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  3. Across the western United States alone, trout(a kind of fish)fishing generates hundreds of millions of dollars annually. But tro

Across the western United States alone, trout(a kind of fish)fishing generates hundreds of millions of dollars annually. But tro

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问题     Across the western United States alone, trout(a kind of fish)fishing generates hundreds of millions of dollars annually. But trout habitat will likely be cut in half by 2080 due to warming rivers and altered patterns of flooding, according to a large study published online in the Proceedings of the National Academy of Sciences, " It’s fairly shocking to us, as biologists," says co-author Kurt Fausch of Colorado State University, Fort Collins. This is not a case of winners and losers; the four species examined by the team are all likely to decline to varying degrees.
    By running several climate models and plugging in data on habitat characteristics and fish present at 9,890 locations in the Rocky Mountains and Great Basin, the team of scientists created predictions for trout habitat across more than 1 million square kilometers of the western United States. They factored physical aspects of habitat—water temperature, patterns of flooding—as well as competition among species. Here’s what the study concludes about the future of trout:
    Introduced beginning in the 1800s for fishing, rainbow trout live in larger rivers than do the other species. They typically grow up to 110 centimeters long and are relatively easy to catch. Increases in water temperature will restrict their range, but rainbow trout dodge a bullet. Climate change will mean more frequent and intense winter floods, which can scour away eggs laid in the fall, but rainbow trout spawn in the spring. The size of their habitat is predicted to decline by 35%.
    Smaller than rainbow trout, Brown trout are the most temperature tolerant among the four species and like warmer temperatures. They have the ill fortune to spawn in the fall, so the increased flooding will make many streams inhospitable. Their habitat is predicted to decline by 48%.
    As to Cutthroat trout, the range of these native fish has already shrunk by more than 85% due to competition from introduced species. Two subspecies have already gone extinct. Warming temperatures and continued competition primarily from rainbow trout are predicted to reduce suitable habitat by a further 58%.
    Compared with the other species, brook trout are the biggest losers in 2080. Because they spawn in the fall, the increase in winter flooding is expected to reduce their suitable habitat by 77%—a surprising amount given their success at invading new habitat. "I did not expect brook trout to decline so much," says co-author Seth Wenger, a biologist with Trout Unlimited, a conservation organization in Boise.
    Frank Rahel, a fish ecologist at the University of Wyoming in Laramie, who was not involved with the study, says the findings help paint the big picture for trout this century. "They’re very sobering results that will catch people’s attention," he says. Not much can be done to reduce the impact of winter floods, but managers already try to keep streams cooler by planting trees and shrubs.
Although brook trout adapts to new environments well, it
选项 A、cannot compete with rainbow trout in the skill of invasion.
B、has to face the worst situation in the future since it lays eggs in the fall.
C、cannot adjust well to warmer temperatures as well as winter flooding.
D、has to face the most serious problem arising from its overpopulation.
答案B
解析 事实细节题。根据题干中的brook trout定位到第六段第二句可知，冬季洪水会使河鳟的栖息地急剧减少，因为这种鱼是在秋季产卵。这使得河鳟与其他鳟鱼相比，在生存方面面临最严重的危险。因此[B]与原文意思相符，故为答案。虽然虹鳟和河鳟都会入侵新的栖息地，但文章并未对此作比较，因此[A]“在入侵技术方面比不过虹鳟”不符合文意；[C]“无法很好地适应水温变暖及冬季洪水中水温变暖问题”该段未提及，故排除。
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