The sudden and dramatic disappearance of billions of snow crabs around Alaska is a disturbing indication of the impacts of climate change on marine ecosystems.
A study from the National Oceanic and Atmospheric Administration (NOAA) study has linked the disappearance of the snow crabs to marine heat waves in the eastern Bering Sea. The experts say that warmer ocean temperatures likely caused the crabs to starve to death.
“The snow crab is an iconic species in the Bering Sea that supports an economically important fishery and undergoes extensive monitoring and management. Since 2018, more than 10 billion snow crabs have disappeared from the eastern Bering Sea, and the population collapsed to historical lows in 2021,” wrote the study authors.
“We link this collapse to a marine heatwave in the eastern Bering Sea during 2018 and 2019. Calculated caloric requirements, reduced spatial distribution, and observed body conditions suggest that starvation played a role in the collapse.”
Due to the decline, the Alaska Department of Fish and Game has canceled the snow crab harvest season for two consecutive years.
Study lead author and NOAA fishery biologist Cody Szuwalski told CNN: “When I received the 2021 data from the survey for the first time, my mind was just blown.”
“Everybody was just kind of hoping and praying that that was an error in the survey and that next year you would see more crabs. And then in 2022, it was more of a resignation that this is going to be a long road.”
While overfishing was initially suspected as the culprit, it doesn’t explain the dramatic collapse. The researchers considered two primary explanations for the crabs’ disappearance: they either moved to another location, or they died.
After analyzing various areas and factors, they concluded that a mass mortality event was the primary reason for the loss of the crabs.
“Our results do not support a strong connection between variability in snow crab mortality and indices of trawling, predation, cannibalism, or disease,” wrote the researchers.
“All of these forces must contribute to underlying mortality to some degree, but several observations corroborate the idea that temperature and population density were the key variables in the recent collapse.”
Warmer waters affect the metabolism of snow crabs, increasing their caloric needs. With disrupted food webs due to the heat, the crabs couldn’t find enough food to meet their increased energy demands.
The absence of a temperature barrier allowed Pacific cod to enter the crabs’ habitat during the heat wave, further decimating the crab population.
The Arctic region, especially the Bering Sea, has experienced rapid warming and a dramatic loss of sea ice. This accelerates global warming and has direct implications for marine life.
“This was a huge heat wave effect,” study co-author Kerim Aydin told CNN. “When the heat wave came through, it just created a huge amount of starvation.”
“Other species may have moved in to take advantage of it, and then when the heat wave passed, things are maybe a bit more back to normal – although the crabs have a long road to getting past that even in normal times.”
The disappearance of snow crabs around Alaska is a distressing sign of how marine life is being affected by climate change.
Szuwalski told CNN what’s happening with Alaska’s crabs is proof that the climate crisis is rapidly accelerating and impacting livelihoods.
“The big take home for me from the paper, and just the whole experience in general, is that historically, fishery scientists had been very worried about overfishing – this has been our white whale, and in a lot of places we really solved that with management,” Szuwalski said.
“But climate change is really throwing a wrench into our plans, our models and our management systems.”
The study is published in the journal Science.
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