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Ecosystem Considerations 2017 Status of the Eastern Bering Sea Marine Ecosystem
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2017
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Description:The eastern Bering Sea was characterized by moderately warm conditions in 2017. The PDO remained positive, although the magnitude decreased. Weak La Niña conditions are predicted for the winter of 2017-2018. Sea ice extended over the southern shelf during the winter and spring and resulted in an extensive, although narrow, cold pool during summer 2017. Acoustic estimates of euphausiids from the 2016 summer trawl survey were the lowest in the time series. RZA assessments showed comparable euphausiid abundances over the middle shelf between 2016 and 2017. The biomass of motile epifauna remains above the long-term mean, with an increasing trend in the past 5 years. Brittle star biomass remains above average, with a slight (9%) decline from 2016–2017. Urchins, sand dollars, and cucumbers are also above their long-term mean, with a 12% increase from 2016–2017. King and tanner crabs decreased (28% and 21%, respectively). The biomass of benthic foragers dipped in 2015, but has remained at a near-average level in2016 and 2017. The decline in 2015 was due to a 25% decline in Northern rock sole, which continued to decline in 2017 (by 7.5%). The overall return to an average level was due to a 112% increase in “miscellaneous flatfish” (e.g., Bering flounder, Longhead dab, Slender sole, Starry flounder) and 24% increase in Flathead sole between 2016 and 2017. The biomass of pelagic foragers remains at its 34-year mean in 2017. A large increase in Pacific herring was off-set by a decrease in Capelin. The biomass of fish apex predators declined, largely driven by a 35% reduction in Pacific cod biomass and 11% reduction in Arrowtooth flounder biomass. The multivariate seabird breeding index remains below the long term mean, indicating that seabirds bred later and less successfully in 2017. Seabirds showed overall poor reproductive success at St. Paul and St. George Islands in 2017, with the exception of red-faced cormorants. Northern fur seal pup production for St. Paul Island in 2016 remained low with a decrease of 12.1% from 2014. Pup production on St. George Island increased 8.2% between 2014 and 2016. Seafloor habitat disturbance due to fishing gear (pelagic and non-pelagic trawl, longline, and pot) shows interactions have remained below the long-term average since 2011.
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Rights Information:Public Domain
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