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  3. Trawling (用拖网捕鱼) the seabed for fish is an environmental disaster; it wrecks ecosystems, destroys fish stocks and leaves behind

Trawling (用拖网捕鱼) the seabed for fish is an environmental disaster; it wrecks ecosystems, destroys fish stocks and leaves behind

admin2017-11-08  51
问题    Trawling (用拖网捕鱼) the seabed for fish is an environmental disaster; it wrecks ecosystems, destroys fish stocks and leaves behind a marine desert. Right? Environment campaigners say so. But there is growing evidence that the effect is sometimes very different, with trawling increasing fish stocks from the North Sea to the California coast. A new modeling study may for the first time have demonstrated why.
   Trawlers attach large nets to a metal beam dragged across the seabed to catch bottom-dwelling fish. Greenpeace compares it to "driving a huge bulldozer through a forest", leaving a flat, featureless desert on the seabed. Trawling clearly does remove fish, such as large crustaceans and shellfish, says Daniel van Denderen of the Wageningen Institute for Marine Resources and Ecosystem Studies in the Netherlands. But this is a lucky break for softer, smaller species lurking in the sandy seabed, such as worms. They survive and, with fewer rivals, flourish.
And if, as is often the case, these smaller critters are the main food for fish, then the overall effect is to nurture more marine life. Imants Priede, director of Oceanlab at the University of Aberdeen, UK, says there is growing evidence that—while far from universal—the phenomenon is real. "On continental shelves such as the southern North Sea, where shifting sands and gravels are stirred up by strong tidal currents, even trawling more than once a year may be beneficial for some fish stocks," he says.
   In fact, studies going back 20 years have linked persistent trawling with increased fish stocks. The cause of this counter-intuitive finding has remained uncertain. Some have suggested that trawling stirs up the seabed, throwing potential food into the water column—rather like ploughing a field. Others think that discards from fish nets add to the food available on the sea floor. But van Denderen is the first to show how trawling can stimulate fisheries simply by drifting from ecosystems. "The findings are very important," says Priede.
What is not the possible reason for the increasing fish stocks by trawling?
选项 A、Trawling stirs up the seabed and leaves potential food into the water.
B、Discards from trawling make more food available on the sea floor.
C、Trawling can stimulate fisheries because of drifting from ecosystems.
D、Trawling makes seabed be more flat and featureless, which is beneficial for fish survive.
答案D
解析 根据四个选项可以将该题定位至文章最后一段。第四段第二句The cause of this counter-intuitive finding has remained uncertain指出“原因仍不明确”。然后讲述了人们对原因的一些猜测和研究。根据该段提到的三个原因可以将A、B、C三个选项排除，选出D选项。
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