"The terminology is sometimes confusing as the distinction between "shrimp" and "prawn" is sometimes blurred. Recent aquaculture literature increasingly uses the term "prawn" only for the freshwater forms of palaemonids and "shrimp" for the marine penaeids.
SO, if you don't know your palaemonids from your penaeids, you're in deep DoDo!
Also from Wikipedia:
"The global annual production of freshwater prawns in 2003 was about 280,000 tonnes, of which China produced some 180,000 tonnes, followed by India and Thailand with some 35,000 tonnes each. Other major producer countries are Taiwan, Bangladesh, and Vietnam. In the United States, there are only a few hundred small farms for M. rosenbergii with an overall production of just about 50 tonnes in 2003. The U.S. is, though, the largest producer of farmed crayfish. In 2003, U.S. farms produced 33,500 tonnes of red swamp crawfish (Procambarus clarkii), a crayfish species native to North America."
HOWEVER, the best shrimp come from the good ol' Gulf Coast of the U.S., by God, A. Just ask Forrest Gump!