Download - Gray Whale Foraging Occurrence in the Northeastern Chukchi Sea…€¦ · Foraging gray whales (Eschrich’us robustus) were documented in the northeastern Chukchi Sea in summer and

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