'Sharkcano': How magnets can repel sharks and other cool facts you did not know about the magnificent creatures
Sharks are terrifying creatures, but they also happen to be magnificent ones that hold many secrets of life itself. For instance, did you know that sharks can detect changes in a magnetic field? It is this same sensitivity that perhaps helps some sharks even find their way to underwater volcanoes, where molten lava is highly magnetic. This is the subject of National Geographic's latest special in its Sharkfest line of programming, 'Sharkcano'.
A few years earlier, scientists were shocked to discover that two species of shark dwelled in the burning waters near an underwater volcano. A group of scientists surveying Kavachi, a very active volcano 60 feet below the ocean’s surface near the Solomon Islands, found that hammerhead sharks and silky sharks lived in the burning, acidic waters near the volcano.
In 'Sharkcano', Dr Michael Heithaus and his team placed strong artificial magnets on the seabed to see if sharks were attracted to the magnetic field. What they discovered was that hammerhead sharks and nurse sharks were not only attracted to them, but the latter also tried to eat them. The ocean floor soon got agitated by all the sharks that had swum to the area.
That sharks have the ability to detect magnetic fields and changes in magnetic fields are not new. But, there are quite a few facts about the ocean predator's ability that might leave you surprised. What helps sharks detect electric and magnetic fields in water are special sensing organs called ampullae of Lorenzini which consists of a network of jelly-filled pores. When animals contract their muscles they produce an electric field. Sharks can detect the weak electric fields generated by muscle contractions and may use it to find prey.
Sharks also use their detection of the earth's magnetic field in their hunt for prey. They can follow Earth’s magnetic field and use it to navigate. Studies have proven that sharks can detect magnetic fields in water and use them to locate prey in the ocean.
There is one species of shark that uses this ability to get the prey to come to them. Lemon sharks, named for their yellowish coloring, have a magnetic sensor in their noses. With this special magnetic sensor, they can attract prey and even find other lemon sharks to mate with. The magnetic sensors in their noses help them make up for their poor vision.
But here's where the shark's ability to detect magnetic fields can be used to help them. Each year, roughly 100M sharks of all species are killed for many reasons, especially as they are hunted for their fin, a delicacy enjoyed in East Asia and Brazil. Researchers at the University of Newcastle in Australia developed new tech that uses sharks' electrical sensitivity to deter them from fishing traps. The team outfitted a third of the traps deployed near Sydney, Australia, with magnets around their entrances, another third with metal bars, and the rest were unchanged and left alone. The scientists found that the magnets reduced the total catch of the sharks by about 30 percent.
'Sharkcano' airs on National Geographic on July 21 at 10/9c.