The Collaborative International Dictionary of English v.0.48:

Bluefish \Blue"fish`\, n. (Zool.)
   1. A large voracious fish (Pomatomus saitatrix), of the
      family Carangid[ae], valued as a food fish, and widely
      distributed on the American coast. On the New Jersey and
      Rhode Island coast it is called the horse mackerel, in
      Virginia saltwater tailor, or skipjack.
      [1913 Webster]

   2. A West Indian fish (Platyglossus radiatus), of the
      family Labrid[ae].
      [1913 Webster]

   Note: The name is applied locally to other species of fishes;
         as the cunner, sea bass, squeteague, etc.
         [1913 Webster]