[image:noaa.gov]

That’s not a typo, a whopping 10 billion snow crabs went AWOL.

Between 2018 and 2021, this massive amount of snow crabs vanished from the waters of Alaska, accounting for almost 90% of the population in the area. It was so bad that Alaska had to postpone its snow crab harvest in 2022 and again in 2023 because of the unusual die-off.

But what happened to the eastern Bering Sea’s snow crabs (Chionoecetes opilio)? Scientists have been trying to figure out what caused the cold water-loving crustaceans to disappear as fishermen and the people who depend on the crabs for a living are left unsure about their future.

Now, an explanation may have been found.

According to a paper published this week in the journal Science, researchers believe the crabs probably starved to death as a result of the marine heat waves in 2018 and 2019. Besides the heat waves, it also appears as if their breeding success may have outstripped the food available to support the crab colonies.

“It’s a fishery disaster in the truest sense of the word,” says study co-author Cody Szuwalski, a biologist at the National Oceanic and Atmospheric Administration (NOAA).

Tanner crabs, sometimes known as snow crabs, flourish in the Bering Sea’s freezing waters, where the average bottom temperature is below 1 Degree Celcius. Although tests show they can survive in temperatures as high as 11 Degrees Celcius, they are forced to consume more calories as the water temperature rises.

A booming population and increased need for calories forced the snow crab to literally eat itself into a population collapse. This theory is further supported by the fact that crabs caught after the heat wave began had smaller body sizes than those caught years prior.

According to Szuwalski, “From 2017 to 2018, the calories they needed quadrupled.”

In a double tragedy, other species that usually never ventured into the crab’s frigid territory suddenly found the water much more to their liking and further drove down numbers as they fed on the crabs.

Besides the crabs, salmon, seabirds and seal populations have also declined according to the research paper.

“We are now witnessing more and more big crashes associated with extreme temperatures.”

Some animals however, such as sablefish and walleye pollock, flourished as a result of the increased water temperatures.

This shows that some species are adaptable to significant environmental changes more quickly than others. However, the overall mix of species dwelling in the Bering Sea will probably look very different than it does at the moment if ocean temperatures continue to rise.

For now, there doesn’t seem to be any danger of snow crabs going extinct, and as other species do, they will likely relocate to areas where the water suits them better. What this does however prove I that conservationists will have to factor in changing temperatures when drawing up conservation models.

Things are looking a bit crabby for our marine life at the moment, but according to biologists, the snow crab population should bounce back in four years or so. Hopefully.

[source:smithsonianmagazine]