Buying fresh and local
Always ask your fishmonger what is the most local seafood on hand and you're likely to get the freshest and responsibly-caught fish choice. Supporting your local fishery is the best, but knowing where the seafood comes from will allow you to expand your palate to another region for seafood.
Note that 'local' can mean from North America and South America. Our government is ever watchful of responsibly-caught practices from border fisheries and beyond.
To learn more about tracing seafood here are just a few websites to visit: Seafood Watch, This Fish, Eat Gulf Seafood, Fish Choice, SeaChoice.