In molting the crab forms a new shell under the old and the knowledgeable bayman or commercial crabber recognizes the pre-molt stages up to two weeks before the shed. They are still feeding and cannot be kept in a crab car with crabs likely to be shedding because they will eat their soft, vulnerable brethren. Generally the softie becomes a paperback in about nine to 12 hours and the tinback stage is achieved in about 12 to 24 hours. The crab is its old, hard, pugnacious self about three days later. The time between molts varies with the size and nutrition of the crab, the temperature and salinity of the water, the amount of light and other factors.
Older crabs molt less frequently than younger ones.
Males will molt about 21 to 22 times in a normal lifespan and females will molt 18 to 20 times. Crabs have the interesting ability to regenerate appendages if they lose them. A miniature claw will form, for instance, if one is lost, and in the next successive molts it will reach normal size again. The soft crab, considered by many to be the ultimate in seafood eating pleasure, is eaten in almost its entirety. All that is removed are the gills, apron, eyes and stomach and mouth parts.