I’ve been keeping an eye on the story of the snow crab population crash for a couple of months now, and as someone interested in shellfish from both a culinary and an environmental standpoint, I’m getting a bit concerned! The NOAA (the National
Oceanic and Atmospheric Association, the American body in charge of the crabs’ habitats and fishing thereof) is gesturing vaguely to climate change to blame for October’s cancellation of Bering Sea snow crab season because 11 billion crabs had basically up and disappeared. But, thanks to a new analysis by Nautilus, it seems things the situation is far more complicated. And it has everything to do with math.
The tale spun by Spencer Roberts is worth the full read, but the gist is as follows: Officials—and fishers—may be repeating history; Spencer cites the 1980s crash of a similar species, the Alaskan king crab, as precedent. Then, as now, it may come down to an ignorance of the crabs’ natural behaviours. Testing nets can drag through a huge pod of hundreds of crabs (that gather in dome-like piles to rest between foraging sessions) and then that highly concentrated number can be erroneously extrapolated to an entire area. This may mean that the 11 billion death toll may be overinflated because there were never that many crabs, to begin with.
“ This opens the possibility for inflated population estimates if surveys happen to intersect aggregations of crabs. That may have happened twice with king crabs: their Cold War collapse in the Bering Sea was preceded by a “recruitment pulse”—a cohort of maturing males—that motivated regulators to double catch limits every three years. […]
“We know that recruitment boom was real,” [NOAA’s Alaska Fisheries Science Center program manager Mike] Litzow responded when asked about the possibility that survey methods had caused crab populations to be overestimated. He cited crab reproductive cycles, improved survey coverage, and the fact that the boom persisted for two consecutive years. But while a pulse did occur, was it truly as large as the models suggested? And should NOAA regulators have raised catch limits when its assessments also suggested that the abundance of harvest-sized males had dropped by half in the decade prior?”
Spencer falls heavily on the “No” side here, but the situation gets tragic for the fishers involved, who sank their livelihood into an industry that may have never been robust enough to take it. The crabs themselves got the shorter end of the stick; the limits raised to harvest crabs that didn’t exist truly decimated the ones that did. Only time will tell if populations can recover—it might be worth voting with our dinner plates over.