I live in the midwest and recently read a few articles on buying shrimp. They all basically said unless you are on a coast somewhere to buy frozen shrimp as it is all flash frozen and what you see in the case is previously frozen shrimp that has been thawed out and sold as fresh. Frozen is usually cheaper as well.
I've started to wonder, given where I live, if frozen seafood is the way to go or if I should still look for fresh. I don't really have a "fishmonger" where I live. If I buy seafood it is usually out of a case in the supermarket. I like seafood but I'm always leery of buying it around here. Funny thing is I'll see go out for sushi around here and often wonder where they get their supply from.