ANCHORAGE, Alaska (KTUU) - An increase in temperature changes in the Bering Sea is linked to the decline of snow crabs, according to ongoing studies from the National Oceanic and Atmospheric Administration (NOAA).
Snow crabs are highly stenothermic, or only equipped to survive across a narrow range of cold water temperatures. According to NOAA, the species thrive best in waters 2 degrees Celsius and below.
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From 2018 to 2019, NOAA recorded Bering Sea temperatures at over 3 degrees Celsius. The water temperature spiked from 1.52 degrees in 2017 to 3.50 degrees in 2018. The following year, in 2019, the warm waters remained, with an average temperature of 3.33 degrees, roughly two degrees higher than the recorded average seen over the past two decades.
“In those two years, 2018 and 2019, the Bering Sea was very warm,” Ben Daly, with the Alaska Department of Fish and Game, said.
In 2019, ADFG recorded the crabs’ highest mortality rate.
“The belief is that those warm conditions were detrimental to the population,” Daly said. “There was a high, natural mortality event that occurred in 2018 and 2019.”
The water temperature fell again under 2 degrees in 2022. At 1.00 degrees, it was the lowest recorded temperature since 2013.
Ongoing studies from NOAA indicate there could be a direct correlation between the high temperatures seen in the Bering Sea and the now-vanishing snow crab population — but researchers aren’t sure why just yet. They are predicting that the high temperatures could be causing an indirect — or even direct impact — on the crabs.
“If temperature increases the incidence of disease, more snow crab could die off from disease,” NOAA Fisheries Research Biologist Erin Fedewa said. “If temperature impacts the spatial distribution of predators, like Pacific cod, then in a warm year they could be able to shift their distribution to overlap with snow crab, which is a key prey item.”
One of the other theories, Daly explained, is starvation. According to Daly, the changing temperatures could have caused an increase in the crabs’ metabolism.
“The belief is that with those warm temperatures, there simply wasn’t enough food available to them and there was starvation effects,” Daly said.
The Department of Fish and Game says there will need to be a continuous trend of cold water in the Bering Sea before an increase in the snow crab populations is possible. Last year, NOAA reported for the first time since 2017, temperatures below 2 degrees Celsius.
“We saw one bright spot in 2022 Eastern Bering Sea survey data, we did see (a) signal of juvenile snow crab in the population,” Daly said. “So, the babies are there.”
According to Daly, it will take years for the population to rebound.
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