gray whale foraging occurrence in the northeastern chukchi sea…€¦ · foraging gray whales...
TRANSCRIPT
Overview Foraginggraywhales(Eschrich'usrobustus)weredocumentedinthenortheasternChukchiSeainsummerandfall2015bytheAerialSurveysofArcAcMarineMammals(ASAMM)project.ASAMMlinetransectsurveys,conductedbytheMarineMammalLaboratoryandfundedandco-managedbytheBureauofOceanEnergyManagement,wereconductedintheeasternChukchiSea,67°-72°Nand155°-169°W,fromJulythroughOctober2009-2015.ThenortheasternChukchiSeaisanimportantforagingandweaninggroundforgraywhales.TheytypicallybegintoarriveinthenortheasternChukchiSeainJuneandJuly,feedheavilyinJulyandAugust,andmigratesouthinSeptemberandOctober.Feedinggraywhalesaccountedfor58%ofthetotalgraywhalessightedoneffortin2015,similarto2009-2014(50-76%oftotalgraywhalessightedoneffortperyear).FeedinggraywhalesighAngrate(SR,numberofwhalesoneffortperkmflown)insummer2015washigherthansummerSRsin2009-2014,butfall2015SRwaslowerthanthemeanfallSRfrom2009-2014.GraywhalesweresightedforagingpredominantlybetweenPointBarrowandIcyCape,similarto2009-2014.However,comparedtopreviousyears,graywhalesin2015weresightedfartheroffshoreinJuly,werenotsightedasfaroffshorebetweenPointFranklinandIcyCape,andwerenotsightedeastof157.8°W.
Discussion • ThedifferencesindistribuAonandrelaAveabundancefrom2015and
previousyearscouldbeduetochangesinpreydistribuAonresulAngfromchanginghydrographiccondiAonsandoceanicproducAvityorfromintensefeedingbygraywhales.
• GraywhalesdocumentedintheChukchiSeaoverlayareasofdensebenthicamphipodcommuniAes(BlanchardandFeder2014,Schonbergetal.2014),anditisassumedthatgraywhalesassociatedwithmudplumesinthisareaarefeedingonthisprey.
• AsglobalclimatechangeacceleratesandmulA-yearseaiceconAnuestomelt,benthic-dominatedecosystemsoftheBeringandChukchiseasmaybecomepelagic-dominated(Grebmeieretal.2006).
• GraywhaleshaveaflexibleandopportunisAcforagingstrategyandmayshi_theirforaginghabitsfromthebenthic-tothepelagic-dominatedecosystem.
• ThespaAal,temporal,andinterannualchangesingraywhaleforagingdistribuAonandrelaAveabundancehighlighttheneedforconAnuedbroad-scaleaerialsurveyseachsummerandfall.
Acknowledgements: Thisstudyisfundedandco-managedbytheBureauofOceanEnergyManagementandNOAA(IANo.M11PG00033)andwassupportedCarolFairfield(BOEMCOR).AtMML,addi'onalsupportwasprovidedbyRobynAngliss,StefanBall,PhilClapham,NancyFriday,KimShelden,JaniceWaite,andadministra'vepersonnel.AtJISAO,supportwasprovidedbyAmyKennedyandadministra'vepersonnel.Inaddi'ontotheauthors,numerousdedicatedbiologistshavepar'cipatedinthesesurveys.ClearwaterAir,Inc.pilotssafelynavigatedusthroughtheskies.Real-'meflightfollowingviasatellitelinkwasprovidedbyDepartmentofInteriorpersonnel.ProgrammingsupportwasprovidedbyMikeHay(XeraGIS).Withoutallofthesepeople,oursurveyswouldnothavebeenpossible;oursincerestthankstoall!
TheviewsexpressedorimpliedherearethoseoftheauthorsanddonotreflecttheposiAonsoftheNaAonalMarineFisheriesService,NaAonalOceanicandAtmosphericAdministraAon,orDepartmentofCommerce.
Figure 1. ASAMMon-effortsurveyflightlines,2015.
Methods & Survey Effort
Amelia Brower, Amy Willoughby–JointInsAtutefortheStudyoftheAtmosphereandOcean,UniversityofWashington,[email protected] Clarke–LeidosMegan Ferguson –MarineMammalLaboratory,AlaskaFisheriesScienceCenter,NMFS,NOAA
Gray Whale Foraging Occurrence in the Northeastern Chukchi Sea, Summer and Fall 2015
• Linetransectaerialsurveys
• Twinengineturbopropaircra_
• 2July–30October2015
• 1200_(366m)intheChukchiSea
• 1500_(457m)intheBeaufortSea
• Surveyeffort:“on-effort”(transectandcirclingfromtransect),“off-effort”(searchandcirclingfromsearch),ordeadhead
• ~34,300kmflownoneffortinsurveyblocks12-22in2015(Figure1).
• SighAngRate(SR):Numberofon-effortfeedingwhalesperon-effortkilometersurveyed(whalesperuniteffort,WPUE).
• 2015hadthehighestsummerSR(WPUE=0.0120)(Figure2),despitepoorweatherthatreducedsurveyeffortinJuly.
• Fall2015SR(WPUE=0.0013)waslowerthantheFallSRinsomepreviousyears(Figure2)andlowerthanthemeanSRfrom2009-2014(meanWPUE=0.0016),possiblyduetodifferingsurveyprotocolsduringtheArcAcAerialCalibraAon
In2015,foraginggraywhalessightedoneffortinallmonthsweredocumentedpredominantlyinwater<55mdeepintheseareas(Figure3):
• PointBarrowtoPointFranklin10-30kmfromshore
• NNWofWainwright25-40kmand65-90kmfromshore
Feeding Gray Whale Distribution
Feeding Gray Whale Sighting Rates
How2015feedinggraywhalesighAngsdifferedfrom2009-2014(Figure4):
• Graywhaleswereconsistentlysightedoffshore65-90kmtotheNNWofWainwrightfromJulytoOctober2015(Figure4,rectangleA).GraywhaleswereseldomseeninthatareainJulyofpreviousyears.
• In2009-2014,graywhalesweredocumentedforagingeastof157.8°W(Figure4,rectangleB),andbeginninginAugust,foragingfartheroffshorebetweenPointFranklinandIcyCapeupto~70kmoffshore(Figure4,rectangleC);graywhaleswereseldomsightedforagingintheseareasin2015.
Figure 2. ForaginggraywhaleSRs,2009-2015,summer(Jul-Aug),fall(Sep-Oct),andseasontotal(Jul-Oct).
Figure 3. ForaginggraywhalemonthlysighAngsoneffortintheeasternChukchiSea,2015and2009-2014.
Figure 4. AreaofhighdensityofforaginggraywhalesighAngsinthenortheasternChukchiSea.On-effort,monthlysighAngsfor2015and2009-2014areshown.AreasofdifferingdistribuAonareshowninrectangleA(2015)andrectanglesBandC(2009-2014).
References • BlanchardAL,FederHM(2014)InteracAonsofhabitat
complexityandenvironmentalcharacterisAcswithmacrobenthiccommunitystructureatmulAplespaAalscalesinthenortheasternChukchiSea.Deep-SeaResII102:132-143.
• SchonbergSV,ClarkeJT,DuntonKH(2014)DistribuAon,abundance,biomassanddiversityofbenthicinfaunainthenortheastChukchiSea,Alaska:RelaAontoenvironmentalvariablesandmammals.DeepSeaResII102:144-163.
• GrebmeierJM,CooperLW,FederHM,SirenkoBI(2006)EcosystemdynamicsofthePacific-influencedNorthernBeringandChukchiSeasintheAmerasianArcAc.ProginOceanogr71:331–361.
JimKopczynskiNOAA/NMFS/AFSC/NMMLNMFSPermitNo.14245FundedbyBOEMIANo.M11PG00033
• Block23inthesouthcentralChukchiSeawasflownonlyin2014and2015.Foraginggraywhaledensityinthisareawasveryhighin2014,buttherewerefewsighAngsin2015(Figure3),possiblyduetolesssurveyeffort.
Experiments,26Aug-7Sepwhichreducedsurveyeffortinsomeareaswheregraywhalesaresightedmostfrequently.
• ThehighestseasontotalSRwasin2012(WPUE=0.0065)(Figure2).
• HighsummerandlowfallSRsofgraywhalesdocumenttheseasonalgraywhalemigraAonsouthoutoftheChukchiSea.
Survey Block 23
Survey Blocks 12-22