Don't know if any of you have ponds on your property but I just stumbled onto this article while looking for something else. Now this is from 2008 so if it has already been posted please forgive. http://scienceblogs.com/clock/2008/10/can_you_raise_seawater_blue_cr.php
Apparently yes: Freshwater Farm Ponds Turning into Crab Farms:
North Carolina's native blue crab population has been at historic lows since 2000. Dr. Dave Eggleston, director of NC State's Center for Marine Sciences and Technology (CMAST) and professor of marine, earth and atmospheric sciences, looked at various methods for helping the population recover. He hit upon a solution which not only reduces pressure on existing crab populations, but also benefits farmers looking to diversify their crops: using irrigation ponds on farms to grow blue crabs.
Eggleston and his fellow researchers discovered that crabs can tolerate a salinity level of only .3 parts per thousand, which is about the same level found in coastal tap water. They did further work to determine the best set of circumstances for raising crab: population density, food rations, and habitat structure in ponds.
This past July, Eggleston and Ray Harris, NC State director of cooperative extension for Carteret County, had the opportunity for a large-scale test when they stocked a 10-acre lake with 40,000 hatchery-raised crabs, and a smaller pond with 4,000 crabs. The crabs will take approximately 105 days to reach maturity, and so far the endeavor looks successful.
With the rapid rate of growth for pond-raised crabs, Eggleston expects that in a given year, a farm could produce two to three harvests, as crabs don't do well in freshwater during the winter months.
"If you look at a 2 1/2 -acre pond, you could stock it with 50,000 hatchery-raised crabs and expect to harvest around 20 percent, or 10,000 fully grown crabs. At $3 per crab, that's $30,000 - and multiply that times three. It definitely adds up."
So...it's been a while...anyone give it a try yet?