Is this a surprise? Even though the claw can grow back, it's not good for the crab to break off a claw.
Some crab fisheries are called sustainable because they only take a claw and throw back the rest of the crab. Well, now researchers have discovered that breaking off a claw can be harmful to the crabs.
I guess there's a reason crabs have claws, and the crabs would prefer not to have pieces broken off. This doesn't completely overturn the sustainability argument, crabs have a better chance of surviving loss of a claw than being cooked whole. But it's a bit too easy to assume everything's fine if the crab gets thrown back.
I wonder if an ecological study would show that clawless crabs have trouble even if they survive the shock? This study didn't look at survival value of claws, it only looked at death from the direct injury of claw removal.