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Where Have All the Snow Crabs Gone?

Dew would log 943 dives observing the crabs during his 25-year tenure as a marine biologist at NOAA, where he studied their complex social systems, cooperative foraging techniques, and unique podding behavior: when king crabs come together in daytime to rest in spherical or dome-shaped formations before foraging in a herd at night. Unlike 1 billion heat wave casualties in the shallow and intertidal zones of the Salish Sea last year, snow crabs live on seafloors in deeper waters, and there are no records of water temperatures high enough to kill crabs directly. As sea ice forms in winter, salt is expelled and cold, dense water sinks to the floor of the Bering continental shelf, forming what oceanographers call the "Cold pool." This is where young snow crabs grow up with abundant food, protected by water that is too cold for many of their predators-until now. In many years past, cold pool conditions didn't form in the Eastern Bering Sea, yet snow crabs fared well. Snow crabs are plagued by a parasitic alga called Hematodinium. Geographical data show that the historical winter habitat of snow crabs overlaps with recent vessel movements,5 which in some cases have pushed into the snow crab "Hotspot" near St. Matthew Island, a landmass usually locked in ice through winter. While snow crabs don't form proper pods like king crabs do, they still aggregate in large groups and are patchily distributed across the seascape, creating the potential to overestimate crab populations. In strikingly similar form, between 2015 and 2018 NOAA surveys reported a 2,000 percent increase in recruitment of male snow crabs. Several of the council's high-ranking government officials, including the director who oversaw the recent snow crab crash, have gone on to work for companies with large Bering Sea trawling operations.

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