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Overfishing Whales and the Environment 过度捕鲸与环境 Until recently, when scientists studied changes in open-ocean ecosystems, they looked at changes in the bottom of the food chain that gradually make their way to the top, like food shortages and shifts in the ocean environment. A recent study, however, suggests that more attention needs to be given to top-down influences as well. 直到最近，当科学家们在研究远洋地区生态系统的变化时，他们观察了处于食物链最底层并且在慢慢上升的变化，比如说食物短缺、海洋环境的变化。然而，最近的一项调查显示，人们还应该更多的注意自上而下的影响。 For example, over the past few decades, theres been a major collapse of the populations ofharbor seals, fur seals, sea lions, and sea otters living on the coasts of western Alaska. Now a new study suggests that all this destruction can be traced back to humans overfishing sperm and baleen whales between 1946 and 1979. 比方说，在过去的几十年里，生活在阿拉斯加西海岸的斑海豹、海狗、海狮和海獭数量极具下降。现在，一项新的调查显示，所有的这些毁坏都可以归咎于人类在1946年到1979年期间过度捕捞抹香鲸和须鲸。 Killer whales, who live at the top of the ocean food chain, used to prey on sperm and baleen whales. When these were no longer available, the killer whales were forced to fish farther down the food chain. First they fed on seals, which were the easiest to catch and the most nutritionallyvaluable. | 
