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In search of 10 billion missing snow crabs, scientists eye marine heat waves

The mass die-off shuttered the snow crab season during the winter of 2022-2023, threatening a key part of Alaska's economy.
The Bering Sea snow crab.
The Bering Sea snow crab.NOAA Fisheries

About 10 billion snow crabs disappeared from Bering Sea waters between 2018 and 2021, forcing fisheries to shutter in Alaska last winter and threatening the state’s economy. Now, scientists think they know what happened to them. 

A study published Thursday in the journal Science suggests that the crabs likely suffered a mass starvation event touched off by seasons of extreme ocean heat.  

The population crash — from its highest-recorded level in 2018 — shows how marine heat waves, which are made more likely by climate change, can scramble ecosystems and threaten human livelihoods that rely on ocean life. 

“Climate change is the next existential crisis for fisheries, and snow crab are a prime example for how quickly the outlook can change for a population,” the study’s authors wrote. 

Snow crabs require cold water to survive. In summer, they often flock to a cold pool that forms on the floor of the Bering Sea, between Alaska and Siberia. 

In 2018 and 2019, marine heat waves in the Bering Sea rendered the cold pool virtually nonexistent. 

Crabs’ metabolisms are temperature-dependent. The spike in water temperatures likely sent the crabs’ caloric needs soaring when their population was highly concentrated on the seafloor, leading to mass starvation. 

The researchers were able to rule out other issues that could have led to a population crash, including trawling, predation by other species and disease. It’s possible the crabs migrated elsewhere on the seafloor, but ships surveying other areas haven’t been able to find them. 

Snow crabs are big business in Alaska. A fleet of roughly 60 crab ships harvested snow crab in 2020, grossing roughly $132 million, according to a report from the Alaska Fisheries Information Network and the National Oceanic and Atmospheric Administration. 

The mass die-off shuttered the snow crab season during the winter of 2022-2023. 

The number of snow crabs remains too low to fish. Earlier this month, the Alaska Department of Fish and Game and the National Marine Fisheries Service announced the season would remain closed this winter, promising another difficult season for the crab fishing industry.