As you might expect, quite a few species are covered by the term, but for fishmongers what is generally meant is a tight-knit group of a few species from the Northern Pacific. Named after the rocky bottoms where they congregate to eat herring and crustaceans, the Alaskan Rockfish is a sought-after sport fish which looks something like a bright orange grouper. As they grow larger, they move to deeper waters. With large flakes and a mild but distinctive flavor, you can prepare it in a variety of ways. Might I suggest a blush wine? I do.