If we're talking "must go" and seafood in Portland, I'd be looking at Fore Street. Far from a "seafood" restaurant, it has enough on the menu to satisfy most fish cravings. For a pure seafood play their sister restaurant Street and Company. If you like really mind blowing sushi, Miyake is the place. This is not your run of the mill sushi place.
288 Fore Street, Portland, ME 04101