The Collaborative International Dictionary of English v.0.48:

Sea bass \Sea" bass`\ . (Zool.)
   (a) A large marine food fish (Serranus atrarius syn.
       Centropristis atrarius) which abounds on the Atlantic
       coast of the United States. It is dark bluish, with black
       bands, and more or less varied with small white spots and
       blotches. Called also, locally, blue bass, black sea
       bass, blackfish, bluefish, and black perch.
   (b) A California food fish (Cynoscion nobile); -- called
       also white sea bass, and sea salmon.
       [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Tautog \Tau*tog"\, n. [The pl. of taut, the American Indian
   name, translated by Roger Williams sheep's heads, and written
   by him tauta['u]og.] (Zool.)
   An edible labroid fish (Haitula onitis, or Tautoga
   onitis) of the Atlantic coast of the United States. When
   adult it is nearly black, more or less irregularly barred,
   with greenish gray. Called also blackfish, oyster fish,
   salt-water chub, and moll. [Written also tautaug.]
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Blackfish \Black"fish\, n.
   1. (Zool.) A small kind of whale, of the genus
      Globicephalus, of several species. The most common is
      Globicephalus melas. Also sometimes applied to other
      whales of larger size.
      [1913 Webster]

   2. (Zool.) The tautog of New England (Tautoga).
      [1913 Webster]

   3. (Zool.) The black sea bass (Centropristis atrarius) of
      the Atlantic coast. It is excellent food fish; -- locally
      called also black Harry.
      [1913 Webster]

   4. (Zool.) A fish of southern Europe (Centrolophus
      pompilus) of the Mackerel family.
      [1913 Webster]

   5. (Zool.) The female salmon in the spawning season.
      [1913 Webster]

   Note: The name is locally applied to other fishes.
         [1913 Webster]

WordNet (r) 3.0 (2006):

blackfish
    n 1: large dark-colored food fish of the Atlantic coast of North
         America [syn: tautog, blackfish, Tautoga onitis]
    2: female salmon that has recently spawned
    3: small dark-colored whale of the Atlantic coast of the United
       States; the largest male acts as pilot or leader for the
       school [syn: pilot whale, black whale, common
       blackfish, blackfish, Globicephala melaena]