The Collaborative International Dictionary of English v.0.48:

Cobia \Co"bi*a\, n. (Zool.)
   An oceanic fish of large size (Elacate canada); the
   crabeater; -- called also bonito, cubbyyew, coalfish,
   and sergeant fish.
   [1913 Webster]

WordNet (r) 3.0 (2006):

sergeant fish
    n 1: large dark-striped tropical food and game fish related to
         remoras; found worldwide in coastal to open waters [syn:
         cobia, Rachycentron canadum, sergeant fish]