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
48
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.
What contributes most to the overfishing of sharks is ______,
选项
A、the sharks accidentally captured by tuna fishers
B、the rough few decades that sharks have suffered
C、the ever-increasing demand for their fins and meat
D、the millions of sharks killed deliberately each year
答案
C
解析
根据第二段第二句“Demand for their fins and meat has resulted in increasing exploitation,…”,C应为答案。
转载请注明原文地址:https://kaotiyun.com/show/JWzZ777K
0
考研英语一
相关试题推荐
TheEconomistrecognizesthesetalentedpeoplethroughitsannualInnovationAwards,presentedinsixfields:bioscience,comput
Inmostpeople’smind,growthisassociatedwithprosperity.WejudgehowwelltheeconomyisdoingbythesizeoftheGrossNat
Inmostpeople’smind,growthisassociatedwithprosperity.WejudgehowwelltheeconomyisdoingbythesizeoftheGrossNat
Economics,asweknowit,isthesocialscienceconcernedwiththeproduction,distribution,exchange,andconsumptionofgoods
Whatmaybetheattitudeofmanypublic-serviceworkerstowardsthestrategyofBlair’sgovernment?TheviewsofGordonBrowna
Advancesincomputersanddatanetworksinspirevisionsofafuture"informationeconomy"inwhicheveryonewillhave(1)_____t
ReduceWaste-FoodExpertsinthefoodindustryarethinkingalotabouttrashthesedays.Restaurants,colleges,hospitalsa
Whenadiseaseofepidemicproportionsthreatensthepublic,scientistsimmediatelygettowork,tryingtolocatethesourceof
Agreatmanycreatureshavewhatarecalledwarningcolours,thatistosay,thecolourationwarnseverycreaturethattheanima
Clearly,aperson’sdecisionsaredeterminedbycircumstances.Experimentsconductedoverthepastfewyearshaverevealedthat
随机试题
Lily:Hi,Jim!Howwasyourparty?Jim:It’swonderful!【D8】________Lily:I’msorry.Ihadplannedto,butIhadahighfeverth
我哭小弟,哭他在剧痛中还拿着那本航空资料“想再看看”,哭他的“胃下垂”、“肾游走”;我也哭蒋筑英抱病奔波,客殇成都;我也哭罗健夫不肯一个人坐一辆汽车!我还要哭那些没有见诸报章的过早离去的我的同辈人。他们几经雪欺霜冻,好不容易奋斗着张开几片花瓣,尚未盛开
超文本是指()
下述何种病的肺功能主要表现为限制性通气功能障碍
2020年7月北京某公司(为一般纳税人)在深圳转让某县城的一处房产,2016年2月购进价52万元,转让价65万元,该公司销售不动产选择按简易计税方法计税,以上价格均为不含税价,下列说法正确的有()。
如图所示,AD是∠FAB的角平分线,延长AF与⊙O的切线CD交于C,AB是⊙O的直径.若DE⊥AB,证明:AE.BE=AC.CF.
设幂级数的收敛半径分别为存在,则幂级数的收敛半径为().
下列关于列表框和组合框的叙述中,正确的是
Talkingaboutyourcompany谈论公司
Morethan50yearsago,thepsychologistCarlRogerssuggestedthatsimplylovingourchildrenwasn’tenough.Wehavetoloveth
最新回复
(
0
)