I did a decent amount of research into this a while back. They (blue crabs) can be grown in captivity, but they’re cannabalistic, so they have to be kept apart from each other. This makes it pretty inefficient and high overhead. The crab farming operations I’ve seen literally have each crab in its own little compartment - this is too labor intensive to be feasible outside of places with very low wages like the Philippines and Indonesia.

If someone can figure out how to keep crabs in large pens without them eating each other, they will make a lot of money. I’m not sure if that’s possible with selective breeding. Maybe we need to wait until crab legs can be “printed” or grown in a lab