May 20, 2026 — Survey Progress and Bottom Temperatures

Every year, NOAA’s Alaska Fisheries Science Center conducts the eastern Bering Sea bottom trawl survey. We are mandated by the Magnuson-Stevens Act to collect distribution and abundance data for fish, crab, and other bottom-dwelling species in the Bering Sea. These data inform stock assessments and ecosystem status reports for the North Pacific Fisheries Management Council.

Temperature is one of many factors that influences species’ ranges and population sizes. For instance, we see many species moving farther north as ocean temperatures warm. To understand what’s going on in the Bering Sea, we record ocean bottom and surface temperatures at each sample station on the survey. These data will help us understand how variations in bottom temperature over time relate to the fish and crab we find—or don’t find—at the same station.

We will update this page with the most recent bottom temperatures recorded on most weekdays during the survey. For now, check out our completed 2025 bottom temperature map from the Bering Sea. This will be updated once the 2026 survey begins, and you’ll be able to see the updated temperature maps in near real-time. Note that in 2025 the survey included both the eastern and northern Bering Sea survey areas. In 2026, we will only survey the eastern Bering Sea area.

We have conducted the eastern Bering Sea survey annually since 1982 (except in 2020) making this the longest running, standardized time series of fish and invertebrate data in the region—43 years! Learn more about this survey, view temperature maps from previous years, and see examples of how these data are collected and used in this story from 2023.

All data collected on these surveys are and will be publicly accessible from:

• Fisheries One Stop Shop public data portal
• Distribution Mapping and Analysis Portal
• Alaska Fisheries Information Network

Documenting the Bering Sea Cold Pool

Survey data are crucial for understanding the extent of the cold pool, which is an important oceanographic feature of the Bering Sea.

Each spring, the previous winter’s sea ice melts to create dense, cold, ocean water, which sinks to the bottom of the Bering Sea. This creates the cold pool, which is defined as the total area where bottom temperatures are less than or equal to 2°C. The location of this cold pool changes from year to year and affects the movement and ranges of fish, crab, and other bottom-dwelling species. And it can act as a boundary separating Arctic species from subarctic species.

Commercially important fish like walleye pollock, Pacific cod, and snow crab are dependent on the location of the cold pool. Due to warming ocean temperatures in the Bering Sea, we track and closely monitor the location of the cold pool by collecting ocean bottom temperatures at each station.

Learn more about temperature anomalies, the cold pool, and how bottom temperatures in the Bering Sea have changed over time.

Read the full article at NOAA Fisheries

May 18, 2026 — Twenty years ago, Dr. George Rose with Memorial University of Newfoundland called capelin “a sea canary for marine ecosystem change.” A new study reinforces its role as a pillar of healthy marine ecosystems. It shows that heatwaves can dramatically affect capelin populations. Commercially important fish species like salmon and halibut rely on capelin as a food source—as do whales, seals, sea lions, and seabirds. And because they are not commercially harvested in the northeast Pacific Ocean, studying capelin in Alaska offers a unique opportunity to investigate population changes relative to environmental factors.

Between 2002 and 2022, Alaska Fisheries Science Center scientists observed capelin’s response to two marine heatwaves.They found declines in capelin abundance reduced energy available to predators to less than 1 percent of pre-heatwave values.

Capelin: an Indicator Species for Marine Ecosystems in Alaska

Lead author of the study Rob Suryan explains, “We consider capelin, along with herring, sand lance, and krill, to be the ‘big 4’ pelagic schooling forage species in Alaska. They are incredibly energy-rich—meaning they have a high lipid, or fat, content. And when they school, they form dense aggregations, which greatly increases foraging efficiency for predators. These two factors make them very valuable food for marine mammals, seabirds, and many commercial fish species.”

Abundant prey is critical for these predators. Decreased capelin populations, in particular, have been linked to declines in cod, birds, and seals and sea lions in both the North Atlantic and North Pacific Oceans.

In the North Atlantic Ocean, capelin are harvested for food, bait, and fishmeal by multiple countries. They are not commercially harvested in the northeast Pacific Ocean. Therefore, changes in capelin abundance and condition in the waters off Alaska primarily reflect natural changes that are independent of potential effects by commercial harvesting. This “canary” for ecosystem change in Alaska provides an important, unbiased indicator for understanding how environmental changes influence population fluctuations of capelin and other species throughout the ecosystem.

Read the full article at NOAA Fisheries