The Collaborative International Dictionary of English v.0.48:

Scup \Scup\, n. [Contr. fr. American Indian mishc[`u]p, fr.
   mishe-kuppi large, thick-scaled.] (Zool.)
   A marine sparoid food fish (Stenotomus chrysops, or
   Stenotomus argyrops), common on the Atlantic coast of the
   United States. It appears bright silvery when swimming in the
   daytime, but shows broad blackish transverse bands at night
   and when dead. Called also porgee, paugy, porgy,
   scuppaug.
   [1913 Webster]

   Note: The same names are also applied to a closely allied
         Southern species (Stenotomus Gardeni).
         [1913 Webster]

WordNet (r) 3.0 (2006):

Stenotomus chrysops
    n 1: found in Atlantic coastal waters of North America from
         South Carolina to Maine; esteemed as a panfish [syn:
         scup, northern porgy, northern scup, Stenotomus
         chrysops]