When we talk about sharks, we always feel afraid of them. But you are wrong when you say they are harmful.(有害的） Instead, they are amazing animals that need our respect(尊重) and protection. They have played an important role in the ocean’s food chain(食物链) in the last 400 million years.

 
    Those who regard sharks as terrible animals may not know that only 6% of the 250 kinds of sharks are harmful to humans. （在250种鲨鱼里，只有6%的种类对人类有害）They fail to realize that sharks’attacks don’t happen very often. Even the Great White Sharks won’t attack humans in their path（路线） unless they are really very hungry. So humans are more likely to be killed by lightning(闪电) than by a shark.

    Not long ago, a shark exhibition at the National Aquarium in Baltimore, （巴尔第摩国家水族馆）US, proves(证明) this. Visitors can touch young sharks, see their eggs develop and watch more than 10 different kinds of sharks swim smoothly around a huge tank.

 
    It’s a pity that the population of sharks has been  badly cut down. In the year 2003, a study in the US found that almost all recorded shark kinds have fallen by half in the past 8 to 15 years. On one hand, many sharks are killed by humans for their fins(鱼翅), because the fins can be made into sharks’fin soup. On the other hand, sharks cannot breed(繁殖) fast like other fishes — some are pregnant(怀孕的) for 2 or 3 years before giving birth. It means that their number can easily be reduced (减少) by too much fishing. This is why scientists believe that shark fishing should be regulated (控制).