Gray Whale Foraging Occurrence in the Northeastern Chukchi Sea…€¦ · Foraging gray whales...
1
Overview Foraging gray whales (Eschrich’us robustus) were documented in the northeastern Chukchi Sea in summer and fall 2015 by the Aerial Surveys of ArcAc Marine Mammals (ASAMM) project. ASAMM line transect surveys, conducted by the Marine Mammal Laboratory and funded and co-managed by the Bureau of Ocean Energy Management, were conducted in the eastern Chukchi Sea, 67°-72°N and 155°-169°W, from July through October 2009-2015. The northeastern Chukchi Sea is an important foraging and weaning ground for gray whales. They typically begin to arrive in the northeastern Chukchi Sea in June and July, feed heavily in July and August, and migrate south in September and October. Feeding gray whales accounted for 58% of the total gray whales sighted on effort in 2015, similar to 2009-2014 (50-76% of total gray whales sighted on effort per year). Feeding gray whale sighAng rate (SR, number of whales on effort per km flown) in summer 2015 was higher than summer SRs in 2009-2014, but fall 2015 SR was lower than the mean fall SR from 2009-2014. Gray whales were sighted foraging predominantly between Point Barrow and Icy Cape, similar to 2009-2014. However, compared to previous years, gray whales in 2015 were sighted farther offshore in July, were not sighted as far offshore between Point Franklin and Icy Cape, and were not sighted east of 157.8°W. Discussion • The differences in distribuAon and relaAve abundance from 2015 and previous years could be due to changes in prey distribuAon resulAng from changing hydrographic condiAons and oceanic producAvity or from intense feeding by gray whales. • Gray whales documented in the Chukchi Sea overlay areas of dense benthic amphipod communiAes (Blanchard and Feder 2014, Schonberg et al. 2014), and it is assumed that gray whales associated with mud plumes in this area are feeding on this prey. • As global climate change accelerates and mulA-year sea ice conAnues to melt, benthic-dominated ecosystems of the Bering and Chukchi seas may become pelagic-dominated (Grebmeier et al. 2006). • Gray whales have a flexible and opportunisAc foraging strategy and may shi_ their foraging habits from the benthic- to the pelagic- dominated ecosystem. • The spaAal, temporal, and interannual changes in gray whale foraging distribuAon and relaAve abundance highlight the need for conAnued broad-scale aerial surveys each summer and fall. Acknowledgements: This study is funded and co-managed by the Bureau of Ocean Energy Management and NOAA (IA No. M11PG00033) and was supported Carol Fairfield (BOEM COR). At MML, addi’onal support was provided by Robyn Angliss, Stefan Ball, Phil Clapham, Nancy Friday, Kim Shelden, Janice Waite, and administra’ve personnel. At JISAO, support was provided by Amy Kennedy and administra’ve personnel. In addi’on to the authors, numerous dedicated biologists have par’cipated in these surveys. Clearwater Air, Inc. pilots safely navigated us through the skies. Real-’me flight following via satellite link was provided by Department of Interior personnel. Programming support was provided by Mike Hay (Xera GIS). Without all of these people, our surveys would not have been possible; our sincerest thanks to all! The views expressed or implied here are those of the authors and do not reflect the posiAons of the NaAonal Marine Fisheries Service, NaAonal Oceanic and Atmospheric AdministraAon, or Department of Commerce. Figure 1. ASAMM on-effort survey flightlines, 2015. Methods & Survey Effort Amelia Brower, Amy Willoughby– Joint InsAtute for the Study of the Atmosphere and Ocean, University of Washington, [email protected] Janet Clarke– Leidos Megan Ferguson – Marine Mammal Laboratory, Alaska Fisheries Science Center, NMFS, NOAA Gray Whale Foraging Occurrence in the Northeastern Chukchi Sea, Summer and Fall 2015 • Line transect aerial surveys • Twin engine turboprop aircra_ • 2 July – 30 October 2015 • 1200 _ (366 m) in the Chukchi Sea • 1500 _ (457 m) in the Beaufort Sea • Survey effort: “on-effort” (transect and circling from transect), “off- effort” (search and circling from search), or deadhead • ~34,300 km flown on effort in survey blocks 12-22 in 2015 (Figure 1). • SighAng Rate (SR): Number of on-effort feeding whales per on-effort kilometer surveyed (whales per unit effort, WPUE). • 2015 had the highest summer SR (WPUE = 0.0120) (Figure 2), despite poor weather that reduced survey effort in July. • Fall 2015 SR (WPUE = 0.0013) was lower than the Fall SR in some previous years (Figure 2) and lower than the mean SR from 2009-2014 (mean WPUE = 0.0016), possibly due to differing survey protocols during the ArcAc Aerial CalibraAon In 2015, foraging gray whales sighted on effort in all months were documented predominantly in water <55 m deep in these areas (Figure 3): • Point Barrow to Point Franklin 10-30 km from shore • NNW of Wainwright 25-40 km and 65-90 km from shore Feeding Gray Whale Distribution Feeding Gray Whale Sighting Rates How 2015 feeding gray whale sighAngs differed from 2009-2014 (Figure 4): • Gray whales were consistently sighted offshore 65-90 km to the NNW of Wainwright from July to October 2015 (Figure 4, rectangle A). Gray whales were seldom seen in that area in July of previous years. • In 2009-2014, gray whales were documented foraging east of 157.8°W (Figure 4, rectangle B), and beginning in August, foraging farther offshore between Point Franklin and Icy Cape up to ~70 km offshore (Figure 4, rectangle C); gray whales were seldom sighted foraging in these areas in 2015. Figure 2. Foraging gray whale SRs, 2009-2015, summer (Jul- Aug), fall (Sep-Oct), and season total (Jul-Oct). Figure 3. Foraging gray whale monthly sighAngs on effort in the eastern Chukchi Sea, 2015 and 2009-2014. Figure 4. Area of high density of foraging gray whale sighAngs in the northeastern Chukchi Sea. On-effort, monthly sighAngs for 2015 and 2009-2014 are shown. Areas of differing distribuAon are shown in rectangle A (2015) and rectangles B and C (2009-2014). References • Blanchard AL, Feder HM (2014) InteracAons of habitat complexity and environmental characterisAcs with macrobenthic community structure at mulAple spaAal scales in the northeastern Chukchi Sea. Deep-Sea Res II 102:132-143. • Schonberg SV, Clarke JT, Dunton KH (2014) DistribuAon, abundance, biomass and diversity of benthic infauna in the northeast Chukchi Sea, Alaska: RelaAon to environmental variables and mammals. Deep Sea Res II 102:144-163. • Grebmeier JM, Cooper LW, Feder HM, Sirenko BI (2006) Ecosystem dynamics of the Pacific-influenced Northern Bering and Chukchi Seas in the Amerasian ArcAc. Prog in Oceanogr 71:331–361. Jim Kopczynski NOAA/NMFS/AFSC/NMML NMFS Permit No. 14245 Funded by BOEM IA No. M11PG00033 • Block 23 in the southcentral Chukchi Sea was flown only in 2014 and 2015. Foraging gray whale density in this area was very high in 2014, but there were few sighAngs in 2015 (Figure 3), possibly due to less survey effort. Experiments, 26 Aug- 7 Sep which reduced survey effort in some areas where gray whales are sighted most frequently. • The highest season total SR was in 2012 (WPUE = 0.0065) (Figure 2). • High summer and low fall SRs of gray whales document the seasonal gray whale migraAon south out of the Chukchi Sea. Survey Block 23 Survey Blocks 12-22
Transcript of Gray Whale Foraging Occurrence in the Northeastern Chukchi Sea…€¦ · Foraging gray whales...
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
