NOAA says Bering Sea snow crab collapse is result of human-caused climate change

ANCHORAGE, Alaska (KTUU) - The snow crab population in the southeastern Bering Sea has been drastically reduced in recent years due to human-caused climate change, according to the National Oceanic and Atmospheric Administration (NOAA).

Scientists with NOAA say there’s been an ecological shift from Arctic to sub-Arctic conditions since the preindustrial era.

“Out in the Bering Sea, we only find snow crab in really cold conditions, like 2 or 3 degrees Celsius, just above freezing,” said Mike Litzow, the director of the Kodiak lab for NOAA Fisheries. “And those are areas that have sea ice in the winter.

“If you bring those snow crab into the lab, you can raise them up to 8 degrees C and they do fine so it’s not like a direct thermal tolerance problem. It’s something with the ecosystem change.”

Litzow says that the impacts of the snow crab collapse cannot be understated. He estimates the fishery was worth almost $230 million a few years ago.

He says that there has been a big focus on trying to understand what happened. The dire situation was highlighted in 2018-2019, when the snow crab population experienced a decline of roughly 90 %.

“That really low ice condition, those really warm temperatures in the Bering Sea in 2018 and 2019 are not consistent with natural climate variability,” Litzow explained, “that you can only get the Bering that warm, you can only see that little sea ice in the winter in the Bering with human-caused climate change.

“So we really see the fingerprints of [human] changes to the climate on this particular event.”

Litzow said the study empowers scientists to assess risk as the climate continues to warm.

“The take-home [message] is in the traditional grounds for the snow crab fishery — you know, where we normally fish them in the southeast Bering Sea — we should just really expect continued warming events like this to make things tougher and tougher for snow crab,” he said.

Litzow says scientists determined the crab decline is human-caused by taking a closer look at 2018 and 2019 conditions to see what led to low sea ice and sub-Arctic conditions.

“We took 23 different climate models — global climate models — from groups working around the world, and we looked at their pre-industrial runs,” explained Litzow. “So those modeling groups run their climate models with a pre-industrial atmosphere, and then they run the same model with the current concentration of greenhouse gasses in the atmosphere.

“Under pre-industrial conditions, you see those very warm low sea ice years as incredibly rare events, but in the sort of the warming category that we’re in now, you see those very warming conditions being 200 times more likely.”

While the snow crab population is decreasing due to warming seas, some species are doing quite well.

Litzow says Bristol Bay’s red salmon are running strong, while sablefish are doing well with warmer conditions in the Gulf of Alaska and the Bering Sea.

“And then with crabs in the Bering Sea, we’re really seeing tanner crab numbers take off on our survey and they’re very closely related to snow crab, but they’re the more southern, warm temperature species,” he said. “So it might be that longer term in the southeast Bering Sea, we do see a transition from snow crab to more tanner crab numbers.”

In the interim, there is hope for a snow crab rebound.

“And so after the collapse in snow crab, in 2022 we saw a small snow crab appearing on our survey and those numbers of small snow crab have continued to increase in 2023 and this summer in 2024,” Litzow said.

“So as long as it stays cold and as long as those snow crab have the conditions they need to grow into commercial size, we’re hopeful that in a few years, we might see a rebound and get people fishing again.”

Ultimately, Litzow said it’s time to prepare for warmer seas.

“I guess the message is that it’s coming sooner than we think,” he said.

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