- 阅读理解A
题干：Whenprehistoricmanarrivedinnewpartsoftheworld，somethingstrangehappenedtothelargeanimals：theysuddenlybecameextinct.Smallerspeciessurvived.Thelarge,slow-growinganimalswereeasygame，andwerequicklyhuntedtoextinction.Nowsomethingsimilarcouldbehappeningintheoceans.Thattheseasarebeingoverfishedhasbeenknownforyears.WhatresearcherssuchasRansomMyersandBorisWormhaveshownisjusthowfastthingsarechanging.Theyhavelookedathalfacenturyofdatafromfisheriesaroundtheworld.Theirmethodsdonotattempttoestimatetheactualbiomass(theamountoflivingbiologicalmatter)offishspeciesinparticularpartsoftheocean,butratherchangesinthatbiomassovertime.AccordingtotheirlatestpaperpublishedinNature,thebiomassoflargepredators(animalsthatkillandeatotheranimals)inanewfisheryisreducedonaverageby80%within15yearsofthestartofexploitation.Insomelong-fishedareas,ithashalvedagainsincethen.Dr.Wormacknowledgesthatthesefiguresareconservative.Onereasonforthisisthatfishingtechnologyhasimproved.Today'svesselscanfindtheirpreyusingsatellitesandsonar,whichwerenotavailable50yearsago-Thatmeansahigherproportionofwhatisintheseaisbeingcaught，sotherealdifferencebetweenpresentandpastislikelytobeworsethantheonerecordedbychangesincatchsizes.Intheearlydays,too,longlineswouldhavebeenmoresaturatedwithfish.Someindividualswouldthereforenothavebeencaught,sincenobaitedhookswouldhavebeenavailabletotrapthem，leadingtoanunderestimateoffishstocksinthepast.Furthermore，intheearlydaysoflonglinefishing,alotoffishwerelosttosharksaftertheyhadbeenhooked.Thatisnolongeraproblem,becausetherearefewersharksaroundnow.Dr.MyersandDr.Wormarguethattheirworkgivesacorrectbaseline,whichfuturemanagementeffortsmusttakeintoaccount.Theybelievethedatasupportanideacurrentamongmarinebiologists,thatofthe“shiftingbaseline”.Thenotionisthatpeoplehavefailedtodetectthemassivechangeswhichhavehappenedintheoceanbecausetheyhavebeenlookingbackonlyarelativelyshorttimeintothepast.Thatmattersbecausetheorysuggeststhatthemaximumsustainableyieldthatcanbecroppedfromafisherycomeswhenthebiomassofatargetspeciesisabout50%ofitsoriginallevels.Mostfisheriesarewellbelowthat,whichisabadwaytodobusiness.
题目：The author seems to be mainly concerned with most fisheries'_____. - A 、management efficiency
- B 、biomass level
- C 、catch-size limits
- D 、technological application
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参考答案【正确答案：B】
主旨题。第二段第四句提到, 两位研究者关心的不是某个海域鱼群的总量，而是鱼群总量的 历史变化。该段第五、六句, 作者用数字说明了鱼群数量的变化规律。第四段提出，应该根 据不断变化的总量基线来调整捕捞数量，否则就达不到持续发展。可见，如何维持鱼群数量 的可持续水平是作者所主要关注的。B选项正确。
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