Gulf of Alaska 2019: It's All About the Food
Ecosystem Response to Warm Ocean Temperatures
During 2014-2016 the Gulf of Alaska ecosystem experienced a marine heatwave unlike any other seen in recent memory.
Unravelling the delayed effects of the 2014–2016 heatwave and another heatwave in 2019 on the marine ecosystem is challenging for scientists who have been monitoring the Gulf for decades.
From September 2018 through the end of 2019, the western Gulf of Alaska experienced another marine heatwave.
Animation by Southwest Fisheries Science Center, NOAA Fisheries (press play)
These unusually warm conditions had different effects on some species of plankton, fish, seabirds, and other animals in parts of the Gulf.
However, limits on food availability appeared to be a concern across many species.
In 2019, winter water temperatures were not as high as during the 2014-2016 marine heatwave, when declines of Pacific cod and seabirds (murres) were observed. But the summer temperatures were just as warm.
Common murres washed ashore in Alaska. Credit: Tamara Zeller, U.S. Fish and Wildlife Service
Die-off of Common Murres observed in Prince William Sound. Credit: Sarah Schoen, USGS, Alaska Science Center
A late phytoplankton bloom (rapid growth of the tiny algae that are the base of the marine food chain) occurred in the spring of 2019.
Microscopic veiw of diatom cells connected by organic threads to form a chain (thalassiosira)
Scientists recorded overall moderate to low abundances of phytoplankton in the Gulf of Alaska. These ocean plants are food for microscopic marine animals called zooplankton, as well as larval fish.
Background image shows phytoplankton bloom in the Gulf of Alaska. NASA Earth Observatory 2014
Scientists also observed lots of jellyfish in the water. Jellyfish are zooplankton predators.
Copepod with eggs. Credit: Matt Wilson, AFSC, NOAA Fisheries
Researchers sort jellyfish during ecosystem survey in Gulf of Alaska. Future studies will include looking at jellyfish diet and competition with fish for prey. Photo: NOAA Fisheries.
Zooplankton abundances appeared low to moderate overall, but were variable depending on the area surveyed.
Background Images: Matt Wilson
The story for seabirds this year was also mixed. Anecdotal evidence from Middleton Island suggests that some seabirds were bringing in more diverse prey than usual and traveling longer distances to find food.
On the Barren Islands at the mouth of Cook Inlet, scientists observed low numbers of fork-tailed storm petrel chicks, suggesting limited food availability may have been a factor.
On the Semidi Islands seabirds seemed to do better.
Many species of seabirds nest and rear their chicks on these remote islands.
Don Henise–Creative Commons
There were more Parakeet auklet fledglings per egg laid compared to average.
NOAA Photostream Flickr
Murres also seemed to have a more successful breeding year, suggesting that they were able to find the food they needed in 2019. However, the numbers of birds on breeding cliffs at the Semidi Islands was still only a little more than half the number that was counted, on average, in years before the 2014–2016 heatwave. Murres may defer breeding in some years due to poor feeding conditions. The continued low numbers at colonies may indicate population-level impacts of the 2015/2016 murre die-off, which included almost 1 million murres.
Black-legged kittiwake. Credit: Richard Hibpshman, Alaska Fisheries Science Center
Western GOA Black-legged Kittiwake Reproductive Success Alaska Marine Ecosystem Status Reports
In 2019, black-legged kittiwakes appeared successful in finding food to feed themselves while nesting, but may not have been able to find sufficient prey to feed their chicks when they hatched. Juvenile pollock and other small forage fish are important prey items for kittiwakes.
NOAA Fisheries surveys showed that juvenile fish abundance was down in the spring and fall, in particular for pollock in their first year of life.
Larval fish catch from Gulf of Alaska survey
Age 0 pollock
Juvenile sablefish
In NOAA Fisheries bottom trawl surveys, most adult groundfish, such as pollock and arrowtooth flounder, weighed less than average per length. However, there was some regional variability.
The exception was for Pacific cod, which were heavier than average per length. Pacific cod abundance is currently at an extremely low level. Fewer cod may have resulted in less competition for prey. This, in combination with rapid growth rates, may have enabled cod to build up their weight and grow unlike other fish species.
Slightly more humpback whales were observed during September 2019 in Prince William Sound than had been observed in 2017 and 2018.
Amy Kennedy
Fewer humpback whale calves and juveniles were seen in Glacier Bay in 2019. Mothers appeared to be thinner than normal, suggesting that they may have had trouble finding food or that there were lingering effects from the previous marine heatwave in 2014 to 2016.
Humpback whale calls
NOAA scientists continue to study the Gulf of Alaska marine ecosystem with our partners to support sustainable fisheries and healthy marine ecosystems.
Want to read more?
Check out our Ecosystem Status Brief and the 2019 full Ecosystem Status Report
Download the PDF : Gulf of Alaska Ecosystem Status Report: In Brief
Reference: Zador, S., et al., 2019. Ecosystem Status Report 2019: Gulf of Alaska, North Pacific Fishery Management Council, 605 West 4th, Suite 306, Anchorage, Alaska 99501
Contact: stephani.zador@noaa.gov
206-526-4693
