首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
考研
Overfishing of one of the ocean’s top predators has triggered a lethal chain reaction that threatens to decimate populations of
Overfishing of one of the ocean’s top predators has triggered a lethal chain reaction that threatens to decimate populations of
admin
2015-09-30
32
问题
Overfishing of one of the ocean’s top predators has triggered a lethal chain reaction that threatens to decimate populations of bay scallops, oysters, and clams, warns a new study. Plunging populations of 11 large shark species have caused a spike in the numbers of their prey, including smaller sharks, rays, and skates. These creatures in turn are wiping out other marine organisms and may be destroying sea grass habitat, which serves as a nursery for many species.
Sharks have had a rough few decades. Demand for their fins and meat has resulted in increasing exploitation, and the creatures are often accidentally captured by swordfish and tuna fishers. As many as 73 million sharks are killed annually, and past studies have indicated many populations have been cut by half. Nonetheless, scientists have had difficulty gauging the decline in several shark species over the years because of a lack of data. The effect of this decline on ocean ecosystems has also proven hard to measure.
To get a better grip on the problem, marine biologist Julia Baum of Dalhousie University in Halifax, Canada, and colleagues trawled 35 years of marine surveys and fisheries data to document declines in large sharks off the eastern seaboard of the U. S. The numbers, reported today in Science, are stark: The blacktip shark population has plummeted 93% since 1972, with similar declines for tiger, bull, and smooth hammerhead sharks.
Simultaneously, the abundance of 12 of the 14 species that these sharks prey on—including the little skate, the chain catshark, and the cownose ray—increased dramatically. The latter has seen its numbers swell ten fold. The jump in ray numbers is especially troubling, notes co author and marine biologist Charles Peterson of the University of North Carolina at Chapel Hill, because the fish shred the sea grass that houses crabs and clams. In fact, he notes, by 2004 ray predation had shut down North Carolina’s century-old bay scallop fishery.
The 11 other shark prey species whose populations rose over the 35-year period could be having similar impacts to that of the cownose ray, says Baum.
"The result is profound" because the high diversity of fishes in the northwest Atlantic has been thought to minimize catastrophic changes in the food web, says marine scientist Kenneth Frank of the Bedford Institute of Oceanography in Dartmouth, Canada. Sharks are only part of the puzzle, however, Frank warns. People’s appetites for oysters, clams, and scallops are likely having a more direct impact on these populations, he says.
The overfishing of sharks may result in______.
选项
A、the abundance of sea grass habitat
B、the ruin of nursery for many marine species
C、the obvious increase of most marine species
D、the huge decline of the populations of their prey
答案
B
解析
根据第一段最后一句中的“These creatures…may be destroying sea grass habitat,whichserves as a nursery for many species”,B应为答案。
转载请注明原文地址:https://jikaoti.com/ti/iIe7FFFM
0
考研英语一
相关试题推荐
Inthefollowingtext,somesentenceshavebeenremoved.ForQuestions41-45,choosethemostsuitableonefromthelist(A、B、C、
Inmostpeople’smind,growthisassociatedwithprosperity.WejudgehowwelltheeconomyisdoingbythesizeoftheGrossNat
Bilingualism,ofcourse,canbealegupforcollegeadmissionandaresumepolisher.Butagrowingbodyofresearchnowoffers
Whatmaybetheattitudeofmanypublic-serviceworkerstowardsthestrategyofBlair’sgovernment?TheviewsofGordonBrowna
Advancesincomputersanddatanetworksinspirevisionsofafuture"informationeconomy"inwhicheveryonewillhave(1)_____t
Inalmostallcases,thesoftpartsoffossilsaregoneforeverbuttheywerefittedaroundorwithinthehardparts.Manyoft
ThedealagreedonThursdaylookspromisinginthat______.Inwhatcasemighttheescapeclausesapplyinreform-aversenation
Assummerrollsaround,lawmakersinWashingtonarepreparingtovoteonajobsbillthatwouldinclude$1billionforsummerjo
AboutHollywoodMorethan41millionAmericanstunedinonMarch7thtowatch"TheHurtLocker"wintheawardforbestpictu
Agreatmanycreatureshavewhatarecalledwarningcolours,thatistosay,thecolourationwarnseverycreaturethattheanima
随机试题
伸直型肱骨髁上骨折多见于
保税货物的稽查期限为海关监管期内。()
关于基金管理公司监察稽核制度的表述,错误的是()。
费里德曼的货币需求函数强调的是()。
数字摄像机的主要优点有()。
为促进混合所有制经济发展,A省于2018年6月召开专家研讨会,向与会专家征求意见和建议。在现行经济社会条件下,下列建议具有可行性和针对性的是()。①探索国有企业公司制改革的有效途径,坚持因企施策②完善股份制形式,促进公有资本与非公有资本交叉持股
请认真阅读下列材料,并按要求作答。低年级美术课堂教学中,如何培养学生的想象力?
当国家公务员认为自己受到单位的不公平待遇时,可以向哪个部门提出申诉?()
认为教育并不能提高人的能力,只是区别不同人的能力的理论是()
Thewordhorsepowerwasfirstusedtwohundredyearsago.JamesWatthadmadetheworld’sfirstwidelyused(11).Hehadnow
最新回复
(
0
)