Billions of crabs suddenly vanished, likely due to climate change, study says

Alaska's snow crab fishing industry came to a standstill in 2022 after an alarming disappearance of the animals, and now scientists are increasingly confident that man-made climate change is to blame for an ecological shift that killed them off.

In a new study from the National Oceanic and Atmospheric Administration on Wednesday, scientists said that rapid "borealization" – the shift from Arctic to sub-Arctic ecosystem conditions – is 98% likely to have been human-induced. The results were disastrous: roughly 10 billion crabs vanished between 2018 and 2021 and the industry went from a value of $227 million to nothing.

A heatwave in the Bering Sea's waters may have sped up the crabs' metabolisms, and with not enough food source for them to compensate, they starved to death, researchers said in a previous study.

“Even more concerning is that Arctic conditions conducive for snow crabs to retain their dominant role in the southeastern Bering Sea are expected to continue to decline in the future," Mike Litzow, lead author of the study and director of the Alaska Fisheries Science Center’s Kodiak Lab, said.

That could spell more bad news for the crabbing industry.

What happened to Alaska's crabs?

Between 2018 and 2021, there was an unexpected 92% decline in snow crab abundance, or about 10 billion crabs. The crabs had been plentiful in the years prior, puzzling scientists and crabbers alike.

A rapid warming of water temperatures and loss of sea ice from 2018 to 2019 made conditions less favorable to the crabs' survival. The increased temperatures themselves didn't seem to put too much stress on the crabs. But the impact on their metabolism caused their caloric demands to increase, and there wasn't enough available prey.

The scientists analyzed changes in ice cover, temperatures at the bottom of the ocean, algal blooms under the sea ice and the makeup of Arctic communities between 1972 and 2022. They determined that strong boreal conditions are about 200 times more likely now (at 1.0 to 1.5 degrees Celsius of warming) than before the industrial revolution.

“All of these factors are a result of climate change brought about by human activity since the start of the industrial revolution in the early 1900s," Litzow said.

Alaska's Department of Fish and Game said in 2022 that it was forced to make the tough decision to close the fishery for the season. After little sign of rebound, it was canceled again for the following year.

Earlier this year, Alaska Gov. Mike Dunleavy asked U.S. Secretary of Commerce Gina Raimondo to declare a fishery resource disaster for the 2023-24 Bering Sea snow crab fishery.

"The snow crab fishery is likely to remain closed over the next three to four years until the recovering population of smaller crab mature and reach legal size," Dunleavy said.

CLIMATE CHANGE:Alaska's snow crabs suddenly vanished. Will history repeat itself as waters warm?

What will climate change mean in the future?

There is some hope for the snow crabs in the short term, according to the study, which was published in the Nature journal on Wednesday. Conditions returned to cooler temperatures in 2022, closer to how they have been historically.

A plan to rebuild the snow crab population is in place with a target date of 2029. In the meantime, crabbers have had to adjust to fishing for different species, according to the NOAA.

The rapid changes seen in recent years sends a message that fishing industries need to be prepared for "complete loss of Arctic characteristics in traditional fishing grounds," the study authors said.

More warming is expected in the next decade to two decades, the study authors said. In fact, Arctic conditions are expected in only 8% of future years in the southeastern Bering Sea, the scientists said.

“It’s really important that fishermen, scientists, communities, and resource managers recognize that one of the most productive marine ecosystems in the world is changing – faster than anyone expected," Litzow said. "The time to act is now to think about how we are all going to adapt.”

Contributing: Trevor Hughes and Marina Pitofsky, USA TODAY