What caused the great snow crab collapse?

NOAA's Alaska Fisheries Science Center sent this today:

In a new paper published in Nature Climate Change, NOAA Fisheries scientists attribute the abrupt collapse of snow crab to borealization, or an ecological shift from Arctic to sub-Arctic conditions during the marine heatwave in 2018-2019 in the southeast Bering Sea due to human-caused climate change. Scientists determined that climate change affects crabs at different life stages. A combination of factors, all associated with borealization, likely played a role in the decline including a decrease in sea ice, increase in the prevalence of bitter crab disease, which can be fatal for snow crabs, increased Pacific cod abundance (snow crab predator) and prey limitations. Scientists ruled out trawl fisheries bycatch to explain the mortality associated with the collapse because the estimated bycatch is orders of magnitude too small to explain this level of mortality. Results indicate that over the next 1-2 decades, the Arctic characteristics necessary for the snow crab stock may become scarce in the southeastern Bering Sea.