Overview• Northern fur seals (NFS; Callorhinus ursinus)

breeding on the Pribilof or Bogoslof Islands in the Bering Sea account for the majority of worldwide pup production in this species1.

• NFS from these two sites undergo an annual migration of ~8 mo. in late autumn, winter, spring.

• Different NFS groups face different pressures:• Reproductive males must acquire energy stores

to fast and hold territories on land the following summer;

• Pregnant adult females must acquire resources for fetal growth prior to giving birth after the migration;

• Newly-weaned pups face winter storms, large waves, declining sea and air temperatures on their first migration, but are of much smaller size than adults and lack experience.

• In a typical year, more than half of these pups do not survive2.

• Over the past two decades, the Alaska Ecosystems Program at the NOAA National Marine Mammal Laboratory has engaged in extensive satellite tracking of Bering Sea NFS in order to better understand habitat requirements and foraging strategies during the migratory period.

• Here, key findings from published and ongoing studies are summarized.

MethodsNational Marine Mammal Laboratory researchers

equipped 256 NFS (135 pups, 106 adult females, 15 adult males) from the Pribilof and Bogoslof Islands with satellite-telemetery tags capable of providing animal location estimates, and in some cases, dive data.

Location data were fit with a switching state-space movement model. Movement and dive behavior were compared to remotely sensed data, atmospheric reanalysis, autonomous in situ ocean sampling, and animal-borne temperature and salinity data. These procedures are described in Sterling et al.3 and Pelland et al.4

Behavioral responses to environmental features suggest that the latter influence prey fields, and/or NFS condition, and potentially demography.• Resultssuggestwindscouldinfluencea)pupdispersalpatternsandb)availabilityofresourcesthroughforcedchangesinupper-oceanstratification.Thesefactorsmayberelevanttounexplainedlarge

interannual variationsinpupsurvivorshipandarethesubjectofongoingstudy.• Basin-scaleinterannual variability(e.g.,PDO,ENSO)affectswinds,upper-oceanstratification,andecosystemproductivityandplaysanunknownroleinBeringSeaNFSdemography,butisofgreatsignificance

toSanMiguelNFSbreedingintheCaliforniaCurrentSystem.• Observationsoverthepast50yr indicatechangesincharacterofannualcycleofwaveheightsinNorthPacificOcean,andapoleward shiftinthemidlatitude stormtrack.Ongoingworkisinvestigatingthe

impactofthesetrendsonNFSdemographyduringthisperiod.

References: 1U.S. Department of Commerce (2007). Conservation Plan for the Eastern Pacific Stock of Northern Fur Seal (Callorhinus ursinus). Juneau, AK: National Marine Fisheries Service.2Lander, R.H. (1979) Fishery Bulletin 77(1):311:314.3Sterling, J.T., et al. (2014) PLoS ONE 9(4):e93068 doi:10.1371/journal.pone.0093068.4Pelland, N.A. et al. (2014) PLoS ONE 9(8):e101268 doi:10.1371/journal.pone.0101268.

Acknowledgements: TheauthorswouldliketothankRodTowell,JimThomason,BrianFadely,CareyKuhn,TomGelatt,andKateTowell fortheirfieldeffortsincapturingandinstrumentingnorthern furseals.Northern fursealresearchwasperformedunderNationalMarineMammalLaboratoryPermitNo.782170800,withadditionalfundingcontributionsfromtheNorthPacificResearchBoard,NOAA,theNationalCooperativeResearchProgramoftheNOAAFisheriesOfficeofScienceandTechnology,andtheJointInstitutefortheStudyoftheAtmosphere andOceanattheUniversityofWashington.

TherecommendationsandgeneralcontentpresentedinthisposterdonotnecessarilyrepresenttheviewsorofficialpositionoftheDepartmentofCommerce,theNationalOceanicandAtmosphericAdministration,ortheNationalMarineFisheriesService.

Figure 1. Migratorytracksof256satellite-taggedBeringSeaNFS.Oct-December(toppanel),January-March(middle),April-July(bottom).GreencontourindicatesTransitionZoneChlorophyllFront(TZCF).

NFS migrate to different regions depending on their age and/or sex.

Noel Pelland, Jeremy Sterling, Devin Johnson, Rolf Ream – NationalMarineMammalLaboratory,AlaskaFisheriesScienceCenter,NMFS,NOAAAlan Springer – UniversityofAlaska,FairbanksSara Iverson – DalhousieUniversityMary-Anne Lea – UniversityofTasmania Nicholas Bond – JointInstitutefortheStudyoftheAtmosphereandOcean Charles Eriksen, Craig Lee – UniversityofWashington

Satellite tagging, remote sensing, and autonomous vehicles reveal interactions between foraging and migration behaviors of a top marine predator and the environment in the North Pacific Ocean

Thishadbeenshownpreviouslybutwithdifferentsexes/agesinseparateyears.Ithasprobablybeenknownintraditionalhistoricalknowledgeformillenia.

These groups face differing environmental conditions.

Inparticular,mostadultfemalesandsomepupsmigratetoproductiveeasternboundarycurrentsthat,comparedtotheinteriorNorthPacific,haveashallowermixed-layerdepth(MLD),fewerhigh-winddays(Fig.2),andtopographicfeatureswhereeddygenerationiscommon4.

Despite this, adults have similar diving behavior.

Adultmalesdivedduringalltimesofdayandtothebaseofthemixedlayerorbelowduringdaytime3(e.g.,Fig.3).FemalesenteringtheCaliforniaCurrentexhibitedsimilarpatterns4 inaregionofshallowerMLDs(Fig.4).CorrelationwiththeMLDimpliesthatupper-oceanstratificationaffectsthedepthofNFSpreyfields3,4.

NFS of all groups respond to the wind.

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PupsAdult Females

Atverylowwinds,adultfemalesshowatravelpreferencetotheSEcomparedtopups(Fig.6),likelyreflectingpriorknowledge/experience.

Highwindwasassociatedwithdecreasingarea-restrictedsearchandincreasedtransitforallgroups(Fig.7).NFStravelcorrelateswithwinddirectionandspeed,beingonaveragedownwindandtotheright(Fig.5).

Results are consistent with large differences in size and experience between adults and pups, and in size between sexes.

NFSmasscorrelateswithmaximumdivedepthandsizewiththeabilitytowithstandcoldtemperatures.

Largeradultmales:• Havedivedepthsthatcorrelatewithdeep,

interiorMLDs,• Exhibitmovementsthatareleastcorrelatedwith

thewind,and• Initiateconsistentresidentbehaviorearliestinthe

winter(Fig.7).Theyarefollowedbysmalleradultfemales,andlaterbythestill-smallerpups(Fig.7).

Weconclude3 that:• Adultfemalesareconstrainedbytheirphysical

characteristicstomigratetotemperate,productiveeasternboundarycurrents(predictableandaccessiblepreyresources).

• Adultmalesdonotfacethesesameconstraints,andavoidpredationandcompetitionbyforagingintheinteriorNorthPacificOceanandsouthernBeringSea.

Figure 2. Proportionofhigh-wind(>11ms-1)6hrperiodsinJanuary-March,NCEPReanalysis1,1991-present.ContoursareclimatologicalMLDforthesemonthsfromArgoarray.

Figure 3. ExampledivingrecordfrommigratoryadultmaleNFS3.(Left)Mean6hrdivedepthvs.time;6hrperiodscoloredbytimeofday.BlacklineshowsMLDfromanimal-bornesensors.(Right)Horizontaltrack.

Figure 4. (top)ClimatologicalMLD(dots)andsalinity(colors)inWashingtoncoastaltransitionzonefromautonomousunderwatergliders.(bottom)AdultfemaleNFSmean6hrdivedepth(circles)andclimatologicalchlorophyll(colors).BlacklinesshowgeneralizedadditivemodelfittoMLD/diving4.

Figure 5. MeanNFStravel(vectors),rotatedintodownwind-crosswindcoordinatesystembasedonNCEPReanalysis1windsinterpolatedtoanimallocation.(left)Pups,(center)adultfemales,(right)adultmales.Meantravelcomputedinfivebinsbasedonwindspeed(rows).Whiskersare95%Student’s-t confidenceboundsonmeantravel.

Figure 6. Histogramoftravelbearingforpup(blue)andadultfemale(red)NFSduringOct.-Jan.atverylowwindspeeds(<3ms-1),wherewindeffectontravelisweak.WhiskersareRMSconfidenceboundsonbinproportion.

Figure 7. Ribbonplotsshowlinearmixed-modelbehavioralstateresponseduetodayssince1October(x-axis)andduetowindspeed(ribboncolors),foradultmales(top),adultfemales(middle),andpups(bottom).Highbehavioralstatecorrespondstoresident,area-restrictedsearchmovement.

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