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游戏，猎物(根据语境，选这个意思), 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(渔场,是fishery的复数形式)  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(变成一半，是half的改f为ved，变成“减半”的意思) again since then.

        Dr. Worm acknowledges that these figures are conservative. One reason for this is that fishing technology has improved. Today’s vessels船只 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 would have been more saturated浸透，饱满 with fish. Some individuals would therefore not have been caught, since no baited带鱼饵的 hooks 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.

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1.记忆vessel这个单词,vessel(人或动物的）血管，（植物的）导管；船，舰；容器，器皿),记忆法谐音“尾蛇”，尾蛇长长的一条，就像(人或动物的）血管的血管一样，就像植物的导管一样，它在水里游起来就跟船只一样，它盘起来的时候就像盛放东西的容器一样。

2.saturate浸透，饱满。在原文是指，使鱼能在捕鱼网上更加饱满，言外之意就是在渔网上捕捞到