You can do this. Prawns have to go to salt/brackish water to breed in a very smilar way. You can simiulate this in a stand wave tank, and use the southern climate to simulate a longer growing season.
Then, as they appear to tolerate crowding, grow out the same way they are doing the shrimp just outside Vegas. Sure if you're increasing supply, sooner or later the market will come down....so what if it drops a few hundred. It's thousands on the lb. Clearly rate of return is better than the channel or tilapia are. And even better than my prized $20/lbs live prawns.
Let me do some more tinkering.
Anyone know were I can get fingerlings?