Eastern Bering Sea 2019 Report Card (pdf)
- The North Pacific Index (NPI) was mostly positive during 2018 into early 2019, resulting in relatively high sea level pressures in the region of the Aleutian low. The NPI turned negative in the spring of 2019; negative NPI commonly accompanies El Niño conditions. Plotted here is the Nov-Mar average showing near-neutral conditions for 2019.
- The mean sea ice extent across the Bering Sea (1 August-31 July; western and eastern) has exhibited no long term trend, though four of the past five seasons have a mean ice extent lower than
any season prior to 2014-2015. Variability in sea ice extent has increased over the time series, with above-average ice in 2012-2013 followed by a steady decline to below-average ice in recent years. The 2018-2019 daily mean sea ice extent was less than half of the 1981-2010 average and is the second lowest of record (only 2017-2018 was lower). Seasonal sea ice extent has implications, for example, to the cold pool, spring bloom strength and timing, and bottom-up productivity.
- The eastern Bering Sea experienced a second winter of
low sea ice conditions , which resulted in a reduced cold pool over the northern shelf.
- The acoustic survey that provides estimates of euphausiid density occurs biennially in even years. Look for an update in 2020.
- The biomass of motile epifauna sampled during the summer bottom trawl survey remains above the long-term mean, but is down 10% from 2018. The decrease is due to brittle stars (-3%) and urchins, sand dollars,and cucumbers (-28%), however, both groups remain well above their long-term means. Opilio crab decreased 43% and Tanner crab decreased 38% from 2018. Trends in motile epifauna biomass indicate benthic productivity, although individual species and/or taxa may reflect varying time scales of productivity.
- The biomass of benthic foragers remained low in 2019 (4th lowest in the time series) and is largely due to both Yellowfin sole and Northern rock sole being below their long-term means. Northern rock sole have declined steadily since 2010 and are down 10% from 2018. Trends in benthic forager biomass are variable over the time series and indicate availability of infauna (i.e., prey of these species).
- The biomass of pelagic foragers is up 13% from 2018 but remains below the long-term mean . Pollock increased 74% and Jellyfish 164%. Pacific herring decreased 24% but remain above their long-term mean. Pacificsandlance have declinedeach yearsince 2015 and aredown 43%from 2018. 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.
- The biomass of fish apex predators is up 2% from 2018 and remains approximately equal to the long term mean. Pacific cod have decreased each year since 2015 and are well below their long-term mean (down 2% from 2018). Losses in Pacific cod since 2017 have been partially offset by increases in Arrowtooth flounder which are up 13% from 2018. Trends in apex predator biomass reflect relative predation pressure on zooplankton and juvenile fishes within the ecosystem.
- The multivariate seabird breeding index increased above the long term mean, indicating that overall, seabirds bred earlier and had better reproductive success in 2019 in relation to the past few years. However, murre numbers remain low, and least auklets on St. Paul Island experienced their fourth year of poor reproduction, indicating incomplete recovery from the previous three years of poor conditions. Reproductive success and/or early breeding are assumed to be mediated through food supply, therefore above-average values 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 2018 was 6.1% less than the 2016 estimate. Pup production has been declining at St. Paul Island at an annual rate of 4.0% since 1998. Northern fur seal population decline at St. Paul Island may be attributed to low pup growth rates due, in part, to extended foraging trips required for nursing females to provision pups (see p. 30).
- 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. Fishing gear can affect habitat used by a fish species for the processes of spawning, breeding, feeding, or growth to letter-spacing: maturity.