A bait ready shedder will split by lightly squeezing underneath the crab's top shell points. A close to bait ready crab will bend, but not actually split, and goes back into the water for a later check. Ok, now you have a bait ready shedder. An average size shedder can be cut up into 17 baits. It's the pheromones.
Pheromones are a chemical substance secreted by crabs and other creatures to attract each other.
The shedder crabs pheromone signature also draws every fish in the sea, specifically weakfish. Once a crab sheds and becomes a soft shell, it is still good bait, but it looses its pheromone potency and does not work as well as a bait ready peeler. Only a small piece of shedder crab is required for bait, because you are fishing with pheromones rather then meat. Since a fresh piece of shedder will have more scent, it necessary to change the bait regularly. This is also true with other kinds of bait.