muscles are connected to each other in series, these are the so-called power plants, and the connective tissues are conductors.

“Energy-producing” bodies can have very different types and locations. So, in stingrays and eels these are kidney-shaped formations on the sides, in elephant fish they are cylindrical threads in the tail area.

As already mentioned, producing current on one scale or another is common to many representatives of this class, but there are real electric fish that are dangerous not only to other animals, but also to humans.

Electric snake fish

The South American electric eel has nothing in common with ordinary eels. It is named simply because of its external resemblance. This long, up to 3 meters, snake-like fish weighing up to 40 kg is capable of generating a discharge of 600 volts! Close communication with such a fish can cost your life. Even if the current does not directly cause death, it will definitely lead to loss of consciousness. A helpless person can choke and drown.

Electric eels live in the Amazon, in many shallow rivers. The local population, knowing their abilities, does not enter the water. The electric field produced by the snake fish diverges over a radius of 3 meters. At the same time, the eel shows aggression and can attack without any particular need. He probably does this out of fear, since his main diet is small fish. In this regard, a living “electric fishing rod” does not know any problems: release the charger, and breakfast is ready, lunch and dinner at the same time.

Stingray family

Electric fish - stingrays - are grouped into three families and number about forty species. They tend not only to generate electricity, but also to accumulate it in order to use it further for its intended purpose.

The main purpose of the shots is to scare away enemies and catch small fish for food. If a stingray releases its entire accumulated charge at one time, its power will be enough to kill or immobilize a large animal. But this happens extremely rarely, since the fish - the electric stingray - after a complete “blackout” becomes weak and vulnerable, it takes time for it to accumulate power again. So stingrays strictly control their energy supply system with the help of one of the parts of the brain, which acts as a relay switch.

The family of stingrays, or electric stingrays, are also called “torpedoes.” The largest of them is the inhabitant of the Atlantic Ocean, the black torpedo (Torpedo nobiliana). This one, which reaches a length of 180 cm, produces the strongest current. And in close contact with it, a person may lose consciousness.

Moresby's ray and Tokyo torpedo (Torpedo tokionis ) - the deepest representatives of their family. They can be found at a depth of 1,000 m. And the smallest among its fellows is the Indian stingray, its maximum length is only 13 cm. A blind stingray lives off the coast of New Zealand - its eyes are completely hidden under a layer of skin.

Electric catfish

In the muddy waters of tropical and subtropical Africa live electric fish - catfish. These are quite large individuals, from 1 to 3 m in length. Catfish do not like fast currents; they live in cozy nests at the bottom of reservoirs. The electrical organs, which are located on the sides of the fish, are capable of producing a voltage of 350 V.

The sedentary and apathetic catfish does not like to swim far from its home; it crawls out of it to hunt at night, but it also does not like uninvited guests. He meets them with light electric waves, and with them he gets his prey. Discharges help catfish not only hunt, but also navigate in dark, muddy water. Electric catfish meat is considered a delicacy among the local African population.

Nile dragon

Another African electric representative of the kingdom of fish is the Nile gymnarch, or aba-aba. The pharaohs depicted him in their frescoes. It lives not only in the Nile, but in the waters of the Congo, Niger and some lakes. This is a beautiful “stylish” fish with a long graceful body, from forty centimeters to one and a half meters long. There are no lower fins, but one upper one stretches along the entire body. Underneath it is a “battery” that produces electromagnetic waves of 25 V almost constantly. The head of the gymnarch carries a positive charge, and the tail carries a negative charge.

Gymnarchs use their electrical abilities not only to search for food and location, but also in mating games. By the way, male gymnarchs are simply amazingly fanatical fathers. They do not move away from laying eggs. And as soon as someone gets close to the children, dad will shower the offender with a stun gun so much that it won’t seem like much.

Gymnarchs are very cute - their elongated, dragon-like muzzle and cunning eyes have gained love among aquarists. True, the handsome guy is quite aggressive. Of several fry placed in an aquarium, only one will survive.

Sea cow

Large bulging eyes, an ever-open mouth framed by fringe, and an extended jaw make the fish look like an eternally dissatisfied, grumpy old woman. What is the name of an electric fish with such a portrait? family of stargazers. The comparison with a cow is evoked by the two horns on its head.

This unpleasant individual spends most of its time buried in the sand and lies in wait for prey passing by. The enemy will not pass: the cow is armed, as they say, to the teeth. The first line of attack is a long red tongue-worm, with which the stargazer lures naive fish and catches them without even getting out of cover. But if necessary, it will fly up instantly and stun the victim until he loses consciousness. The second weapon for self-defense is poisonous spines located behind the eyes and above the fins. And that is not all! The third powerful weapon is located behind the head - electrical organs that generate charges with a voltage of 50 V.

Who else is electric?

The ones described above are not the only electric fish. The names of those not listed by us sound like this: Peters gnathonema, black knifeworm, mormyra, diplobatis. As you can see, there are a lot of them. Science has made a big step forward in studying this strange ability of some fish, but to this day it has not been possible to completely unravel the mechanism for accumulating high-power electricity.

Do fish heal?

Official medicine has not confirmed that the electromagnetic field of fish has a healing effect. But folk medicine has long used the electric waves of stingrays to cure many diseases of a rheumatic nature. To do this, people specifically walk nearby and receive weak shocks. This is what natural electrophoresis looks like.

Residents of Africa and Egypt use electric catfish to treat severe fever. To increase immunity in children and strengthen their general condition, equatorial residents force them to touch catfish, and also give them water in which this fish swam for some time.

IT TURNS out that electricity is not only generated by people!

Among electric fish, the lead belongs to the electric eel, which lives in the tributaries of the Amazon and other rivers of South America. Adult eels reach two and a half meters. Electrical organs - transformed muscles - are located on the sides of the eel, extending along the spine for 80 percent of the entire length of the fish. This is a kind of battery, the plus of which is in the front of the body, and the minus is in the back. A living battery produces a voltage of about 350, and in the largest individuals - up to 650 volts. With an instantaneous current of up to 1-2 amperes, such a discharge can knock a person off his feet. With the help of electrical discharges, the eel protects itself from enemies and obtains food for itself.

Another fish lives in the rivers of Equatorial Africa - the electric catfish. Its dimensions are smaller - from 60 to 100 cm. Special glands that generate electricity make up about 25 percent of the total weight of the fish. The electric current reaches a voltage of 360 volts. There are known cases of electric shock in people who swam in the river and accidentally stepped on such a catfish. If an electric catfish is caught on a fishing rod, then the angler can also receive a very noticeable electric shock that passes through the wet fishing line and rod to his hand.

However, skillfully directed electrical discharges can be used for medicinal purposes. It is known that the electric catfish occupied an honorable place in the arsenal of traditional medicine among the ancient Egyptians.

Electric stingrays are also capable of generating very significant electrical energy. There are more than 30 species. These sedentary bottom dwellers, ranging in size from 15 to 180 cm, are distributed mainly in the coastal zone of tropical and subtropical waters of all oceans. Hiding at the bottom, sometimes half-immersed in sand or silt, they paralyze their prey (other fish) with a discharge of current, the voltage of which in different species of stingrays ranges from 8 to 220 volts. A stingray can cause a significant electric shock to a person who accidentally comes into contact with it.

In addition to high-power electrical charges, fish are also capable of generating low-voltage, weak current. Thanks to rhythmic discharges of weak current with a frequency of 1 to 2000 pulses per second, they perfectly navigate even in turbid water and signal each other about emerging danger. Such are the mormirus and gymnarchs, who live in the muddy waters of rivers, lakes and swamps in Africa.

In general, as experimental studies have shown, almost all fish, both marine and freshwater, are capable of emitting very weak electrical discharges, which can only be detected with the help of special devices. These discharges play an important role in the behavioral reactions of fish, especially those that constantly stay in large schools.

From the magazine “Science and Life”№3, 1998 G.

The electric eel is a large fish, 1 to 3 meters long, the eel weighs up to 40 kg. The body of the eel is elongated - serpentine, covered with gray-green skin without scales, and in the front part it is rounded, and closer to the tail it is flattened laterally. Eels live in South America, in particular in the Amazon River basin.

A large eel creates a discharge with a voltage of up to 1200 V and a current of up to 1 A. Even small aquarium specimens produce discharges from 300 to 650 V. Thus, an electric eel can pose a serious danger to humans.

The electric eel accumulates significant charges of electricity, the discharges of which are used for hunting and defense against predators. But the eel is not the only fish that produces electricity.

Electric fish

In addition to electric eels, a huge number of freshwater and saltwater fish are capable of generating electricity. In total there are about three hundred such species from various unrelated families.

Most "electric" fish use an electric field to navigate or find prey, but some representatives have more serious charges.

Electric rays are cartilaginous fish, relatives of sharks; depending on the species, they can have a charge voltage of 50 to 200 V, and the current reaches 30 A. Such a charge can hit quite large prey.

Electric catfish are freshwater fish, reaching 1 meter in length and weighing no more than 25 kg. Despite its relatively modest size, the electric catfish is capable of producing 350-450 V, with a current of 0.1-0.5 A.

Electric organs

These fish exhibit unusual abilities thanks to modified muscles - an electrical organ. In different fish, this formation has a different structure, size, and location; for example, in the electric eel it is located on both sides along the body and makes up about 25% of the fish’s mass.

At the Enoshima Aquarium in Japan, an electric eel is used to light up the Christmas tree. The tree is connected to an aquarium, the fish living in it produces about 800 W of electricity, which is quite enough for illumination.

Any electrical organ consists of electrical plates - modified nerve and muscle cells, the membranes of which create a potential difference.

Electric plates connected in series are assembled into columns that are connected in parallel to each other. The potential difference generated by the plates accumulates at opposite ends of the electrical organ. All that remains is to activate it.

An electric eel, for example, bends and a series of electrical discharges jump between the positively charged front of the body and the negatively charged back, striking the prey.

The potential difference at the ends of the electrical organs can reach 1200 volts, and the discharge power per pulse can range from 1 to 6 kilowatts. The frequency of the pulses depends on their purpose. For example, an electric stingray emits 10-12 pulses when defending itself, and from 14 to 562 when attacking. The voltage power in the discharge varies from 20 to 600 volts in different fish. Among marine fish, the most powerful electrical organ is the ray Torpedo maromata - it can generate a discharge of more than 200 volts. Electricity protects it from both sharks and octopuses, and also allows it to hunt small fish.

In freshwater fish the discharges are even more powerful. The fact is that salt water conducts electricity better than fresh water. Therefore, sea fish require less energy to stun the enemy. One of the most dangerous freshwater fish is the electric eel from the Amazon. There are three electrical organs on his body. Two of them are for navigation and searching for prey, and the third is a powerful weapon with a voltage of more than 500 volts. An electric shock of this magnitude not only kills fish and frogs, but can even cause serious harm to humans. Therefore, catching Amazon eels is very dangerous. To do this, a herd of cows is driven into the river so that the eels spend all their energy on them. Only after this do people enter the water.

Some fish use electricity to navigate. For example, the Nile elephant or knife fish create an electromagnetic field around themselves. When a foreign object hits it, the fish immediately senses it. This navigation system resembles the echolocation of bats. It allows you to navigate well in muddy water. Studies have shown that many electric fish are so sensitive to changes in electromagnetic fields that they are able to “anticipate” an approaching earthquake.