Eastern Bering Sea Report Card - 2021

Eastern Bering Sea 2021 Report Card (pdf)

For more information on individual Report Card indicators, please see `Description of the Report Card indicators' (p. 246). For more information on the methods for plotting the Report Card indicators, please see `Methods Description for the Report Card Indicators' (p. 249). * indicates Report Card information updated with 2021 data.

  • * The North Pacific Index (NPI) effectively represents the state of the Aleutian Low. Above (below) average winter (November-March) NPI values imply a weak (strong) Aleutian Low and generally calmer (stormier) conditions. The NPI was above average during the winter of 2020-2021 before returning to near average again in summer 2021.
  • * The mean sea ice extent across the Bering Sea (1 Aug-31 Jul; western and eastern) exhibited no long term trend, although a steep decline in ice extent was observed from 2012 (highest extent on record) to 2018 (lowest extent on record). The 2020-2021 daily mean extent of 268,748 km2being near the long-term mean . Seasonal sea ice extent has implications, for example, to the cold pool, spring bloom strength and timing, and bottom-up productivity.
  • * The areal extent of the cold pool in the eastern Bering Sea (EBS), as measured during the bottom trawl survey (June-Aug; including strata 82 and 90), has increased since 2018, yet the 2021 extent (58,975 km2) was the 4th lowest on record and remained more than one standard deviation below the grand mean of the time series.
  • * The biomass of aggregate forage fish (i.e., eulachon, Pacific capelin, sand lance species, rainbow smelt, Pacific sandfish, and a group of minor smelt species) declined steeply between 2015 and 2017, and remained below their long term mean in 2021 .
  • * The biomass of motile epifauna measured during the bottom trawl survey (June{Aug) peaked in 2017 and remained above their long term mean in 2021 . Trends in motile epifauna biomass indicate benthic productivity , although individual species and/or taxa may reflect varying time scales of productivity. Collectively, brittle stars, sea stars, and other echinoderms account for more than 50% of the biomass in this guild. The recent (2016{2021) mean biomasses for all three of these functional groups are well above their long term means. The current mean biomasses for all crab functional groups, including hermit crab, king crab, tanner crab, and snow crab are all below their long term means.
  • * The biomass of benthic foragers measured during the bottom trawl survey (June{Aug) is at the lowest level over the times series , more than one and a half standard deviations below 1982{2021 levels. Trends in benthic forager biomass are variable over the time series and indirectly indicate availability of infauna (i.e., prey of these species). Dominant species in the benthic foragers guild include Yellowfin sole and Northern rock sole, both of which are below their long-term means in 2021.
  • * The biomass of pelagic foragers measured during the bottom trawl survey (June{Aug) was generally stable from 2016 to 2019, but dropped in 2021 to their second lowest value over the time series (1982-2021). The trend in the pelagic forager guild is largely driven by Walleye pollock which, on average, account for more than 66% of the biomass in this guild. Trends in pelagic forager biomass indicate availability of forage fish (i.e., prey to upper trophic levels) as well as predator abundance within the ecosystem. In 2021, the survey index for pollock was the third lowest over the time series. With the exception of Pacific herring, the 2021 index for all other species and functional groups in the pelagic forager guild were below their long term means.
  • * The biomass of apex predators measured during the bottom trawl survey (June-Aug) was within normal limits in 2021. Trends in apex predator biomass re ect relative predation pressure on zooplankton and juvenile fishes . The trend in the apex predator guild is largely driven by Pacific cod, whose recent (2016-2021) mean biomass is below their long term mean (1982-2021). In contrast, the current mean biomass of Arrowtooth flounder, Sablefish, and Alaska skate are all above their long-term means.
  • Seafloor habitat impacted by trawls (pelagic and non-pelagic trawl, longline, and pot) as of December 2020 showed interactions have remained below the disturbance levels previous to the implementation of sweep modifications on non-pelagic trawl gear in 2009. However, both pelagic and non-pelagic trawling effort has been at or above average since 2013. This increase, as well as the inclusion of 2003{2014 unobserved fishing events (see p. 202), has resulted in an increase to habitat disturbance . Fishing gear can affect habitat used by a fish species for the processes of spawning, breeding, feeding, or growth to maturity.

*indicates time series updated in 2021 Mean Trend  
*North Pacific Index (Nov-Mar average)
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*Sea Ice Extent
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*Cold Pool Extent
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*Aggregate Forage Fish Biomass
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*Motile epifauna biomass (fish and inverts 1000t)
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*Benthic forager biomass (fish 1000t)
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*Pelagic forager biomass (fish 1000t)
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*Apex predator biomass (fish 1000t)
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Habitat impacted by trawls
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  2017-2021 Mean   2017-2021 Trend
  1 s.d. above mean   increase by 1 s.d. over time window
  1 s.d. below mean   decrease by 1 s.d. over time window
  within 1 s.d. of mean   change <1 s.d. over time window
  fewer than 2 data points   fewer than 3 data points