Snow crabs sampled during the 2024 eastern Bering Sea bottom trawl survey. Credit: NOAA Fisheries / Erin Fedewa

Bering Sea Snow Crab Collapse Linked to Energetic Crisis During Marine Heatwave

UNITED STATES
Thursday, December 11, 2025, 08:30 (GMT + 9)

New Metric Offers Hope for Early Detection and Future Fisheries Management

A new study has provided critical insights into one of the largest mass mortality events in recent marine history: the abrupt collapse of the snow crab population in the eastern Bering Sea during 2018–2019. The findings point to severe energetic limitations—a state of low energy reserves—triggered by the combination of a marine heatwave and high population density.

The research team, led by NOAA Alaska Fisheries Science Center fishery biologist Erin Fedewa (Pictured), set out to identify the factors driving the increased mortality, population collapse, and recovery potential of the Bering Sea snow crab.

Warming and High Population Density Created a "Perfect Storm"

The study is the first of its kind for Bering Sea crab stocks to directly measure snow crab energy reserves during and after the collapse.

• Key Finding: Decreases in crab abundance were associated with dramatic declines in the energetic condition of juveniles.

• The Cause: Researchers concluded that warmer conditions brought on by the 2018–2019 marine heatwave combined with high population density—likely creating too much competition for food—led to the collapse.

Fedewa noted the concern: "It’s always a concern when you see impacts to juveniles. They represent the future of the population and the fishery."

NOAA scientist Erin Fedewa collects snow crab hepatopancreas samples during the 2023 eastern Bering Sea bottom trawl survey to monitor energetic reserves of juvenile snow crab. Credit: NOAA Fisheries / Emily Markowitz

Historically, snow crab have been associated with the cold pool in the Bering Sea (cold bottom waters less than 2 degrees C). However, study co-author Mike Litzow (pictured), director of the Shellfish Assessment Program in Kodiak, stated, "Our results underscore the consequences associated with elevated temperatures and high population density and point towards the critical importance of cold-water habitat for snow crab recovery in the eastern Bering Sea." The authors were surprised to find that much colder temperatures, specifically below 0 degrees C, appear necessary for promoting elevated energy reserves and high survival.

A New, Rapid Energetic Condition Metric for Fisheries Management

To help track stock health, the research team successfully validated a new, practical metric for monitoring snow crab energetic condition.

Scientists collect additional data on individual snow crab sampled for hepatopancreas, including weight, size, and maturity status. Credit: NOAA Fisheries / Emily Markowitz

Traditional techniques for monitoring energy reserves in crustaceans often require complex, time-intensive, and costly analysis. To address this, the team focused on the hepatopancreas, the primary energy storage organ in crustaceans like crabs. Since 2019, they have been collecting and weighing hepatopancreas samples from juvenile snow crabs during annual Bering Sea trawl surveys.

NOAA scientist and co-author Louise Copeman (Pictured) explained the breakthrough: "We demonstrated a strong positive relationship between the easy-to-measure hepatopancreas percent dry weight and total fatty acid concentration, which is more complex to measure."

This new, efficient metric offers an early-detection system to track snow crab energetic limitations and mortality risk. Fedewa added that these condition estimates are already communicated to stakeholders and fishery managers in the Snow Crab Ecosystem and Socioeconomic Profile, providing a near-real time measure to inform management decisions.

Energetic Rebound Suggests Snow Crab Population Recovery

In a promising sign, the study observed that the energetic condition in the eastern Bering Sea snow crab population rebounded quickly following the marine heatwave.

Scientists collect snow crab hepatopancreas samples to monitor energetic reserves of juvenile snow crab during the 2023 eastern Bering Sea bottom trawl survey. Credit: NOAA Fisheries / Emily Markowitz

This increase in energy reserves coincided with strong recruitment and increasing population abundance from 2021 to 2024. Fedewa expressed cautious optimism: "Support for initial population recovery is very encouraging, but strong recruitment in the near-future is critically dependent on conditions that promote high energetic reserves and survival of juvenile snow crab. The population is still vulnerable to another marine heatwave."

The authors, whose research was funded by the North Pacific Research Board, emphasize the importance of continued energetic-based sampling in the Bering Sea to better prepare for future environmental surprises. Copeman noted that future work includes using results from food deprivation experiments conducted at the science center’s Newport Lab to determine critical energetic thresholds.

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