In October 2022, a popular post to Reddit’s r/news indicated that Alaska’s regular snow crab season was canceled, pending investigation into the cause of a major problem:
The post on r/news linked to a CBS News article, published on October 13 2022. It began with an acknowledgement that 2022 marked the first time ever that the Alaska Department of Fish and Game had canceled the winter snow crab season because of a 90 percent decline in snow crab numbers:
In a major blow to America’s seafood industry, the Alaska Department of Fish and Game has, for the first time in state history, canceled the winter snow crab season in the Bering Sea due to their falling numbers. While restaurant menus will suffer, scientists worry what the sudden population plunge means for the health of the Arctic ecosystem.
An estimated one billion crabs have mysteriously disappeared in two years, state officials said. It marks a 90% drop in their population.
One of the top comments on the thread came from a self-identified marine biologist, speculating how temperature changes in crab habitats could lead to population collapse:
As [another commenter] said, water of that depth takes a while to heat up and is very good at keeping a steady temperature, with temp changes happening over months from season to season. A lot of marine life is, therefore, sensitive to changes of even a couple degrees (particularly an increase) and have a temp band they are comfortable at. In fact, there are a number of fish species, for example, that use temperature gradients to navigate to their breeding grounds in the North Sea.
So, keeping this in mind, when you add climate change, what’s happening is that over the long term, the band of water temp that the crabs live in, for example, has shifted upwards by a degree or so (please don’t quote me on the numbers, I don’t have references to hand and I am very much generalising to put a point across). Suddenly, come summer, the water temp has increased to beyond what they can handle, even by a degree is too much. If it was a short term increase, most marine species are quite resilient and will cope. But if that water temp increase lasts over months, and then into years (because that is what climate change is all about) you then have a population that is placed under long term stress. This reduces feeding and breeding. Add in other stressor such as acidification (Inc in water temp shifts the carbonate chemical equation equilibrium), reduction in prey, overfishing, etc and you have a population collapse.
Source – I’m a marine biologist who’s avoiding finishing her work presentation and is browsing reddit instead.
I’m a biologist working on this crab stock. The Bering Sea experienced a series of “marine heat waves” from 2016-2021 that are thought to be the initial cause of stress. The question is how did crab respond. Hypotheses include:
- Moving to deeper (unfished) waters or north (across the Russian border where our surveys don’t go).
- Stress on their prey supply (especially for the young crab), when the crabs are hungrier due to warmer waters. The Bering Sea is overall more productive when there’s more ice (colder).
- Predators (fish like cod) moved north into their waters in greater numbers, so there was more predation pressure. And when water is warmer, increased metabolism means these fish are hungrier.
- Stress-induced disease.
It’s likely not ocean acidification, that’s a worry for the future but it doesn’t seem to be bad enough yet.
edit one point worth making is that the actual shutdown is fisheries management “working as intended” to protect the stock. Very hard and terrible, and a huge surprise exacerbated by the fact that covid cancelled our 2020 surveys just when things were probably going bad. But (unlike, say, the cod collapses in the 1990s) the science was listened to without political pushback, so at least there’s some good chance of resilience to the extent that the climate allows.
An October 12 2022 Alaska Public Media article covered the decision and quoted career fishers who had observed changes in marine populations:
For the first time ever, the Bering Sea snow crab fishery will not open for the upcoming season. Alaska’s Department of Fish and Game announced the closure Monday [October 10 2022]. The Bristol Bay red king crab fishery will also be closed this year  — for a second year in a row [after 2021].
Gabriel Prout co-owns the F/V Silver Spray with his dad and brothers. The Silver Spray is a 116-foot steel crabber that’s homeported in Kodiak.
He said he wasn’t surprised that Fish and Game closed the king crab fishery — in a normal year, he’d go out for king crab, too. But numbers have been on the decline and that fishery didn’t open last year , either.
“The real shocking part is the total and complete collapse of the snow crab fishery which no one expected last year  when it happened, and a complete closure this year was equally as shocking,” Prout said.
An October 16 2022 CNN.com article quoted officials on the decision, explaining that rapid climate change was a suspected cause:
… Mark Stichert, the groundfish and shellfish fisheries management coordinator with the state’s fish and game department, said that more crab were being fished out of the oceans than could be naturally replaced.
“So there were more removals from the population than there were inputs,” Stichert explained at [an October 2022] meeting.
Between the surveys conducted in 2021 and 2022, he said, mature male snow crabs declined about 40%, with an estimated 45 million pounds left in the entire Bering Sea.
“It’s a scary number, just to be clear,” Stichert said.
But calling the Bering Sea crab population “overfished” – a technical definition that triggers conservation measures – says nothing about the cause of its collapse.
“We call it overfishing because of the size level,” Michael Litzow, the Kodiak lab director for NOAA Fisheries, told CNN. “But it wasn’t overfishing that caused the collapse, that much is clear.”
Bloomberg.com also quoted Litzow in October 17 2022 reporting, with respect to the cause of the issue and the longer-term effects on fisheries:
“We’re still trying to figure it out, but certainly there’s very clear signs of the role of climate change in the collapse,” said Michael Litzow, shellfish assessment program manager at the National Oceanic and Atmospheric Administration (NOAA), which runs an annual survey of Bering Sea snow crab numbers. (Snow crabs are also found in the Beaufort and Chukchi seas off Alaska.)
“There are some signs of another wave of really small crabs coming into the survey, and so looking out four to five years from now, those crabs, if they survive, would be coming into the fishery. So that’s the bright news,” Litzow said. “But if you’re trying to pay off a boat loan or keep a team employed, five years is a really long time.”
An October 14 2022 article in the New York Times included a comment from Alaska-based biologist Miranda Westphal, who described environmental changes affecting crab populations, but said that determining the precise cause was difficult — due to the absence of the crabs:
“From 2018 to 2021, we lost about 90 percent of these animals,” Ms. Westphal said.
Alaska is the fastest warming state in the United States, according to Climate Central, an independent group of scientists who research and report about changing climate. And rising temperatures in Alaska’s cold waters may be killing the crustaceans
“They probably starved to death and there was not enough food,” she said.
Ms. Westphal said disease could have also been a factor.
“We don’t know and we are never going to actually know because the crabs are gone,” she said.
A popular October 2022 post to Reddit’s r/news reported that the Alaska Department of Fish and Game canceled snow crab season for the first time in history because of the sudden collapse of snow crab stocks, by 90 percent. The claim was accurate, with scientists and officials suspecting warming waters, climate change, and potential overfishing as the likeliest causes for for the population collapse.