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In sharks, the ampullae of Lorenzini are electroreceptor organs. They number in the hundreds to thousands. Sharks use the ampullae of Lorenzini to detect the electromagnetic fields that all living things produce. [25] This helps sharks (particularly the hammerhead shark) find prey. The shark has the greatest electrical sensitivity of any animal.
Sharks are much more sensitive to electric fields than electroreceptive freshwater fish, and indeed than any other animal, with a threshold of sensitivity as low as 5 nV/cm. The collagen jelly, a hydrogel , that fills the ampullae canals has one of the highest proton conductivity capabilities of any biological material.
In 1995 researchers found that sharks have a heightened sensitivity to low frequency electrical fields, at a close range. This helped with the development of technologies like SharkShield, which is a product that is used for various water-sport activities (such as surfing) that emits a 3-D electronic field that surrounds person who is using it.
Active electroreception typically has a range of about one body length, though objects with an electrical impedance similar to that of the surrounding water are nearly undetectable. [12] [13] [14] Active electrolocation relies upon tuberous electroreceptors which are sensitive to high frequency (20-20,000 Hz) stimuli.
In the first 11 months of 2013, 633 sharks were captured in Queensland — more than 95% of those sharks died. [42] From 2013 to 2014, 667 sharks died in Queensland's "shark control" program, including great white sharks and critically endangered grey nurse sharks. [35] From 2014 to 2015, 621 sharks died in Queensland. [43]
Shark repellents are a category of animal repellents. Shark repellent technologies include magnetic shark repellent, electropositive shark repellents, electrical repellents, and semiochemicals. Shark repellents can be used to protect people from sharks by driving the sharks away from areas where they are likely to harm human beings.
The shark has the greatest electrical sensitivity of any animal. Sharks find prey hidden in sand by detecting the electric fields they produce. Ocean currents moving in the magnetic field of the Earth also generate electric fields that sharks can use for orientation and possibly navigation. [65]
Ocean Guardian is the manufacturer of Shark Shield shark repellent devices. The Ocean Guardian electronic devices create an electromagnetic field to deter shark attacks and are used by surfers, scuba divers, snorkelers, spearfishers, ocean kayak fishers, swimming areas off boats and for ocean fishing.