Rescue Repeller
The United States was the first country to seriously develop shark repellent in the mid-20th century. These attempts were in no way connected with the desire to protect swimmers, but were carried out on the initiative of the military. During the Second World War, the main conflicts between the USA and Japan took place at sea or on the islands, and naval aviation was the main strike force at that time. If the pilot of the crashed plane is lucky, he can jump out of the cockpit and fall into the water. Life jackets made it possible to wait for a rescue team for hours and sometimes days, but only if the person did not attract sharks. Downed pilots often died from the attacks of these fish, and since trained flight personnel was the most expensive asset of combat aviation, after the war the Americans began to develop a propellant.
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“Special naval laboratories with all island bases were created, instructed to conduct experiments and find substances that could scare sharks from a potential victim. However, despite the huge budget and years of effort, it was not possible to create a working vehicle. Things Americans don’t try – from the simplest irritants to chemical warfare agents. They even remembered old racist myths that sharks don’t like the smell of blacks. We tried the smell of urine, the smell of sweat – nothing worked. Of course, if you poison the water with chemical weapons, the shark will die, but in this case, the person will also be harmed,” he said. – said Alexander Kasumyan, Doctor of Biological Sciences, Professor of the Faculty of Biology at Moscow State University. Lomonosov and head of the ichthyology department.
Subsequent attempts to create chemical protection against sharks were made in the 70s of the XX century. Later, ichthyologists discovered small flounder-like fish that, in the course of evolution, learned to secrete a repellent against sharks. These “tongues of the sea” Pardachirus marmoratusthey do not have a well-known Russian name, as they live in the tropics.
“The secret secreted by the glands of these fish turned out to be an effective repellent, including in field tests. However, scientists have not been able to find out exactly which component of this secret, which is the active substance, causes a rejection reaction or even “runaway”. These substances, which could be isolated, worked so poorly that hypotheses arose that only a mixture of certain compounds could possibly act in strict proportions. Some experts concluded that the active substance is very complex and high molecular, most likely a protein consisting of two dozen amino acids. It may resemble bee venom in structure, and in physical action it may resemble surfactants similar to those found in washing powders,” explained Professor Kasumyan.
As a result, the development of a chemical repellent against sharks was abandoned. Modern spectroscopy allows us to analyze the composition of substances much more accurately than in the 70s, and molecular genetic studies can give a “list” of proteins synthesized by the body, so that science can find out exactly what, hypothetically, saved the soles from predators. But this problem is of little interest to scientists, for which, despite its practical value, large grants are not allocated. Also, any practical test of the repellent would be very expensive anyway.
According to Alexander Kasumyan, sharks are relatively successfully repelled by the smell of their own rotting flesh, and such protective equipment is tried to be used in practice. But if the shark is hungry and smells blood, then such a repellant remains indifferent to it, to the point that it is ready to swallow the bag in which it is located.
Sound and electricity against sharks
Some scientists have suggested removing sharks by physical rather than chemical methods. For example, sharks do not like low-pitched sounds. In addition, they have developed electrosense – living organisms produce electric fields, and some fish sense them, seeking prey. The hypothesis arose that certain electric fields might not attract sharks, but might scare them away, but in practice neither these nor acoustic methods worked.
Potentially, the shark could be more crudely impacted, for example by an explosion. However, TNT bombs thrown into the water will threaten people as well as fish and cause panic among those vacationing at sea. Hypothetically, a device developed by Russian scientists that can have an explosive effect on the aquatic environment without the use of explosives could protect against sharks.
“This technology has a lot in common with shock wave therapy devices used to treat musculoskeletal diseases. A strong electromagnetic pulse transfers energy to water, causing a “shock wave.” This wave can be focused into a narrow beam that can span tens of meters. In simple terms, an analogy to an explosion is the strong impact of an electromagnetic coil on a membrane that is in contact with water from the side.The device is half two meters in size, not counting the onshore power supply.Physicist Alexei Ognevsky, general manager of NPO Shock Wave Technologies, told Gazeta. modern sonar makes it possible to identify aquatic animals and determine their position with an accuracy of several centimeters – such target designation will be quite enough to give a directed impulse, ”Ru said.
From a physical point of view, the beam is not a shock wave (almost not propagated in water), but a non-linear sound with an explosive pressure amplitude profile. The energy of non-linear sound oscillates at the boundary of the medium with different wave impedance – it should feel like a blow or a strong jolt. In the case of a shark, this shaking must occur in the liver because its impedance is different from the rest of the body, but no tests have been done on this particular fish species. There are no problems with sharks in Russia, the developers were discussing the sale of such devices with one of the Middle Eastern countries, but in February 2022, contacts were lost. The estimated cost of a non-linear sound emitter is 10-12 million rubles.
Alexander Kasumyan, in response to a request to comment on such an idea, said that they should be approached with caution. The theory is widespread among ichthyologists that fish do not feel pain in the same sense as mammals and are not afraid of it. However, some serious ailments or damage to the body can scare off the predator.
Source: Gazeta
Barbara Dickson is a seasoned writer for “Social Bites”. She keeps readers informed on the latest news and trends, providing in-depth coverage and analysis on a variety of topics.