UNDERSTANDING ECOSYSTEM PROCESSES IN THE BERING SEA 2007–2013

Whales and Porpoise in the Bering Sea CHANGES WITH TEMPERATURE

The Bering Sea has gone through in 2002, 2008 and 2010 on the east- estimate abundance and to evalu- significant environmental changes ern Bering Sea shelf. When we saw a ate whether numbers changed over over the past decades, some of group of cetaceans, we recorded the time. We computed the abundance which may be driven by global location, the species and the number of these species by estimating how warming. Understanding distribu- of individuals. We plotted sight- many groups were seen within a tion and abundance is important for ings to examine the distribution of certain distance from the ship and evaluating how these changes will each species. Five cetacean species extrapolating to the whole survey influence the habitat and behavior (humpback, fin and minke whales, area. Finally, we estimated changes in of cetaceans (whales, dolphins and Dall’s and harbor porpoise) were abundance between 2002 and 2010 porpoise). Also, because year-to- seen in sufficient numbers to also using traditional regression methods. year variation in ocean temperatures continued on page 2 and productivity has been shown to Fig. 1 affect their prey of zooplankton and 2002 (Warm) 2008 (Cold) 2010 (Cold) Trend schooling fish, determining how 231 436 675 12.0% cetaceans interact with their envi- Humpback Whales (39 to 1370) (177 to 1073) (150 to 3040) (-9.8% to 34.0%) ronment will help predict how they 419 1368 1061 14.0% will respond to these changes. Fin Whales (219 to 802) (695 to 2692) (493 to 2283) (1.0 to 26.5%) Our study shows that the abun- 389 517 2020 15.6% dance and distribution of cetaceans Minke Whales (147 to 1030) (146 to 1831) (520 to 7855) (-6.2% to 38.6%) changed with the temperature of 35,303 14,543 11,143 -14.4% the environment. In colder years, Dall’s Porpoise (12,989 to 95,946) (7598 to27,837) (5788 to 21,451) (-29.0% to 1.0%) there were more whales and fewer 1971 4056 833 -0.7% Harbor Porpoise (798 to 4870) (1844 to 8920) (230 to 3018) (-33.6% to 24.9%) porpoise in our study area (Figure 1). The distributions of humpback Estimated abundance by species and year, with 95% confidence intervals in parentheses. (Megaptera novaeangliae) and fin whales (Balaenoptera physalus) were similar regardless of temperature, The Big Picture but the distributions of minke We examined the Bering Sea Project hypothesis that climate and ocean conditions will whales (B. acutorostrata), Dall’s affect cetacean prey and, consequently, will influence cetacean foraging habits. Will whales (Phocoenoides dalli) and harbor remain in their typical feeding areas in years when their prey is not as abundant? Because porpoise (Phocoena phocoena) other studies have found that prey populations change with ocean temperature, we use seemed to shift toward deeper temperature as a proxy for change in cetacean prey and foraging habitats. We examined the waters in colder years (Figure 2). distribution and quantified the abundance of whales and porpoise in warm and cold years and by oceanographic domain. Our conclusion: the abundance of whales increased in cold years, How We Did It which corresponds to periods when higher abundance of their potential prey seems to occur As part of NOAA’s walleye pol- as revealed by other Bering Sea Project studies on zooplankton and fish. The abundance of lock (Gadus chalcogrammus) assess- porpoise decreased in cold years, but the reasons are not yet fully understood. ment cruises, we conducted surveys

WHALE BROAD-SCALE DISTRIBUTION A component of the BEST-BSIERP Bering Sea Project, funded by the National Science Foundation and the North Pacific Research Board with in-kind support from participants. Study. www.nprb.org/beringseaproject National Science Foundation’s Bering Ecosystem Integrated Ecosystem Research Program andthe the North Pacific Research Board’s Bering Sea The Bering Sea betweenProject isapartnership preting future changes. forinter population size isnecessary on current cetaceanoccurrence and Sea. For thisreason, information warmer conditionsintheBering change causesprolonged periodsof like whalesare expectedifclimate dance oflargemarinepredators on thedistributionandabun- their prey changes.Profound effects composition andenergeticvalue of intimeand space ifthe will vary ceans andtheirpreferred habitats suspect thattheabundanceofceta- the distributionoftheirprey. We Sea, isassumedtobedriven by high latitudes,includingtheBering Why We Did It remained constant. abundance ofporpoisedeclinedor over thestudyperiod,but dance ofbaleenwhalesincreased We foundevidencethattheabun- both outerandmiddledomains. and harborporpoisewere foundin more commonintheoutershelf Bering Sea. Dall’s porpoisewere scattered throughout theeastern tinental shelf. Minke whaleswere occurred primarilyintheoutercon- the AlaskaPeninsula andfin whales concentrated incoastalwatersalong What WeFound Phillip J. Clapham, NOAA AFSCNMML Ecosystems Division Moore, E. Sue NOAA, Science of Office & Technology, Marine Janice M. Waite, NOAA AFSCNMML Collective Alexandre N.Zerbini, NOAA AFSCNMMLandCascadia Research National MarineMammalLaboratory (NMML) A.Friday,Nancy NOAA Fisheries Alaska Center Science (AFSC), The distributionofcetaceansin Humpback whaleswere more A component oftheBEST-BSIERP Project, Sea Bering funded by the National Science Foundation from Pacific participants. support Research andtheNorth Board with in-kind - Fig. 2 2008, green for 2010. ofthefiveSightings cetacean inthestudyarea, species by year—red dots for 2002,blue for WHALE BROAD-SCALE DISTRIBUTION Humpback Whale Harbor Porpoise Dall’s Porpoise Minke Whale Fin Whale

National Park Service Kate Stafford Gerry Sanger Dave Ellifrit Dave Ellifrit