What caused snow crab to disappear from Alaskan waters?

The Alaska Department of Fish and Game (ADF&G) and the US National Marine Fisheries Service (NMFS) have completed annual surveys of fishery resources in the Bering Sea with a worrying conclusion. 

Snow Crabs Suddenly Disappear

The populations of snow crabs (mainly of the species Chionoecetes opilio ) are found in these waters of the North Pacific below the minimum legally established to guarantee the maintenance of resources and, consequently, they have decided to suspend the fishing season 2022-2023. 

It is the first time that the United States authorities have prohibited the fishing of this highly commercially valuable crab in the Bering Sea, although various scientific studies have warned in recent years that overfishing and environmental factors such as rising sea temperatures water populations were declining.

Earlier this month, Alaska announced that it had canceled its entire snow crab harvest for the year. The reason? Nearly 11 billion crabs have suddenly disappeared from the Bering Sea.

The news heralded a catastrophic population collapse for the animals, with nine out of ten going extinct between 2018 and 2021. It's a terrible development for those who make a living collecting crabs in a region of the world that is warming unusually fast due to its proximity to the North Pole. (Alaska officials also canceled the Bristol Bay red king crab harvest for the second year in a row.) This is not a small industry; Crab fishing in Alaska is worth more than $200 million a year. The sudden shutdown has left the state, well, in shock.

Snow crab population

In a statement, the Alaska Board of Fisheries and the North Pacific Fishery Management Council announced last week that the snow crab population in Alaska's Bering Sea fell below the regulatory threshold to open the fishery during the period 2022-2023.

The situation of this species of crab is alarming, from 11,700 million in 2018 to about 1,900 million in 2022, a reduction of around 84%, according to an estimate of an annual study of the bottom of the Bering Sea carried out by the National Office of Oceanic and Atmospheric Administration (NOAA).

In the early 1990s, Alaska's historic fisheries recorded more than 300 million pounds of snow crab. However, the landscape changed completely. For this year the figure does not exceed six million pounds, almost 90% less than 2021 levels, according to an investigation by The Seattle Times.

“The snow crab is by far the most abundant of all commercially caught Bering Sea crab species. So the impact of many billions of the population disappearing is noteworthy, and that includes all the females and calves," Daly told CNN.

Research into the disappearance of this species has shown that the main reason for this situation is climate change. Snow crabs are cold-water species and are found primarily in areas where water temperatures are below 2 degrees Celsius, according to Michael Litzow, director of NOAA Fisheries' Kodiak Laboratory.

“There have been a number of attribution studies that have looked at specific temperatures in the Bering Sea, or the Bering Sea ice sheet in 2018, and those attribution studies have concluded that those temperatures and the ice conditions under in the Bering Sea are a consequence of global warming,” Litzow said. As the oceans warm and sea ice disappears, the ocean around Alaska becomes inhospitable to the species.

It's not overfishing

More research is ongoing and the results should be published soon. Meanwhile, "everything points to climate change," Fedewa said.

"These are truly unprecedented and troubling times for Alaska's iconic crab fisheries and the hard-working fishermen and communities that depend on them," Jamie Goen, executive director of the Alaska Bering Sea Crabbers Association, said in a statement.

The sector was also affected by the cancellation of the Bristol Bay giant red crab fishery for the second consecutive year.

Fedewa also noted that overfishing is not a major factor in the collapse of the snow crab population.

Fishing only removes large adult males, he said, adding that "we've seen these declines in all sizes of snow crab, which really suggests there's some bottom-up environmental factor at play."

Alaskan snow crabs can reach 6 inches in carapace width, but females rarely exceed 3 inches, according to NOAA.

One piece of good news is that this year's study saw a significant increase in immature crabs compared to last year, but it will take four to five years before the males reach a fishable size.

After years of heat waves, temperatures have returned to normal, and "the hope is that leaving the crabs intact will allow them to reproduce, there will be no mortality and we can let the population try to recover," Fedewa said.

But that is a hope that depends on there not being more heat waves.

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