In the Sunday, Juneau Empire, there was a photo and article about the tanner crab annual molt. We went down to the North Douglas boat launch to see all the empty shells. The crabs leave their shells and start growing their new ones as they grow bigger. From the article in the newspaper:
A crab preparing to molt pulls the minerals out of its shell into its bloodstream. It takes in water, which makes it swell in size. The swelling splits the crab down its back, right down the line where a human would to clean it. Then the crab backs out of its shell - carefully. Exiting takes between 10 minutes and a half-hour, Bishop said.I'll have to find out how long it takes the naked crabs to grow their shells back – it seems like it leaves them very vulnerable until they have their protective shell back.
There were piles of shells–its just too bad we weren't around when the meat part was there!