THE ISSUE. The Bering Sea supports one of the largest, most pro5itable food 5isheries in the world.Commercial5isheriesarethelargestprivate-sectoremployerinAlaska.Theextent,durationandtimingofseaiceadvanceandretreatarechangingdramaticallyinthewarmingArctic,andthisacceleratedtransformationaffectsfoodwebsonwhichcommerciallyimportant5isheriesdepend.IntheeasternBeringSea,theavailabilityanddistributionofsomecommerciallyimportant5ishspeciescurrentlyusedforhumanconsumptiondependsonadequateseaice.

WHY IT MATTERS. Fishing is the core economy for much of coastal Alaska where 5ish harvesting andprocessing oftenprovide the only signi5icant opportunities for private sector employment andwhere 5isheriessupportbusinessesthatprovidepropertyandsalestaxasthelargestsourceoflocalgovernmentrevenueshttp://www.akrdc.org/5isheries. NearlytwomillionmetrictonsofPaci5iccod,walleyepollock,andsalmon,aswellasavarietyofother5in5ishandcrab,areharvestedannuallyfromtheBeringSea,accountingforoverhalfoftotalU.S.harvestvolumeandalmostathirdofU.S.harvestvaluehttp://labor.alaska.gov/trends/nov17.pdf.

Changes in 5ish-stockabundanceanddistributionimpacttheharvests,aswellastheeconomiesofcommunitiesparticipatingintheharvestsandtheirprocessing.Understandingandpredictingthesechangesenablesdecision-makers to adapt 5isheries management strategies, for example, adjusting the total allowable catch of a givenspeciestore5lectitspredictedfutureabundance.

STATEOFKNOWLEDGE.Most5isheriesproductionofthe eastern Bering Sea occurs on the southeastern shelf.Until recent years, the eastern shelf has been reliablycoveredbysea iceduring thecoldseason1. Inaddition toprovidingasurface for icealgae togrow, sea iceover thesoutheasternshelfaffects5ishand5isheriesinmanyways.Ice cover thwarts 5ishing activity from large areas of theshelf inwinter.Thecold(<2°C)water that formson theshelfwhere icehas lingeredandmelteddeterspredatoryadult arrowtooth 5lounder, adult Paci5ic cod, and adultwalleye pollock. Hence, it provides a potential refuge forjuvenile walleye pollock and other forage 5ish moreresistanttothecold2.

Theseaicealsosupportsicealgaeonitsunderside.Thesealgae are an important food for zooplankton in spring.Later, these zooplankton are an important food for thejuvenilesofcommerciallyimportant5ish3,4.Iftheicemeltstoo early, the zooplankton do not get suf5icient ice algae.The 5ishthenhavetoo fewlargezooplanktontoconsumefor nourishment. Recent research has shown a strongcorrelation between the abundance of zooplankton insummerandthesurvivalofharvestable,young-of-the-yearwalleye pollock and Paci5ic cod5,6. Thus, sea-ice-cover inspringislinked,throughzooplankton,totheproductivityofeasternBeringSeapollock5isheries.

AstheeasternBeringSeawarms,seaiceisdeclining.Theproductionofpollock,cod,andpossiblyotherspeciesis likely to diminish. Many temperate species will move northward and become less accessible to 5isheries

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How will diminishing sea ice impact commercial fishing in the Bering Sea?

Figure 1. Spring ice extent in the Bering Sea varies greatly from year to year. 2018 and 2001 had the least ice, 1976 and 2008 the most. Figure courtesy of Phyllis Stabeno, NOAA, Pacific Marine Environmental Laboratory.

based in the southern Bering Sea. However, theability of boreal 5ish species to survive in thenorthernmost Bering Sea and Arctic Oceanmay belimited.Thecold,saltybrinethatresultsfromseaiceformation creates bottomwaters over the northernshelf that are too cold for most 5ish species tosurvive.

WHERE THE SCIENCE IS HEADED. Climateand atmospheric scientists are working to predictthe future climate of the eastern Bering Sea7. Forcommercially important 5ishes, oceanographers aredeveloping models that will permit predictions ofthe amount of young 5ish that will survive toharvestablesizebasedonfutureclimateconditions.Atpresent,modelsarerelativelyskillfulinpredictingthe survivabilityof young-of-the-yearpollockbasedon the amount of large, lipid-rich zooplanktonoverthesouthernBeringSeashelf.Whilepresentabilitytopredicttheabundanceofthesezooplanktonbasedon physical attributes of the ocean is limited,understanding mechanisms affecting theirproductivity is critical for predicting the effects ofsea-ice loss on commercially-important 5isheries,suchasthatforwalleyepollock.

KEYREFERENCES1. Sullivan, M.E., Kachel, N.B., Mordy, C.W., et al. 2014.

Sea ice andwater column structure on the easternBeringSeashelf.Deep-SeaRes.II109:39-56.

2. Mueter, F.J., Litzow,M.A. 2008. Sea ice retreat altersthebiogeographyoftheBeringSeacontinentalshelf.Ecol.Appli.18:309-320.

3. Hunt,G.L., Jr.,Ressler,P.H.,Gibson,G.A., et al. 2016.Euphausiids in theEasternBeringSea:A synthesisof recentstudiesofeuphausiidproduction,consumptionandpopulationcontrol.Deep-SeaRes.II134:204-222.

4. Wang, S.W., Budge, S.M., Iken, K., et al. 2015. Importance of sympagic production to Bering Sea zooplankton asrevealedfromfattyacid-carbonstableisotopeanalyses.Mar.Ecol.Prog.Ser.518:31-50.

5. Eisner,L.,Yasumiishi,E.2017.Largezooplanktonabundanceasan indicatorofpollock recruitment toage-1andage-3inthesoutheasternBeringSea.Pps.145-148,InSiddon,E.,&Zador,S.EcosystemConsiderations:StatusoftheEasternBeringSeaMarineEcosystem.NorthPaci5icFisheryManagementCouncil,Anchorage,AK.

6. Farley, Jr., E.V., Heintz, R.A., Andrews, A.G., Hurst, T.P. 2016. Size, diet, and condition of age-o Paci5ic cod (Gadusmacrocephalus)duringwarmandcoldclimatestatesintheeasternBeringSea.Deep-SeaRes.PartII134:247–254.

7. Hermann,A.J.,Gibson,G.A.,Bond,N.A.,etal.2016.ProjectedfuturebiophysicalstatesoftheBeringSea.Deep-SeaRes.II134:30-47.

Contactsforfurtherinformation:GeorgeL.Hunt,Jr.,UniversityofWashingtongeohunt2@uw.eduLisaEisner,NOAAAlaskaFisherScienceCenter,AukeBayLaboratorylisa.eisner@NOAA.govNeysaM.Call,NationalScienceFoundationncall@nsf.gov

SEARCH Science Brief AA-013. Supported by the National Science Foundation.

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Figure 2. Commercial fish species found in the Bering sea include six species of Pacific salmon, Alaska pollock, Pacific cod, Pacific halibut, yellowfin sole, Pacific Ocean perch and sablefish. Red king crab are also among the types of shellfish found. A healthy, balanced food web contributes to their overall number and distribution throughout the area. Copyright The Pew Charitable Trust, with permission. http://www.pewtrusts.org/-/media/assets/2014/10/ecosystem-based-fishery-management-in-the-bering-sea.pdf