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
30
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://jikaoti.com/ti/nIe7FFFM
0
考研英语一
相关试题推荐
Ithasbeennecessarytoreferrepeatedlytotheeffectsofthetwoworldwarsinpromotingallkindofinnovation.Itshouldbe
Bilingualism,ofcourse,canbealegupforcollegeadmissionandaresumepolisher.Butagrowingbodyofresearchnowoffers
Bilingualism,ofcourse,canbealegupforcollegeadmissionandaresumepolisher.Butagrowingbodyofresearchnowoffers
IndiscussingthesubjectmatterofSF,theauthorfocuseson______.Thistextismostlikelytobe______.
Advancesincomputersanddatanetworksinspirevisionsofafuture"informationeconomy"inwhicheveryonewillhave(1)_____t
In1967,inresponsetowidespreadpublicconcernarousedbymedicalreportsofasbestos(石棉)relateddeaths,theNationalMedica
Youwillgraduatefromuniversityandintendtocontinueyourfurtherstudyoverseas.Writealettertoagraduateschoolto1)
Theclaimsofvegetarianstothemostenvironmentallyresponsibledietsnowappeartobevalidatedbyareportfromleadingscie
影响测试有效性的因素——1995年英译汉及详解Thestandardizededucationalorpsychologicalteststhatarewidelyusedtoaidinselecting,classifyi
Everyday,employeesmakedecisionsaboutwhethertoactlikegiversorliketakers.Whentheyactlikegivers,theycontribute
随机试题
茶叶中儿茶素类的测定一般采用()。
Thereare【C1】_____homesinChinatodaythatdonothaveaTVset.Mostpeople,oldandyoung,liketospendsometimewatchingT
女性患者,50岁,诊断Addison病2年,用激素替代治疗,因外出工作紧张,劳累,终止药物治疗,出现恶心、呕吐、腹痛、腹泻、高热,化验检查:血钠122mmol/L,血糖2.8mmol/L。以下哪项化验检查在该患者中不能出现
确诊膀胱肿瘤最重要的检查方法是
A.β2受体激动剂B.β2受体阻滞剂C.抗胆碱能药D.糖皮质激素E.白三烯调节剂倍氯米松属于
初孕妇,26岁。现妊娠3l周,自述稍做体力劳动觉心悸、气短。能提示患器质性心脏病的检查结果为
小脑疾患,步态呈
设某企业销售三种不同类型的可比商品,其销售量和价格资料如下:根据上述资料请回答:商品销售量综合指数的计算结果为()。
A、9.1%B、10%C、15%D、21%B观察图表,只有财政收入预警发生了变化,从红色变为黄色,因为总共有10个指标(预警指数不算一项),所以2008年6月,发生变化的比例是1÷10×100%=10%。故选B。
【T1】______areactually【T2】______.Whiletheyare,perhaps,【T3】______tomeaningincommunicationinthesamewayasgrammaror
最新回复
(
0
)