The Collaborative International Dictionary of English v.0.48:

perch \perch\ (p[~e]rch), n. [Written also pearch.] [OE.
   perche, F. perche, L. perca, fr. Gr. pe`rkh; cf. perkno`s
   dark-colored, Skr. p[.r][,c]ni spotted, speckled, and E.
   freckle.] (Zool.)
   1. Any fresh-water fish of the genus Perca and of several
      other allied genera of the family Percid[ae], as the
      common American or yellow perch (Perca flavescens syn.
      Perca Americana), and the European perch (Perca
      fluviatilis).
      [1913 Webster]

   2. Any one of numerous species of spiny-finned fishes
      belonging to the Percid[ae], Serranid[ae], and related
      families, and resembling, more or less, the true perches.
      [1913 Webster]

   Black perch.
      (a) The black bass.
      (b) The flasher.
      (c) The sea bass.

   Blue perch, the cunner.

   Gray perch, the fresh-water drum.

   Red perch, the rosefish.

   Red-bellied perch, the long-eared pondfish.

   Perch pest, a small crustacean, parasitic in the mouth of
      the perch.

   Silver perch, the yellowtail.

   Stone perch, or Striped perch, the pope.

   White perch, the Roccus Americanus, or Morone
      Americanus, a small silvery serranoid market fish of the
      Atlantic coast.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Ruff \Ruff\, Ruffe \Ruffe\, n. [OE. ruffe.] (Zool.)
   A small freshwater European perch (Acerina vulgaris); --
   called also pope, blacktail, and stone perch, or
   striped perch.
   [1913 Webster]