A Few Surprises in Alaska’s Marine Environment in 2024

The Gulf of Alaska and Aleutian Island waters were on the warm side for a good part of the year. In fact, winter sea surface temperatures in 2023-2024 were among the 10 warmest years since 1900 in the Aleutians. The eastern Bering Sea appears to be in a period of transition as it continues to recover from record heatwave conditions (2014-2021).

This year's Ecosystem Status Reports provide a comprehensive look at 2024 conditions and trends over time (whether some indicators were increasing or decreasing) for key indicators. Scientists use these indicators to monitor Alaska marine ecosystem health.

"We look at numerous indicators that tell us about the ocean environment, the animals that live there, what they're eating, who is eating them and how healthy they all are. That includes everything from water temperature, pH, ocean currents, and weather patterns to abundance of plankton, fish, crabs, seabirds, marine mammals and other species," said Bridget Ferriss, author of the Gulf of Alaska Ecosystem Status Report.

Value of Ecosystem Data and Information for Resource Management

For close to three decades, fishery managers have relied on these reports to better understand how federally managed commercial fish and crab populations are being affected by changes in the marine environment.

Scientists who develop ecosystem status reports work closely with the scientists who produce fish and crab stock assessments to document how changes in the marine environment may affect individual stocks. Some key indicators they monitor include changes in abundance and body condition including energy density as a way to measure fish, crab and other species fitness or overall health.

For example, this year, for the eastern Bering Sea Report, scientist Elizabeth Siddon documented how ecosystem indicators for Pacific cod may be adversely affecting this species in the eastern Bering Sea. Specifically, prey availability over the southern shelf may be a factor affecting the decline in Pacific cod weights at various ages, which declined during 2022-2024. She also pointed out that the biomass of competitors of Pacific cod have been increasing. This includes arrowtooth flounder, which increased approximately 26 percent, and Alaska pollock, which increased approximately 74 percent, in the center's bottom trawl survey from 2023 to 2024.

This year also marked the first time that NOAA Fisheries was able to produce a report card on trends for the northern Bering Sea within the Bering Sea Ecosystem Status Report.

Scientists also collect a variety of data and information on other species, such as salmon, as indicators of ecosystem status.

Of note this year, commercial salmon landings were some of the lowest since 1985 in the Gulf of Alaska. Southeast Alaska juvenile pink salmon were smaller and had lower energy density.

In the Aleutians, pink salmon abundance was low, which is typical for an even year.

In the northern Bering Sea surface trawl survey, juvenile Chinook salmon abundance was at a record low while fall juvenile chum salmon abundance was at a record high. Juvenile pink, chum, and coho salmon body condition was about average while Chinook salmon condition was above average. Bristol Bay sockeye abundance has remained at above average levels since 2015. However, juvenile sockeye energy density was low.

Ecosystem Data Contributions: It Takes a Village

Ecosystem Status reports are developed each year with input from many sources.

"All of this is possible, because of the critical contributions we receive from numerous partners," said Ivonne Ortiz, author of the Aleutian Islands Ecosystem Status Report. "Federal, state, and academic researchers, fishermen, coastal community members, tribes, and a host of others contribute to these reports. We couldn't do it without their help and knowledge."

Also critical to the development of these annual ecosystem status reports is the research conducted by scientists who work in the lab and on research boats to conduct process studies. These studies explore fish ages, body condition, genetics, prey relationships, food web and caloric content of species. Equally important are broadscale data on sea ice abundance, harmful algal blooms, species' genetics, and more.

Ecosystem Status Report authors noted that another developing area of research is environmental DNA . NOAA Fisheries scientists are exploring the use of this tool to learn more about Arctic cod distributions, northern fur seal and Steller sea lion diets, and ice seals. At this point, using eDNA to directly support fisheries management is still in the early stages. It shows promise because it is an easy and efficient way to collect relative abundance for individual and multi-species and fill spatial and temporal survey gaps. However, we still need scientists to collect needed biological data such as size and age of fish to inform stock assessments.

In 2024, data from the Ecosystem Status Reports provided broad, contextual ecosystem information for 45 stock assessments and specifically informed 23 stock-level risk assessments.

2024 Highlights Across Alaska

Looking across the three ecosystems this year, there are several notable indicators amidst continued variability in many marine conditions.

Ocean Temperatures

Ocean temperatures in the Bering Sea have cooled to average thermal conditions. Ocean temperatures in the Gulf of Alaska were warm in the winter and spring. In the Aleutians, temperatures cooled but remained warmer than average in winter and cooled to average for the rest of the year. The exception was in the western Aleutians, where they have remained warm since mid-late summer. Bottom temperatures were near average across the chain.

Groundfish

Pacific ocean perch continue to be the dominant groundfish in the Aleutian Islands, replacing pollock and Atka mackerel in the ecosystem. The Gulf of Alaska groundfish are now dominated by zooplankton-eating groundfish (Pacific ocean perch, walleye pollock) over fish and invertebrate-eating groundfish (arrowtooth flounder, Pacific cod, Pacific halibut).

Indicators of Ecosystem Health and Potential Threats

Harmful algal blooms are becoming more prevalent in the northern Bering Sea. Harmful algal blooms in the Gulf of Alaska slightly decreased in frequency, intensity, or duration, but areas continue to have shellfish testing above the regulatory limit.

Paralytic shellfish toxins in sampled blue mussels from Unalaska in the Aleutian Islands were seven times above the regulatory limit (compared to 47 times in 2023).

Gulf of Alaska

• Long-term trends in the Gulf of Alaska include warming ocean temperatures, changes in salinity, and a shift in the groundfish community to more zooplankton-eating fish.
• Moderate El Niño conditions occurred during the winter of 2024, including warm winter and spring surface temperatures and increased shelf circulation. Few ecological responses to the warm event were observed.
• Feeding conditions for groundfish improved from 2023 to generally above average. Biomass of zooplankton increased, including larger, nutritious species (large copepods, euphausiids). Forage fish (herring, capelin, others) abundance continued to be above average across the Gulf of Alaska.
• Commercial salmon landings were some of the lowest since 1985, driven by unexpected low returns of pink salmon in Prince William Sound. Low returns were probably due to poor juvenile marine survival in 2023 and potential competition in the ocean gyre (2023-2024).

Aleutian Islands

• Winter sea surface temperatures in 2023-2024 were among the ten warmest since 1900.
• Strong winds and storminess from winter through spring cooled temperatures to average during late spring and summer and resulted in a deeper mixed layer. This potentially impacted the vertical distribution and availability of prey throughout the water column.
• The ecosystem showed signs of a gradient of poor productivity in the west to high productivity in the east, largely based on counts of Steller sea lions and seabird reproductive success.
• Eastern Kamchatka pink salmon abundance was low. This is typical in even-numbered years. However, this "low" abundance of roughly 60,000 tons is similar to what was considered high abundance in the 1970s and 1980s. In recent odd-numbered years, high pink salmon abundance is similar to Pacific cod's highest biomass of approximately 250,000 tons.
• Groundfish condition remained poor across the ecosystem despite the relaxation of the multi-year warm conditions and a low abundance year in the biennial Kamchatka pink salmon cycle. The condition of Pacific cod, northern rockfish, and Pacific ocean perch have been below the long-term average since 2012. The decline in fish condition may be indicative of several interacting factors including poor prey quality, low availability of prey, competition, and increased energetic cost of living.

Eastern Bering Sea

• The Bering Sea has cooled to average thermal conditions 2022-2024 after record warm conditions during an unprecedented warm stanza (2014-2021).
• Under average thermal conditions-not warm or cold-the Bering Sea ecosystem is in a transitional state with some species abundance increasing and others decreasing.
• Persistent storms throughout the summer mixed the upper water column deeper, which brought cooler water into the surface layer. Storms continued into fall mixing nutrients and led to an early fall phytoplankton bloom.
• Pelagic prey was dominated by small copepods over the southern middle domain with large oceanic copepods available over the outer shelf.
• Benthic epifauna was dominated by echinoderms (e.g., brittle stars, sea stars) while crab biomass remains low.
• The northern Bering Sea has seen a step-change increase in sea ice thickness since 2021, which may indicate increased ice algae productivity in the region.
• The northern Bering Sea had some signs of improved zooplankton abundances in 2023 and 2024.

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