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Marine Ecosystem - Bering Sea

Overview | Bering Sea | Barents Sea | Greenland

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The Bering Sea in the western Arctic is showing indications that Arctic species which require the presence of sea ice are being replaced by sub-Arctic species that don't require sea ice. An indicator of this shift is that summer water temperatures of the southeast Bering Sea are nearly 2 degrees C warmer in 2001-2003 than 1995-1997 (figure below left), and that ice in this region is leaving earlier (figure below right). Pollock are currently a major economic resource for the Bering Sea. Lack of sea ice tends to favor pollock, which has had a high biomass for the last decade, at the expense of bottom-living fish and crab. The biomass for pollock in millions of tons (diamonds) for Bering Sea, and the number of new fish added each year (recruitment) are shown in in the middle figure below.

Marine mammals are also major consumers of fish and other species in the Bering Sea ecosystem and may also have been impacted by climate shifts. The number of new fur sea pups added to the population on St. Paul Island (in the Pribilof Islands) (bottom figure), shows a decrease after the 1970s and another more recent decrease after 1998. Although it is difficult to assign direct causes to the declines, there was a climate shift in the North Pacific Ocean in 1977, and there has been sustained warming in the 2000s.

Southeast Bering Sea summer ocean temperatures Ice Retreat data
Southeast Bering Sea summer ocean temperatures. From Phyllis J. Stabeno NOAA/PMEL/FOCI.. Ice Retreat Index: Number of days with ice cover after March 15 in the area 56-58°N, 163-165°W. From the Bering Climate website.

Year class strength by year for EBS pollock Bering Sea pollock


Walleye Pollock

Walleye Pollock.
Photo from the NOAA AFSC.

Year-class strengths by year (as age-1 recruits) for EBS pollock from the current model compared with the previous assessment. The horizontal line represents the mean age-1 recruitment for all years since 1964 (1963-2013 year classes). Error bars reflect 90% credible intervals based on model estimates of uncertainty. From 2015 North Pacific Groundfish Stock Assessment and Fishery Evaluation Reports for 2016 Eastern Bering Sea (EBS) pollock spawning stock biomass (SSB) for the 7 preliminary models that simply incrementally add data to the model accepted in 2014 (top) and comparing just two models (with “no new” data (m0.1) and all data added in the 2015 assessment relative to the 2014 assessment (middle panel). The bottom panel compares the model with all new data but using the standard BTS index (m0.6) and the index corrected for trawl efficiency (m0.7). From 2015 North Pacific Groundfish Stock Assessment and Fishery Evaluation Reports for 2016  

Chart of Northern fur seal Callorhinus ursinus pups born on St. Paul
  Image of Northern fur seal Callorhinus ursinus
Northern fur seal Callorhinus ursinus pups born on St. Paul in the Pribilof Islands. Error bars are approximate 95% confidence intervals. From NOAA NMFS AFSC.   Northern fur seal Callorhinus ursinus. From the NOAA Photo Library.

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