Warming of the waters is the “key culprit” in the mass death of Alaskan crabs

According to an annual survey of the Bering Sea floor by the National Oceanic and Atmospheric Administration, estimates for the total number of crustaceans dropped to about 1.9 billion in 2022, up from 11.7 billion in 2018.

According to experts, climate change is a prime suspect in the mass death of Alaska spider crabs, after the state took the unprecedented step of canceling their crop this season to save the species.

According to an annual survey of the Bering Sea floor conducted by the National Oceanic and Atmospheric Administration, estimates for the total number of crustaceans dropped to about 1.9 billion in 2022, down from 11.7 billion in 2018, or a reduction of approximately 84%.

For the first time ever, the Alaska Department of Fisheries and Game announced that the Bering Crab season will remain closed for 2022-23, stating in a statement that efforts must move to “conservation and reconstruction. given the conditions of the stock “.

The species is also found in the northernmost Chukchi and Beaufort Seas, but does not reach feasible size there.

Erin Fedewa, a marine biologist at the Alaska Fisheries Science Center, told AFP that the shocking numbers seen today were the result of the heatwaves in 2018 and 2019.

“The cold water habitat they need was virtually absent, which suggests that temperature is indeed the main culprit in this population decline,” he said.

Historically an abundant resource in the Bering Sea, their loss is seen as a wake-up call for ecological disruption.

This undated photo courtesy of NOAA Fisheries shows Erin Fedewa, a marine biologist from Alaska Fisheries Science Ce

This undated photo courtesy of NOAA Fisheries shows Erin Fedewa, a marine biologist at the Alaska Fisheries Science Center, standing next to baskets of snow crabs on the back deck of an Alaskan survey ship.

There are thought to be several ways in which warmer temperatures have depleted the species.

Studies have indicated a higher prevalence of bitter crab disease when the temperature warms up.

Crustaceans, so named for their love of cold water, are also subjected to greater metabolic stress in warmer waters, meaning they need more energy to stay alive.

“A working hypothesis right now is that the crabs were starving, they couldn’t keep up with metabolic demands,” Fedewa said.

Young snow crabs, in particular, need cold temperatures to hide from their main predator, the Pacific cod, and temperatures in regions where juveniles typically reside went from 1.5 degrees Celsius in 2017 to 3, 5 degrees Celsius in 2018 (35 degrees Fahrenheit to 38 degrees Fahrenheit), with studies indicating 3C could be an important threshold.

Overfishing is not blamed

More research is underway and the results are expected to be published soon, but in the meantime “everything really points to climate change,” Fedewa said.

This undated photo courtesy of NOAA Fisheries shows a person measuring young snow crabs on the deck of an investigation vessel

This undated photo courtesy of NOAA Fisheries shows a person measuring young snow crabs on the deck of an Alaskan survey ship.

“These are truly unprecedented and troubling times for Alaska’s iconic crab fishing and hardworking fishermen and communities that depend on them,” said Jamie Goen, executive director of Alaska Bering Sea Crabbers, complaining that the crab second and third generation – fishing families will “fail”.

The industry was also affected by the cancellation of the Bristol Bay red king crab fishery for the second consecutive year.

Fedewa also noted that overfishing is not a major factor in the collapse of the spider crab population.

Fishing only removes large adult males, he said, “and we’ve seen these declines in all sizes of spider crab, which really suggests an environmental factor is at play from below.”

Male Alaska snow crabs can reach six inches (15 centimeters) in shell width, but females rarely grow larger than three inches, according to NOAA.

In some good news, this year’s survey saw a significant increase in immature crabs over last year, but it will take four to five years for the males among them to become fishable in size.

After the years of the heat wave, temperatures have returned to normal and “the hope is that leaving the crabs intact will allow them to reproduce, there will be no mortality and we can simply let the stock try to recover,” Fedewa said.

A hope that is pinned on no further heat waves.


Valuable crab populations are on a “very frightening” decline in the warming of the Bering Sea


© 2022 AFP

Citation: Water warming “key culprit” in Alaska mass crab death (2022, Oct 19) recovered Oct 19, 2022 from https://phys.org/news/2022-10-key-culprit-alaska-crab -mass.html

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