First, VA and MD greatly reduced the crab allotment for 2009.

The commercial way of generating softshell crabs:
the crabs that will molt in the next few days are put in separate holding pens, and separated from each other.
http://www.bluecrab.info/redsign.htm
shows which crabs to put in the pens.

after molt, the crabs are refrigerated, and shipped through channels to final destination. properly handled, they arrive in the kitchen live.(i guess dead is spoiled).

the only "season" is that molting starts in mid/late May. molting takes place every 10-20 or so days.

the shortage in soft shell crabs is probably due to the shortage on the Chesapeake.

it is by the way illegal for private parties to hold crabs for molting.