I'm in MA. I've been buying fish from a fishermen's co-op based in Gloucester. We get whatever they caught that day (works like buying shares in a co-op farm). I do this primarily to support the fishermen and their families as the fish here in MA is universally good. I'd chalk that up to the sellers providing what consumers expect - and in New England, we expect good fish.

That said, never hesitate to smell fish before you buy. If it's behind glass, ask the salesperson to let you smell it. This is expected (at least here in N.E.). If it smells like fish, you know what to do.

Also, don't buy fish for more than a day or so ahead; it keeps better in the almost frozen high-humidity environment that comes with being kept on crushed ice - and your fridge isn't going to provide that.