Type of sharksThere are at least 350 species of shark ranging from the smallest, the pygmy ribbontail catshark (8 to 10 inches long) to the largest, the whale shark (upto 45 feet long). Sharks are equipped with a special set of sensors, arranged in clusters over their heads, that can pick up electromagnetic currents emitted from other animals. Sharks have bad eyesight, but these sensors help detect prey from 1 to 3 yards away. Sharks can also detect the electromagnetic fields of the Earth and may use this ability to guide them during migration. Sharks are often thought of as cold-blooded killers that prey on humans. However, only 32 species have been known to attack humans, and most attacks are accidents. Often, sharks inhabit the same shallow, warm-water areas as humans. The shark may mistake a person standing or floating in water for natural prey. The shark goes in for the kill but, after one taste, usually gives up the attack. Many shark attacks involve people trying to free sharks from fishing nets. Sharks also are territorial animals and may attack if they feel threatened. The chances of being attacked by a shark are very small, and the chances of dying from a shark attack have greatly decreased over the years. In fact, in the United States, a person is 30 times more likely to be killed by lightning than by a shark. Dog bites are 1,000 times more common than shark bites. Sharks are fished for their fins and cartilage. Shark-fin soup is a popular food in some areas. After the fin is cut off, the rest of the shark is discarded. Shark cartilage is a subject of much scientific study because medicine made from it may stop the growth of tumors. Shark cartilage is sold in ...
