The shark is a predatory cartilaginous fish, which became, through the efforts of filmmakers, the embodiment of the horror of the seas and oceans. In fact, according to statistics, in 2009, 2251 people were attacked by sharks worldwide, 464 of whom died. For comparison, in the same year in the United States alone, 43,000 people died in road accidents.
Nevertheless, almost half a thousand people are not enough at all. Scientists have long been looking for ways to scare away sharks. In 1937, the beaches of Sydney began to be fenced off with fixed nets at night. After that, not a single shark attack on a person was recorded in the fenced areas. Moreover, the number of these predators caught in the nets at night decreased from year to year - either sharks in the seas became less and less, or they learned to recognize danger.
In 1952, nets as protection against sharks began to be used in Durban (South Africa) with the same success - not a single attack on bathers. However, this method has a significant drawback - harmless animals die in the nets, over which there is already a threat of extinction: dolphins, sea turtles, etc.
The shark has very sensitive sensors that detect weak currents and sound vibrations, as well as odors. This feature of predators is used to create various repellents (repellents). A weak electromagnetic field, safe for other marine life and humans, can stop the shark and force it to stay away from the emitter.
American scientists have developed the Shark Shield device. It can be attached to a boat, surfboard or compressed air cylinder. The generated electromagnetic radiation, according to the developers, is capable of keeping a shark at a distance of several meters.
The sound emitter is similarly arranged. The shark perceives low sound and infrasound. High frequencies make her uncomfortable. It is assumed that the ultrasound generator will scare off the predator. However, tests of all types of emitters have shown that there is no universal repellent: one that repels shark of one species is ignored by another.
Chemical means of protection against these formidable fish are also being developed. It has been noticed that sharks try to stay away from the decaying corpses of their relatives. Scientists have synthesized a substance that mimics the cadaverous shark odor. Experimental tests have shown a certain effectiveness of this tool.
