OnApril11,2018,ProfessorYangGuangandhisteamfromtheSchoolofLifeSciencesofNanjingNormalUniversitypublishedaresearchreportinNatureCommunications.ThefindingofthisstudyisthattheYangtzefinlessporpoiseanditscloserelative,thema-rineporpoise,haveenoughsignificantandstablegeneticdifferencestolabelthemindependentspecies–whichincreasedthenumberofcetaceanspeciesintheworldfrom89to90.Furthermore,thishasalsoraisedtheimportanceofprotectingtheYangtzefinlessporpoise.
LovelyWaterElves
TheYangtzefinlessporpoiseisasmallcetaceananimal,whichlookssimilartoadolphin.Forthemostpart,itsheadisbluntbuthasaslightfrontalbulgenearitsforehead.Theporpoisehasashort,widerostrum,accompaniedbysmallteethandsmalleyes.Therearenodorsalfinsonitsspine,anditsfinsarelargeandtriangular.Theirbackhasa3-4cmwideridgeinplaceofadorsalfinandmostofitsbodyiscoveredinhornyscales.Itsbodyisgrayorgrayish-whiteanditsabdomenislighterincolorcomparedtotherestofitsbody.Thefinlessporpoisehasabodylengthofabout1.2meters,withthelongestreaching1.9meters,andabodyweightnormallynomorethan200kilograms.
TheseanimalsaremainlydistributedinthemiddleandlowerreachesoftheYangtzeRiver,especiallyinDongtingLake,PoyangLake,andthemainstreamoftheYangtzeRiver.TheyoftenappearinthesectionoftheYangtzeRiverbetweenNanjingandShanghai,wheretheyfeedonfishandshrimps.Withadeepriver,abundantfisheries,andaquaticanimals,thesefinlessporpoiseslovetohuntandhangouthere.
Finlessporpoisesenjoysplashingaroundinthewater.Theirbodyallowsthemtoroll,jump,nod,spraywater,andmakesharpturns.Iftheyarefrightened,theywillswimquicklyandthenjumpabovethesurfaceofthewaterseveraltimesinarow.Withonlytheirtailpropellingthem,theycanlifttheirentirebodyoutofthewater,reachingaheightof0.5meters.
Theseanimalssometimesswimalone,butmoreoftenthannot,theyswiminpairs,especiallywhenmalesandfemaleschaseeachother.Sometimes,femalefinlessporpoisesalsoswimwithitsbaby,providingsafetyintheopenwater.ThefinlessporpoisealsolikestoswimalongsidetheshipsandboatsintheYangtzeRiver.Thewavesmadebythepowerboatsdisturbtheusuallycalmwater,causingtheporpoisestochasethewaves.Peopleontheboatsaresoexcitedtospotthefinlessporpoiseswimming.
Thebreedingseasonbeginsinautumn,roughlyfromSeptembertoOctober.However,itsdeliveryperiodisroughlyinthesamemonthnextyear,whichmeansittakesawholeyeartobreedasmallfinlessporpoise.Accordingtoreports,thelifespanfortheseanimalscanbeaslongas20years.However,finlessporpoisesneedtowaitatleastadayfromthestartofthesignsofbirthuntiltheactualdelivery.Thedeliveryprocesslastsfornearlythreehours.A1992studyshowedthattheannualfertilityrateofthefinlessporpoiseisabout20percent,andtheirsexualdevelopmentstartsattheageoffour.Finlessporpoisesgenerallygivebirthtoasinglecub.
Femalefinlessporpoisesoftentakecareoftheircalvesbyguidingthemwhiletheylearnhowtoswim,aswellascarryingthemonbacktosurfaceeveryafewminutestotakeinfreshair.Sometimesmalefinlessporpoisesalsoparticipateinrearingthecalves,allowingtheyoungtoswimbetweenthefatherandmother.Thefamilywillswimupanddowninthewateratthesametime.Femalefinlessporpoisestendtobeverymotherly.Ifthecubisunfortunatelycaughtbypoachers,themotheralsotendstobecaughtbecauseshewillnotabandonhercub.
ProtectingtheEndangered
Finlessporpoisesaresensitivetothechangesinairflowabovethesurfaceofthewater.Whenheavywindsandrainsareapproaching,theywillbecomemoreactive.Theychaseaftereachotherclosetothewatersurface,causingripplesandsmallwaves.Localfishermenwillthenknowthatstrongwindsortorrentialrainsarecomingiftherearelargenumbersoffinlessporpoises,whichisaveryraresight.Thisindicatesanurgentwarning–ahugestormisonitsway!Accordingtorecords,themostfinlessporpoiseseverseentogetherwas87.
Thesignificantdeclineinthenumberoffinlessporpoisesbeganinthe1980s.Theemphasisontheprotectionoffinlessporpoisebeganin2006.Thisyear,scientistsattemptedtoconductacomprehensivestudyofanothermammal,theChineseBaijidolphin,orLipotesvexillifer,butnoBaijidolphinswerefound.Thefollowingyear,itwasdeclared“functionallyextinct.”
ThefinlessporpoisealsofacesthesamedangerastheBaijidolphin,withitspopulationdrasticallyreducedoverthelastdecadeorso.Thenoiseandpropellersofhigh-density,busyshippingvesselsontheYangtzeRiverhavebecomethebiggestthreattotheirsurvival.Heavyfishingandthemassiveuseofillegalfishinggear,waterpollution,andtheconstructionofwaterconservancyfacilities,alsothreatentheirsurvival.
In2012,scientistsdiscoveredthattherewereonlyabout1,000Yangtzefinlessporpoisesleft,andthepopulationhaddecreasedatanaverageannualrateof13.7percent.ApredictionmadebytheInstituteofHydrobiology,theChineseAcademyofSciencessuggeststhatthespeciescouldvanishfromthewildwithinadecadeifnotimelyandeffectiveprotectivemeasuresaretaken.
Today,thereareeightYangtzefinlessdolphinnaturereservesinChina,andalargenumberofvolunteershavejoinedintheobservationandconservationactivitiesoftheYangtzefinlessporpoise.Since2013,aseasonalfishingbanhasbeenimplementedalongtheYangtzeRiver.
From2017,expertsproposedsuggestionsforacomprehensivefishingbanintheYangtzeRiverbasin.Othereffortsincludeshuttingdownmanylargepollutingenterprises,whiletheremainingenterpriseshaveadoptedmorestringentenvironmentalprotectionmeasures.Inaddition,stricterandmoredetailedenvironmentalimpactassessmentandcontrolsystemhasbeenappliedtonewwaterconservationprojectsandshippingactivities.Withtheimplementationofthosemeasures,thelivingenvironmentoftheYangtzefinlessporpoisehasbeensignificantlyimproved,whileecologicalrestorationworkhasalsostarted.Atthesametime,ChinesescientistshavemasteredtheartificialbreedingtechnologyoftheYangtzefinlessporpoise.Now,someYangtzefinlessporpoiseshavebeenrelocatedtonaturereservesandsofar,everythinggoeswell.Althoughtheecologicalprotectionofwaterareasischallenging,ChinahopesthattheYangtzefinlessporpoisewillonedayreturntoitsoncepopulousnumbers.C
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