I don't know much about snow crab but Dungeness and various oysters in the Pacific Northwest US are threatened by rising ocean acidity caused by increased CO2. Warmer water is also allowing green crabs to take hold. Farther south urchins have killed off a lot of kelp forest in a way that seems not to self-correct. Easy to imagine there are similar problems all over the ocean.
At least the urchin problem is caused, in part, by the mysterious sea star wasting disease - a disbiosis of their microbial layer that leads to rapid death. Sea stars are the natural predators of the urchins, and with their disappearance, the urchins flourish and take down the kelp.
I think it's just the western coast of North America that has this problem, rather than the entire Pacific. For example in New Zealand, which is in the Pacific, there were never any sea otters. Urchins, regarded locally as a delicacy, are not particularly abundant.
