occurrence of humpback, fin, and minke whales in the eastern … · 2016-03-15 · fin whales (41...

AbstractSightingsofhumpback(Megaptera novaeangliae), fin(Balaenoptera physalus)andminke (Balaenopteraacutorostrata)whalesweremadeduringtheAerialSurveysofArcticMarineMammals(ASAMM)project,fundedbyBOEMandco-managedbyBOEMandNOAA.SurveyswereconductedintheeasternChukchiSea(67°-72°N,157°-169°W)fromJulythroughOctober,2008-2015,inastudyareathatencompassedoffshoreoilandgasleasesintheChukchiSeaPlanningAreaandshippinglanesinthesouthernChukchiSea.Approximately186,000kmoneffortwasflowntodocumentrelativeabundance,spatialandtemporaldistribution,andbehaviorofmarinemammals.Finwhales(41sightingsof67whales)hadthemostlimiteddistribution,from67°Nto69.5°N,andwereseenprimarilyinAugustandSeptember.Humpbackwhales(55sightingsof97whales)weredistributedfrom66.9°Nto71.2°N,andwereseenprimarilyinSeptember.Minke whales(24sightingsof27whales)hadthemostextensivedistribution,from67.1°Nto71.9°N,andwereseenfromJulythroughSeptember.Fin,humpback,andminke whaleswereoftenseenincloseassociationwithothercetaceanspecies,includinggraywhales.Behaviorsobservedincludeddiving,feeding,milling,resting,rolling,swimming,andtailslapping.Finwhalecalves(2)wereseenin2012;humpbackwhalecalveswereseenin2014(1)and2015(1).Fin,humpbackandminke whalesareknowntohaveoccurredhistoricallyinthePacificArctic,particularlyneartheChukotkaPeninsula,andrecentvisualandacousticdetectionssuggestthatuseofthisareamaybeincreasing.Duringaerialsurveysconductedfrom1979-1991inthissamearea,therewas1sightingof3finwhales;however,surveyeffortwassporadicamongyears,andmostsurveyeffortoccurredinOctober.Increasedoccurrencemaybeduetoeachpopulation’sabundanceandrangerecoveringfromcommercialwhalingthatoccurredasrecentlyasthe1970s,butmayalsoreflectanincreaseinmarinemammalresearchintheareaorresponsestoongoingclimatechange. (AbstracthasbeenupdatedtoreflectsightingsfromOctober2015.)

Summary, 2008-2015

Comparison with ASAMM 1979-1991§ Sightingslimitedto1sightingof3finwhales(July1981)(Figure1)§ SurveyeffortwasordersofmagnitudelessexceptinOctober(Figure4)

Discussion§ Fin,humpback,andminke whalesoccurinthenorthernBeringSea(Mooreetal.,2002)andthereisampleevidenceofhistoricaloccurrenceinthe

westernChukchiSea,buttherearerelativelyfewrecordsfortheeasternChukchiSea(summarizedinClarkeetal.,2014).§ IncreasinglycommonoccurrenceoftheselargewhalesintheeasternChukchiSeainrecentyears(2008-present)hasbeendocumentedbythisstudy

andcorroboratedbyconcurrentvisualandacousticstudies(e.g.,CSESP,ARCWEST,CHAOZ,Shell).§ PopulationsmayberecoveringfromillegalcommercialwhalingthatoccurredintheNorthPacificasrecentlyasthe1970s(Ivashchenkoetal.,2013).§ Distributionoftheselargewhalesmayalsoberelatedtowatermassesthatcollectivelyproducesharptemperatureandsalinitygradients(Eisneretal.,

2013),whichcanaggregatezooplankton,fishesthatfeedonzooplankton,andlargewhalesthatfeedonfishes.Variationsin watermassincursion,combinedwithearlierandgreaterlossofsummerseaiceandothereffectsofclimatechange,maybeenhancingtheabilityof largewhalestoexpandfurtherintotheChukchiSea.

§ Finally,thepotentialeffectofincreasedsurveyeffortcannotbeignored.Mostfin,humpback,andminke whaleswereseen(andsightingrateswerehighest)inAugustandSeptember2008-2015.SurveyeffortduringAugustandSeptember1979-1991wasnotextensive,particularly inAugust(Figure4).SurveyeffortinOctober1979-1991actuallyexceededthatforOctober2008-2015.However,October2008-2015hadthelowest sightingrates,indicatingthatfin,humpback,andminke whalesmaybemigratingsouthfromtheChukchiSeabythattime.ItispossiblethatlargewhaleswerepresentintheeasternChukchiSea,particularlythesouthcentralsubarea,in1979to1991butnotdetectedduetoinfrequent surveyeffortduringthemonthstheywouldmostlikelyhaveoccurred.

TherecommendationsandgeneralcontentpresentedinthisposterdonotnecessarilyrepresenttheviewsorofficialpositionoftheDepartmentofCommerce,theNationalOceanicandAtmosphericAdministration,ortheNationalMarineFisheriesService.

Figure 1. EasternChukchiSeastudyareawithfin,humpback,andminke whalesightings,July-October2008-2015,andonefinwhalesighting,July1981.Allsightingsareplotted,regardlessofsurveymode;on-effortsightingsbyprimaryobserversaredesignatedwithastar.Eachsightingmaybeofoneormorewhales.ThenortheasternChukchiSeasubareaisoutlinedinmagenta;thesouthcentralChukchiSeasubareaisoutlinedinumber.

Figure 2. Fin,humpback,andminke whalesightingratespermonth,easternChukchiSea, 2008-2015.Sightingrate,usingsightingsbyprimaryobserverscollectedonlyduringon-effortsurveys,providesanestimateofrelativeabundance.

Figure 4. SummaryofASAMMeffortintheeasternChukchiSea,1979-1991and2008-2015.Effortfrom1992to2007wasnegligible.

Figure 3. Fin,humpback,andminke whalesightingratesforthenortheasternChukchiSeaandsouthcentralChukchiSeasubareas,July-Octobercombined,2008-2015.Sightingrate,usingsightingsbyprimaryobserverscollectedonlyduringon-effortsurveys,providesanestimateofrelativeabundance.

Methods§ EasternChukchiSeastudyarea,67°-72°N,157°-169°W(Figure1)§ Linetransectaerialsurveys§ Twinturboprop,highwingaircraft§ 1200ft (366m)surveyaltitude§ Flyeveryday,weatherpermitting,2Julythrough30October§ Twoprimarymarinemammalobservers,onedatarecorder§ Surveymodesincludeon-effort(transectandcirclingfromtransect)

andoff-effort(searchandcirclingfromsearch)§ CircleonmostcetaceansightingstogetpositivespeciesID,

determinegroupsize,andlookforcalves

Janet Clarke – Leidos,janet.clarke@leidos.com Megan Ferguson – MarineMammalLaboratory,AFSC,NMFS,NOAAAmelia Brower, Amy Willoughby, and Christy Sims – JointInstitutefortheStudyoftheAtmosphereandtheOcean

Results

Table 1. Summaryofkeyresultsbasedonallsightings,regardlessofsurveymode(exceptasnoted).Maximumvaluesboldedanditalicized.

Humpbackwhale,September2014;photobyLeahCrowe,NMFSPermitNo.14245

1 Figure1;2 Figure2;3 Figure3;4 basedonsightingsbyprimaryobserversduringon-effort surveys

Occurrence of Humpback, Fin, and Minke Whales in the Eastern Chukchi Sea, 2008-2015: Population Recovery, Response to Climate Change, or Greater Effort?

Finwhale,July2013;photobyVickiBeaver,NMFSPermitNo.14245

References Clarke,J.,K.Stafford,S.E.Moore,B.Rone,L.Aerts,andJ.Crance.2013.SubarcticcetaceansinthesouthernChukchiSea:Evidenceofrecoveryorresponsetoachangingecosystem.Oceanography 26(4):136–149.

Eisner,L.,N.Hillgruber,E.Martinson,andJ.Maselko.2013.PelagicfishandzooplanktonspeciesassemblagesinrelationtowatermasscharacteristicsinthenorthernBeringandsoutheastChukchiseas.PolarBiology36:87-113.

Ivashchenko,Y.V.,P.J.Clapham,andR.L.Brownell,Jr.2013.SovietcatchesofwhalesintheNorthPacific:revisedtotals.J.CetaceanRes.Manage.13(1):59-71.

Moore,S.E.,J.M.Waite,N.A.Friday,andT.Honkalehto.2002.Cetaceandistributionandrelativeabundanceonthecentral-easternandsoutheasternBeringSeashelfwithreferencetooceanographicdomains.Progress inOceanography55:249-261.

Acknowledgements: Thisstudywasfundedandco-managedbytheBureauofOceanEnergyManagement(IANos.M11PG00033andM08PG20023),whereweappreciatedthesupportofJeffDenton,CarolFairfield,ChuckMonnett,andDeeWilliams.AtAFSC,additionalsupportwasprovidedbyRobynAngliss,PhilClapham,StefanBall,NancyFriday,KimShelden,JaniceWaite,andadministrativeandtravelpersonnel. AerialsurveysweresafelyandexpertlyflownbyNOAAAircraftOperationsCenter,CommanderNorthwest,andClearwaterAir.Oursincereappreciationtothededicatedandprofessionalmarinemammalobserverswhosuited-upandcontortedtheirbodiesintobubblewindowsforseveralhoursatatime.Real-timemonitoringviasatellitetrackingofsurveyflightswasprovidedbyUSDOI.WearealsogratefulfortheanalyticalandprogrammingexpertiseofMikeHay(Xera GIS).AFSCGraphicsassistedwiththeposterdesign.

Finwhale Humpbackwhale Minke whale

EasternChukchiSeaMonthsofoccurrence JulytoOctober1 JulytoOctober1 JulytoSeptember1

Relativeabundance4 0.00032 0.00052 0.00012

Distribution 67°Nto69.5°N1 66.9°Nto71.2°N1 67.1°Nto71.9°N1

Depthrange 28to52m 7to61m 3to60mDistancefromshorerange 24to140km 1to145km <1to170km

NortheasternChukchiSubareaMonthsofoccurrence JulytoAugust1 JulytoAugust1 JulytoSeptember1

Relativeabundance4 0 3 <0.00013 0.00013

Depthrange 28to33m 7to55m 3to60mDistancefromshorerange 42to75km 1to89km <1to170km

Southcentral ChukchiSeaSubareaMonthsofoccurrence JulytoOctober1 AugusttoOctober1 AugusttoSeptember1

Relativeabundance4 0.00433 0.00543 0.00043

Depthrange 33to52m 15to61m 24to38mDistancefromshorerange 24to140km 4to145km 8to114km