Bering Science

Harmful Algal Blooms

In the Bering Sea, the dinoflagellate Alexandrium catenella is the most common harmful algal bloom (HAB) species. HABs are dangerous because Alexandrium produces saxitoxin, which can cause paralytic shellfish poisoning (PSP) in animals and humans. The toxin also moves through the food web and affects wildlife at all levels, including those that do not consume shellfish.

How do HABs reach humans?

HAB toxins have been found throughout the Bering Sea food web. Saxitoxins produced by Alexandrium are ingested by zooplankton (like copepods) and filter feeders (like mussels, clams and forage fish), then move to the fish, birds and marine mammals that eat them. Humans can be exposed to the toxins when they eat these animals, especially shellfish. Researchers are still learning how much HAB toxins impact the behavior and survival of different animals.

HABs in the Northern Bering Sea

Scientists are concerned that warming conditions could lead to more HABs in the Bering Sea. In summer 2022, a large bloom of Alexandrium moved west past St. Lawrence Island through the Bering Strait. Water samples showed 100,000 Alexandrium cells per liter of water (1,000 cells are considered dangerous). Advisories were issued to communities during the event, which lasted six weeks. No human illnesses were reported.

How HABs move through the food web

Toxins in marine life

• Marine mammals HAB toxins have been found in all Alaska marine mammal species. No confirmed die-off events have been reported in the Bering Sea. Doses of saxitoxin in Bering Sea walruses were recently reported in the range known to impact the health of other mammals. This suggests that walruses may already be vulnerable to poisoning events, especially during warmer years.
• Clams Of all the Bering Sea animals tested, clams had the highest level of toxins. Higher levels occur in warmer waters. Compared to 2019 (the warmest year on record in the Bering Sea), clams in 2022 had low to moderate toxin concentrations.
• Seabirds Seabirds feed on small forage fish and marine invertebrates that accumulate HAB toxins. In recent years, scientists detected saxitoxin in multiple Bering Sea seabird species. The digestive tracts, livers and kidneys contain the most toxins, and muscle the least. Ongoing research on captive birds aims to better understand the effects of saxitoxin on seabirds.

Community monitoring

The Bering Sea’s remote and extensive coastline makes it challenging to study and track HABs. Community monitoring helps alert locals of potential HABs and provides essential data to scientists.

In the Aleutian Islands, the Qawalangin Tribe of Unalaska collects water samples to look for phytoplankton containing HAB toxins. Their data are reported to a national monitoring network. Shellfish samples are sent to Anchorage for toxin testing and the results are posted on the Tribe’s website. Several other communities in the Bering Sea are developing similar programs.

Storms like Merbok can wash clams ashore from deep water into areas where they are not usually found, making them available to subsistence harvesters. Shellfish collected after these storms are potentially dangerous, so caution should be exercised. The Alaska Harmful Algal Bloom network can fund shipping and testing of any samples.

Weekly toxin sampling in mussels in 2022. Sampling was done near Unalaska to monitor for PSP in blue mussels. Red bars indicate toxin levels dangerous to human health. Source: Qawalangin Tribe of Unalaska

For more information, visit https://ahab.aoos.org/.

Thanks to HABs research contributors

• Don Anderson, Woods Hole Oceanographic Institute (WHOI), danderson@whoi.edu
• Evie Fachon, WHOI, efachon@whoi.edu
• Thomas Farrugia, AOOS, farrugia@aoos.org
• Kathi Lefebvre, NOAA Fisheries, kathi.lefebvre@noaa.gov
• Shayla Shaishnikoff, Qawalangin Tribe, shayla@qawalangin.com
• Caroline Van Hemert, U.S. Geological Survey (USGS), cvanhemert@usgs.gov

Seabirds

Seabird die-offs and disease are recent hot topics in Alaska. In the Bering Sea, 2022 marked the sixth year of greater than normal seabird mortality, though the die-offs last summer were not as severe as in the past. There has also been recent interest in avian influenza across the United States. Fortunately, few seabirds in the Bering Sea were reported with the disease in 2022.

Seabird status on the Pribilof Islands

Apart from thick-billed murres, cliff-nesting seabirds had a great year on St. Paul and St. George islands in 2022. Kittiwakes did particularly well, with counts that were higher than in recent years.

In 2015–2016, a heatwave in the Gulf of Alaska killed many seabirds that nest in the Pribilofs. About 75% of common murres from some breeding colonies died during that time. The loss of murres was followed by several years of low breeding success, resulting in egg scarcity. In 2022, murres in Pribilof colonies finally seemed to return to normal breeding activity. Thick-billed murres were the exception—many lost their eggs right after laying.

Seabird die-offs

There were fewer reports of die-offs in 2022, but the number of carcasses found on beaches remains higher than expected. Prior to 2015, seabird die-offs were infrequent in Alaska. They usually took place in winter, and were related to disease or large-scale climate events like El Niño. Since 2017, hundreds to thousands of Bering Sea seabirds have died each summer and fall. The die-offs from 2017 to 2019 corresponded with unusually warm ocean temperatures. Related ecosystem changes that led to starvation likely caused the die-offs. For instance, warmer temperature and less sea ice may have impacted the zooplankton and forage fish that seabirds eat.

Circle sizes indicate totals of seabird carcasses reported each month. Locations with no reported carcasses may result from remoteness and/or lack of visitation or reporting capacity, rather than a lack of carcasses. Data compilation and map were provided by the Coastal Observation and Seabird Survey Team (COASST; University of Washington, Seattle WA), and uses data collected by Tribal partners, community members, Alaska Sea Grant, National Park Service, U.S. Fish and Wildlife Service and COASST participants.

Avian influenza

In 2022, a highly pathogenic avian influenza (HPAI) outbreak impacted birds across the U.S. and Canada. In the Bering Sea, fewer than 20 seabirds were confirmed to be affected. The positive cases were in gulls and jaegers, birds that may scavenge on carcasses of infected birds and mammals.

Seabirds nesting in dense colonies (like murres and kittiwakes) appeared to be unaffected, although limited seabird carcasses were collected and tested in the Bering Sea region in 2022. There was only one recent human case of HPAI in North America, and it was associated with exposure to infected poultry. The affected person reported mild symptoms and fully recovered.

Some birds infected with HPAI appear healthy, and others become sick and die. Common signs of disease among affected birds include a lack of coordination, stumbling, inability to stand upright, inability to fly, swimming in circles, a twisted neck and paralysis.

If you observe birds with these signs, please call the U.S. Fish and Wildlife Service Alaska Sick and Dead Bird Hotline—1-866-527-3358

• Recent confirmed detections of HPAI in wild birds—visit the U.S. Department of Agriculture at https://tinyurl.com/2p8r3ak8
• HPAI and human health—visit the Centers for Disease Control at https://tinyurl.com/35dsp8kpHunters: Learn how to limit your exposure to avian influenza at https://tinyurl.com/ysxy3mfe
• Hunters: Learn how to limit your exposure to avian influenza at https://tinyurl.com/ysxy3mfe

Thanks to seabird research contributors

• Robb Kaler, U.S. Fish and Wildlife Alaska Science Center, robert_kaler@fws.gov
• Jackie Lindsey, Coastal Observation and Seabird Survey Team, coasst@uw.edu
• Andrew Ramey, USGS Alaska Science Center, aramey@usgs.gov
• Heather Renner, Alaska Maritime National Wildlife Refuge, heather_renner@fws.gov

Weather & Climate

The big news of 2022 was, in a word, Merbok. In September, ex-Typhoon Merbok hammered 1,300 miles of Alaska coastline, with winds and storm surges that impacted communities and coastlines from Bristol Bay to beyond the Bering Strait. Because Merbok hit in early autumn, no sea ice existed to protect the coast.

Merbok: a “perfect storm”

Merbok reached its size and impacted Alaska in the way it did because of how specific atmospheric phenomena lined up.

• A typhoon in the far western Pacific Ocean formed where it is normally too cold to support a typhoon.
• Large scale winds at upper levels in the atmosphere steered the typhoon toward Alaska.
• A piece of the jetstream broke away from its normal wavy pattern, sending an additional “push” of extremely strong winds toward the region that helped strengthen the storm.
• The storm intensified further because of a strong difference in air temperature between the western and eastern Bering Sea.

If only one or two of these factors had occurred, Alaska would have experienced a more typical early autumn storm with heavy rainfall. It was the merging of all these pieces that gave Merbok its power. Though scientists expect storms like Merbok to become more common in the future due to climate change, Merbok-like storms will still be rare since at least three of the four puzzle pieces need to occur simultaneously. This is just one way that powerful storms can come to impact the Bering Sea region.

Alaska’s most well-documented storm

Organizations collecting data in the Bering Sea region collaborated to provide as much information as possible before, during and in the aftermath of Merbok. As the storm approached, a coordination team and communication pathways were quickly established so that data could be processed and provided to emergency responders and the public. As a result, Merbok was the most well-documented storm event in Alaska history.

Merbok data are available to the public and will help with ongoing damage assessment and community assistance. Data will also inform storm modeling, weather forecasting and long-term community planning.

Explore Merbok’s evolution, flood impacts, high water marks, and data collaboration efforts that were made to aid response and recovery: https://arcg.is/1umjSH0

Some of the damage inflicted by Merbok on western Alaska

Erosion impacts on community infrastructure

Erosion is an ongoing issue for many Bering Sea communities. The erosion caused by ex-Typhoon Merbok is still being analyzed. The Alaska Division of Geological & Geophysical Surveys (DGGS) has created erosion exposure assessments for the communities below, which may be useful for future infrastructure planning.

Information is shown using colors and graphics similar to those on this page. Download reports here: https://tinyurl.com/2wvckpr2

Projected erosion impacts for Newtok

Community reports produced by DGGS contain tables and maps such as these. These tables outline which, and how much, infrastructure may be impacted as the shoreline is projected to recede over the coming decades.

Graphic showing potential future erosion effects and creation of new shorelines over time. Graphics in DGGS reports use this color scheme.

Thanks to weather & climate research contributors

• Jacquelyn Overbeck, NOAA, jacquelyn.overbeck@noaa.gov
• Rick Thoman, UAF, rthoman@alaska.edu

Salmon

Yukon and Kuskokwim River Chinook and chum runs remained low in 2022, impacting subsistence harvests and food security. Agencies, many organizations and communities are working together to learn how changing environmental conditions—especially warmer temperatures—affect salmon. When possible, sampling efforts are coordinated to minimize how many fish are used for research.

Juvenile salmon surveys

NOAA Fisheries and ADFG monitor juvenile (first year at sea) salmon from Western Alaska in the Bering Sea each September. Chinook, chum and sockeye salmon typically spend two to four years at sea.

In 2022, abundance of both juvenile Chinook in the northern Bering Sea and juvenile Yukon River Fall Chum was below average. Juvenile sockeye abundance remained high in the southeastern Bering Sea.

Factors affecting juvenile chum salmon

Yukon Fall Chum spend their first summer in the Bering Sea, then migrate to the Gulf of Alaska for winter. Juvenile chum survival decreased during heat waves in the Bering Sea and Gulf of Alaska. Young chum caught during that time had more empty stomachs and less fat. They were eating jellyfish and other less nutritious prey at a time when the number of high-fat zooplankton in the Bering Sea was low. Researchers are trying to learn more about their early life history to learn how ocean water temperature and prey availability may affect chum runs.

Juvenile sockeye abundance in the eastern Bering Sea

Juvenile sockeye abundance in the eastern Bering Sea, millions. Credit: NOAA Fisheries

Juvenile chum per square kilometer, upper Yukon River

Credit: NOAA Fisheries

Juvenile Chinook abundance in the northern Bering Sea

Juvenile Chinook abundance in the northern Bering Sea, millions. Credit: NOAA Fisheries

Record Bristol Bay sockeye runs in 2022

Over 79 million sockeye salmon returned to Bristol Bay in 2022—the largest run on record. Average runs in the last 20 years have been about 44 million fish. This record run size provided more than enough fish for the spawning grounds, harvest by subsistence and sport fisheries, and a commercial harvest of 60 million sockeye salmon that exceeded the previous record by 16 million fish.

Why are sockeye doing relatively well? Juvenile sockeye use lakes—cold, deep water and more food (due to a shorter ice season) help grow healthy salmon.

Ongoing research: stressed Yukon Chinook salmon may produce fewer offspring

Warmer ocean temperatures, extremely warm river temperatures and lower river flows can affect how well salmon can acquire, store and use energy—and, ultimately, reproduce. Scientists and local people are working together to test these ideas and gain a better picture of Chinook salmon declines. This work involves sampling at sea and across the Yukon basin with team work of ADFG, USGS, the Yukon River Drainage Fisheries Association (YRDFA) and NOAA Fisheries. Other collaborators include Tribal councils in Emmonak, Alakanuk, St. Mary’s and Huslia, as well as Canadian partners.

Poor food quality, migration length and warmer water appear to reduce reproductive success: fish may die early and produce fewer eggs. If eggs lack key nutrients, their survival rates are poor. Source: Katie Howard (ADFG) and Vanessa von Biela (USGS)

Wildfire impacts on salmon?

Western Alaska had a record wildfire season in 2022. The East Fork Fire in the Andreafsky River watershed near St. Mary’s was the largest wildfire in the Yukon Delta region in recorded history. In the years following a wildfire, sunlight penetrates to ground level into burn scars, warming land and water. Warming effects are large—several degrees Fahrenheit—and last for over a decade. On the Andreafsky River, water temperatures were already high enough to cause heat stress in Chinook salmon before the wildfire, so further warming could reduce the survival of spawning adults or eggs in coming years.

Ichthyophonus infecting salmon

Ichthyophonus has infected many species of fish worldwide, including Yukon River Chinook salmon. The disease is caused by a parasite. Infected fish have white lesions on their flesh and hearts. Subsistence fishers reported increasing presence of Ichthyophonus in 2020 and in 2021, prompting a study to better understand how many fish could be dying from the disease prior to spawning. Preliminary results from fish sampled on the Yukon River show an increase in Ichthyophonus in 2022. The study will continue for two more years.

Local knowledge of Yukon River salmon

Projects that share western science and Indigenous knowledge will help us better understand how climate impacts Chinook and chum. In a new study, YRDFA will facilitate interviews with experienced fishers and processors in Emmonak and Alakanuk. They will be asked about their observations of Chinook and chum harvested at the mouth of the river. Their knowledge of the health, condition and run timing of the fish will help us better understand the historic and current health of Chinook and the effects of their marine diet.

YRDFA is also working with residents of St. Mary’s and Huslia to develop community capacity to help in understanding the decline in Yukon River salmon. This includes water temperature monitoring, coordinating local data collection for annual carcass surveys, and creating a rapid community response plan to assess salmon die-off during a heat event. This work will increase local hire and training on salmon related research.

Fisheries disaster declarations

ADFG is responding to fisheries disaster requests and developing spending plans for federal disaster relief funds. Disasters have been declared and funds announced for:

• 2019 Norton Sound red king crab ($1,433,137) 2019/2020 Eastern Bering Sea tanner crab ($12,935,199)
• 2020 Norton Sound, Yukon River, Kuskokwim River and Chignik salmon; and 2021 Yukon River salmon (part of $55,928,849 for statewide salmon disasters)
• Disasters have been approved for: 2020 and 2021 Norton Sound red king crab 2021 Kuskokwim River, Norton Sound and Chignik salmon 2021–2022 and 2022–2023 Bering Sea crab
• A request for the 2022 Yukon River salmon fishery is pending.

Find updated information at these websites:

• ADFG Federal Fisheries Disasters
• NOAA Fisheries Fisheries Disaster Determinations

Thanks to salmon section contributors

• Karla Bush, ADFG, karla.bush@alaska.gov
• Travis Elison, ADFG, travis.elison@alaska.gov
• Jayde Ferguson, ADFG, jayde.ferguson@alaska.gov
• Katie Howard, ADFG, kathrine.howard@alaska.gov
• Catherine Moncrieff, YRDFA, catherine@yukonsalmon.org
• Jim Murphy, NOAA Fisheries, jim.murphy@noaa.gov
• Erik Schoen, UAF, eschoen@alaska.edu
• Vanessa von Biela, USGS, vvonbiela@usgs.gov