Eastern Bering Sea Report Card - 2023

Eastern Bering Sea 2023 Report Card (pdf)

For more information on individual Report Card indicators, please see ‘Description of the Report Card indicators’ (p. 218). For more information on the methods for plotting the Report Card indicators, please see ‘Methods Description for the Report Card Indicators’ (p. 222).
* indicates Report Card information updated with 2023 data.

  • *The North Pacific Index (NPI) effectively represents the state of the Aleutian Low Pressure System. Above average winter (Nov-Mar) NPI values imply a weak Aleutian Low and generally calmer conditions. The NPI was above the average during winter 2022-2023. The systematically above-average state of the NPI (i.e., weak Aleutian Low) is consistent with the overall decline in the PDO during the interval (see Figure 4).

  • *The mean sea-ice extent across the Bering Sea exhibited no long-term trend 1980–2013 (ice year is defined as 1 August to 31 July; western and eastern). Since 2014, average sea ice extent has generally been near or below the lowest year prior to 2014. The 2023 extent of 243,431 km2was about 15% lower than the 2022 average extent and more than 20% below the 1980 to 2013 median. Seasonal sea-ice extent has implications for the cold pool, spring bloom strength and timing, and bottom-up productivity.

  • *The areal extent of the cold pool in eastern Bering Sea (EBS), as measured during the bottom trawl survey (Jun-Aug; including strata 82 and 90; 1982–2023), increased from the time series minimum in 2018 through 2022. The 2023 extent (179,550 km2) was similar to 2022 and near the time series average.

  • *The proportion of open water blooms in the southeastern Bering Sea (SEBS) was about 50% during 2023, which is lower than during the warmer period 2014–2021, but higher than during the cold period 2007–2012.

  • *The abundance of large copepods (predominantly Calanus spp.) as measured during August/September along the 70m isobath over the southern shelf, peaked in 2008 and 2012 during cold years, but has remained below the time series (2000–2023) mean since 2015.

  • An acoustic estimate of euphausiid density was below average in 2022 (2004–2022), but remained greater than the lowest point in the time series that occurred in 2016.

  • The biomass of pelagic forage fish (i.e., age-0 pollock, age-0 Pacific cod, herring, capelin, and all species of juvenile salmonids) sampled by surface trawl in late-summer (Aug-Sep; 2003–2022) peaked in 2004 and 2005, was below the time series average from 2006–2012, was above average in 2014, 2016, and 2018, but dropped to just below the long-term mean in 2022. The trends are dominated by age-0 pollock and juvenile sockeye salmon; in 2022 juvenile sockeye salmon were higher and age-0 pollock were lower.

  • *The biomass of motile epifauna measured during the standard EBS bottom trawl survey (Jun- Aug; 1982–2023) declined in 2023 from 2022 but remains above the long term mean. Collectively, brittle stars, sea stars, and other echinoderms account for more than 50% of the biomass in this guild, and current (2016–2023) mean biomass for all three of these functional groups are above their long term means. Brittle stars alone have accounted for more than 31% of motile epifauna biomass since 1997. They have trended downward since their peak biomass in 2016 but remain above their long-term mean. The current mean biomass index for king crabs, tanner crab, and snow crab are all below their long-term means. Trends in motile epifauna biomass indicate trends in benthic productivity, although individual species and/or taxa may reflect varying time scales of productivity.

  • *The biomass of benthic foragers measured during the standard EBS bottom trawl survey (Jun- Aug; 1982–2023) decreased from 2022 to 2023 and remain below the time series mean. The biomass of yellowfin sole decreased 32% from 2022 and remain below their long-term mean. Additionally, the biomass of flathead sole and Alaska plaice both declined. The biomass of northern rock sole increased 6.6% but remain below their long-term mean. Trends in benthic forager biomass are variable over the time series and indirectly indicate changes in availability of infauna (i.e., prey of these species).

  • *The biomass of pelagic foragers measured during the standard EBS bottom trawl survey (Jun- Aug; 1982–2023) decreased 34% from 2022 to 2023 and is below the long-term mean. The biomass of the pelagic forager guild was generally stable from 2016 to 2019, but dropped to their second lowest value over the time series (1982–2023) in 2021, and is now at its third lowest value in 2023. The trend in the pelagic forager guild is largely driven by walleye pollock that, on average, account for 68% of the biomass in this guild. In 2023, the index for pollock decreased 25% from 2022. Among species of secondary importance, Pacific herring have decreased 75% from a time series high in 2022, but remain above their long-term mean.

  • *The biomass of apex predators measured during the standard EBS bottom trawl survey (Jun- Aug; 1982–2023) in 2023 was nearly equal to their long-term mean. The trend in the apex predator guild is largely driven by Pacific cod, which had a modest increase from 2022, and arrowtooth flounder, which experienced a decrease from 2022. Trends in apex predator biomass reflect relative predation pressure on forage fish and crab.

  • *The multivariate seabird breeding index indicated that, on the whole, seabird reproductive timing and success at the Pribilof Islands was about average in 2023, although there were differences between islands and species that may reflect local-scale processes and/or diversity in foraging strategies. Seabirds had generally better reproductive success on St. George than St. Paul Island. Also, kittiwakes hatched earlier than average on both islands, while murres hatched about a week later than average. Reproductive success and/or early breeding are assumed to be mediated through food supply, therefore above-average values may indicate better than average recruitment of year classes that seabirds feed on (e.g., age-0 pollock), or better than average supply of forage fish that commercially fished species feed on (e.g., capelin eaten by both seabirds and Pacific cod).

  • Northern fur seal pup production at St. Paul Island in 2022 continued a declining trend since 1998 that may be partially attributed to low pup growth rates.

*indicates time series updated in 2023 Mean Trend  
*North Pacific Index
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*Sea Ice Extent
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*Cold Pool Extent
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*Proportion of Open Water Blooms
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*Large Copepod Abundance
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Euphausiid Biomass
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Pelagic 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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*Multivariate Seabird Breeding Index
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St Paul Northen Fur Seal Pups Born
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  2019-2023 Mean   2019-2023 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