The western Gulf of Alaska remained in heatwave conditions for most of 2019. Summer sea surface temperatures were similar to the warmest temperatures during the 2014-2016 marine heatwave. The
PDO declined to neutral, reflecting warm conditions across the NE Pacific (with no temperature contrast in the central Pacific that describes the positive or negative PDO pattern).
Mesozooplankton biomass measured by the continuous plankton recorder declined in 2018 ending a stretch of positive abundance anomalies seen from 2014-2017.
Copepod community size was larger in 2017 and 2018 than it had been during the 2014-2016 heatwave, indicating that there were more large species available. However, the lower biomass in 2018
indicates a potential decline in foraging conditions for planktivorous predators relative to that in 2017.
Bottom trawl survey biomass of motile epifauna increased from 2017 to 2019 (10%) and is above the long term mean. The biomass of this guild is dominated by octopuses, hermit crabs,
and brittle stars. Octopuses increased to their highest value over the time series, while both hermit crabs and brittle stars decreased to well below their long-term means.
Trends in capelin as sampled by rhinocerous auklets at Middleton Island have indicated that capelin were abundant from 2008 to 2013, but continue to be minimal in seabird chick diets in recent
years. Their apparent decline coincided with the period of warm water temperatures in the Gulf of Alaska.
Fish apex predator biomass during 2019 bottom trawl survey increased from 2017 to 2019 (13%) but remains well below the long-term mean. The trend is driven primarily by increases in Pacific cod and arrowtooth flounder which are both at their second lowest abundance in the survey time series, and increases in sablefish, which is above their long-term mean and at its third highest abundance in the survey time series.
Black-legged kittiwakes had above average reproductive failure in 2019 at the Semedi Islands. The failure occurred during the chick-rearing period, potentially indicating a rapid decline in prey
availability for these surface-feeding seabirds. In contrast, diving, fish-eating seabirds in the western GOA had strong reproductive success in 2019.
Although Steller sea lion non-pups were counted in 2019, the data were not available in time for this report. Modelled estimates of western Gulf of Alaska Steller sea lion non-pup counts were
approaching the long-term mean in 2017, suggesting conditions had been favorable for sea lions in this area. However, estimates show a decline in the number of pups from 2015 to 2017 and declines
in the number of non-pups in the Cook Inlet, Kodiak, and Semidi area.
Human populations in fishing communities in the western Gulf of Alaska have increased since 1990 largely in urban areas.
Figure 4: Western Aleutian Islands ecoregion indicators. * indicates time series updated in 2019.
Eastern Gulf of Alaska 2019 Report Card
There was a weak-moderate El Niño last winter. Near-neutral El Niño expected for winter 2019-2020. .
Total zooplankton density in Icy Strait in 2019 was slightly below average and and represented a slight decline from 2017 and 2018. This suggests about average foraging conditions for planktivorous fish, seabirds, and mammals and an improvement relative to the below-average densities during 2013-2016.
However, the overall copepod community size remained low due to below-average abundance of large copepods while small copepods were nearly average. This suggests below-average quality
zooplankton prey, confirmed by low lipid content in all measured zooplankton taxamonic groups.
Bottom trawl survey biomass of motile epifauna remained well above the long-term mean in 2019 (2nd highest over the time series). Brittle stars are the largest contributor to biomass in this
guild and increased 9% from 2017. Other large increases in biomass from 2017 to 2019 were observed with hermit crabs (526%) and eelpouts (276%).
A decrease in estimated total mature herring biomass in southeastern Alaska has been observed since the peak in 2011. Modeling indicates that the declines in biomass may be related to lower survival.
Bottom-trawl survey fish apex predator biomass increased slightly (2%) from 2017 to 2019 but remains below the long-term mean. Arrowtooth flounder are the dominant component of
the biomass in this guild and increased 7% from 2017. Other groups contributing to the increase in guild biomass are sablefish, big skate, and Pacific cod.
Growth rates of piscivorous rhinoceros auklet chicks continue to be anomalously low, similar to the 2015-2016 heatwave years, suggesting the adults were unable to find sufficent
prey to support optimal chick growth. However, burrow residency indices (a proxy for reproductive success), suggests that there were some successful nesting attempts.
Although Steller sea lion non-pups were counted in 2019, the data were not available in time for this report. Modelled estimates of eastern Gulf of Alaska Steller sea lion non-pups counts were above
the long term mean through 2017. However, counts suggest that non-pup counts declined 12% in 2017 relative to 2015. This unusual decline in a long-increasing stock may indicate adverse responses
to the marine heatwave of recent years.
Human populations in fishing communities in the eastern Gulf of Alaska have remained stable since 2000, with minimal decadal changes. There were no significant population changes within large
communities between 2010 and 2018.