Question

    When prehistoric man arrived in new parts of the world, something strange happened to the large animals. They suddenly became extinct. Smaller species survived. The large, slow-growing animals were easy game, and were quickly hunted to extinction. Now something similar could be happening in the oceans.

That the seas are being overfished has been known for years. What researchers such as Ransom Myers and Boris Worm have shown is just how fast things are changing. They have looked at half a century of data from fisheries around the world. Their methods do not attempt to estimate the actual biomass (the amount of living biological matter) of fish species in particular parts of the ocean, but rather changes in that biomass over time. According to their latest paper published in Nature, the biomass of large predators (animals that kill and eat other animals) in a new fishery is reduced on average by 80% within 15 years of the start of exploitation. In some long-fished areas, it has halved again since then.

Dr. Worm acknowledges that the figures are conservative. One reason for this is that fishing technology has improved. Today's vessels (船)can find their prey using satellites and sonar, which were not available 50 years ago. That means a higher proportion of what is in the sea is being caught, so the real difference between present and past is likely to be worse than the one recorded by changes in catch sizes. In the early days, too, longlines (多钩长线) would have been more filled with fish. Some individuals would therefore not have been caught, since no baited hooks (带饵钩)would have been available to trap them, leading to an underestimate of fish stocks in the past. Furthermore, in the early days of longline fishing, a lot of fish were lost to sharks after they had been hooked. That is no longer a problem, because there are fewer sharks around now。

Dr. Myers and Dr. Worm argue that their work gives a correct baseline, which future management efforts must take into account. They believe the data support an idea current among marine biologists, that of the “shifting baseline". The idea is that people have failed to detect the massive changes which have happened in the ocean because they have been looking back only a relatively short time into the past. That matters because theory suggests that the maximum sustainable yield （产量）that can be cropped from a fishery comes when the biomass of a target species is about 50% of its original levels. Most fisheries are well below that, which is a bad way to do business.

1.The extinction of large prehistoric animals is noted to suggest that .

A.large animals were easily hurt in the changing environment

B.small species survived as large animals disappeared

C.large sea animals may face the same threat today

D.slow-growing fish outlive fast-growing ones

2.By saying these figures are conservative , Dr. Worm means that .

A.fishing technology has improved rapidly

B.the catch-sizes are actually smaller than recorded

C.the marine biomass has suffered a greater loss

D.the data collected so far are out of date

3.Dr. Myers and other researchers hold that .

A.people should look for a baseline that can't work for a longer time

B.fisheries should keep the yield below 50% of the biomass

C.the ocean biomass should restore its original level

D.people should adjust the fishing baseline to changing situation

Answer

1.C

2.C

3.D

【解析】

这是一篇说明文。文章主要讲了大型史前动物的灭绝表明，大型海洋动物今天可能面临同样的威胁。迈尔斯博士和其他研究人员认为人们应该根据变化的情况调整捕鱼基线。

1.推理判断题。根据第一段Now something similar could be happening in the oceans.（现在，类似的事情可能正在海洋中发生。）由此推断出，大型史前动物的灭绝表明，大型海洋动物今天可能面临同样的威胁。故选C。

2.句意猜测题。根据第三段One reason for this is that fishing technology has improved. Today's vessels (船)can find their prey using satellites and sonar, which were not available 50 years ago. That means a higher proportion of what is in the sea is being caught, so the real difference between present and past is likely to be worse than the one recorded by changes in catch sizes.（原因之一是捕鱼技术的进步。今天的船只可以使用卫星和声纳来寻找猎物，这在50年前是不可能的。这意味着更多的海洋生物被捕捞，所以现在和过去之间的真正差异可能比捕捞量的变化所记录的更糟糕。）由此推断出，通过说“these figures are conservative”，沃姆博士的意思是海洋生物量遭受了更大的损失。故选C。

3.推理判断题。根据最后一段Dr. Myers and Dr. Worm argue that their work gives a correct baseline, which future management efforts must take into account.（迈尔斯博士和沃姆博士认为，他们的工作给出了一个正确的基线，未来的管理工作必须考虑到这一点。）由此推断出，迈尔斯博士和其他研究人员认为人们应该根据变化的情况调整捕鱼基线。故选D。