The Collaborative International Dictionary of English v.0.48:

Redfish \Red"fish`\ (r[e^]d"f[i^]sh`), n. (Zool.)
   (a) The blueback salmon of the North Pacific; -- called also
       nerka. See Blueback
   (b) .
   (b) The rosefish.
   (c) A large California labroid food fish (Trochocopus
       pulcher); -- called also fathead.
   (d) The red bass, red drum, or drumfish. See the Note under
       Drumfish.
       [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Nerka \Ner"ka\, n. [Russ. niarka, prob. fr. native name.]
   (Zool.)
   The most important salmon of Alaska (Oncorhinchus nerka),
   ascending in spring most rivers and lakes from Alaska to
   Oregon, Washington, and Idaho; -- called also red salmon,
   redfish, blueback, and sawqui.
   [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

redfish
    n 1: North Atlantic rockfish [syn: redfish, rosefish, ocean
         perch]
    2: large edible fish found off coast of United States from
       Massachusetts to Mexico [syn: red drum, channel bass,
       redfish, Sciaenops ocellatus]
    3: male salmon that has recently spawned