All About... Sharks

Sharks are among the oldest animals on Earth; they have ruled the seas for over 400 million years. The two largest kinds of fish are sharks, and both are threatened species. At more than 40 feet long (about the size of a bus!), whale sharks are the biggest fish of all. They are actually harmless to humans. With their huge mouths, they swim along slowly near the surface, filtering tiny plankton out of the water. The basking shark also eats plankton and grows to about 33 feet long. These slow moving fish are easy targets for harpoon fishermen. These sharks can also get tangled in commercial fishing nets.

When most people picture a shark, they think of the streamlined "mackerel" sharks -- like the great white (which are actually pretty rare) -- or "requiem" sharks like the silky shark. But many sharks don't look the way you might imagine. Sharks live in many different parts of the ocean and have developed specialized shapes, teeth, fins, and coloration to fit their habitats. The 350+ species are divided into eight orders. The common names of these types of sharks are: angelsharks, sawsharks, dogfish and cookiecutter sharks, ground sharks, mackerel sharks, carpet sharks, horn sharks, and frilled and cow sharks. About half of all sharks only grow to around 40 inches long. One of the smallest kinds is the seven-inch pygmy spiny shark.

Unlike a tuna or salmon, sharks have no bones. A shark's skeleton is made up of a tough, flexible material called cartilage. Sharks can see, hear, smell, taste, and feel. They also have a sixth sense. Through tiny pores in their heads, they can pick up electrical impulses that every animal emits. This ability, combined with strength and razor-sharp teeth, makes them excellent hunters.

However, sharks have a big enemy of their own: humans. People kill 30 to 70 million sharks each year. The great white may be the top predator of the sea, but its fins, jaws, and teeth are valuable in international markets. Many other types of sharks are also killed for their fins. Shark fin soup is a big favorite in parts of Asia, and it can sell for up to $90 a bowl in Hong Kong. Shark meat is growing in popularity in the U.S. Other parts are used to make health and beauty aids. Some people also hunt sharks for sport. Because sharks reproduce slowly, these killings are a serious problem, and the future of the shark is threatened in many parts of the world.

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