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
47
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 populations of bay scallops, oysters, and clams are threatened directly by______.
选项
A、the high diversity of fishes in the northwest Atlantic
B、the catastrophic changes in the food web in the Atlantic
C、the lethal reaction triggered by the overfishing of sharks
D、the strong desire of many people for them as their delicious food
答案
D
解析
根据本文最后一句“People’s appetites for oysters,clams,and scallops are likely having amore direct impact on these populations,he says”,D应为答案。
转载请注明原文地址:https://kaotiyun.com/show/XWzZ777K
0
考研英语一
相关试题推荐
AmandatorytraceabilitysystemintheUnitedStateswouldhelpimprovethesafetyoffood,suchasproduce,ahealthofficialt
Ithasbeennecessarytoreferrepeatedlytotheeffectsofthetwoworldwarsinpromotingallkindofinnovation.Itshouldbe
Onethingthatdistinguishestheonlineworldfromtherealoneisthatitisveryeasytofindthings.TofindacopyofTheEc
IncontrasttoBritain,FranceisfundingtheirmedicalcareConcerninghealth-caresystemsinBritain,theauthorislikelyto
TheInlandRevenueonThursdayaccusedtheBritishfilmindustryofabusinggovernmentaid,witheveryproductionofrecentyear
Gingrichianpoliticiansreluctanttoaddresstheproblembecause______.Thecomputermodelsfailedtopicturerealitybecause__
OurculturehascausedmostAmericanstoassumenotonlythatourlanguageisuniversalbutthatthegesturesweuseareunderst
ThedomesticeconomyintheUnitedStatesexpandedinaremarkablyvigorousandsteadyfashion.Therevivalinconsumerconfiden
JohnBattelleisSiliconValley’sBobWoodward.OneofthefoundersofWiredmagazine,hehashungaroundGoogleforsolongtha
Theclaimsofvegetarianstothemostenvironmentallyresponsibledietsnowappeartobevalidatedbyareportfromleadingscie
随机试题
Derivationalaffixescanbefurtherdividedinto______andsuffixes.
A.EPOB.G-CSFC.TNFD.TPOE.IFN可以用于肾癌和恶性黑色素瘤治疗的细胞因子是
场外资金清算流程包括( )。
下列选项中,()属于个案辅导关系的充分必要条件。
甲向乙买了一幅名画,后来发现此画并非真迹,而是复制品。甲退回该画,并要求乙退还其支付的价款,乙拒绝,甲于是诉至法院。经查,乙在购买此画时也不知是复制品,故卖给甲时也以为是真迹,无隐瞒之情。问:此案应如何处理?
下列关于高等学历教育的说法错误的是()。
“庚款兴学”中设立的“游美学生监督处”设在()
已知B=,矩阵A相似于B,A*为A的伴随矩阵,则︱A*+3E︱=_________________________。
Tounderstandinterculturalcommunication,weseektounderstandtraditionandmodernization.
HostilitytoGypsieshasexistedalmostfromthetimetheyfirstappearedinEuropeinthe14thcentury.TheoriginsoftheGyps
最新回复
(
0
)