The Collaborative International Dictionary of English v.0.48:

Leuciscus \Leuciscus\ prop. n.
   A genus of freshwater fishes including the dace (Leuciscus
   leuciscus).

   Syn: genus Leuciscus.
        [WordNet 1.5]

The Collaborative International Dictionary of English v.0.48:

Dace \Dace\ (d[=a]s), n. [Written also dare, dart, fr. F. dard
   dase, dart, of German origin. Dace is for an older darce, fr.
   an OF. nom. darz. See Dart a javelin.] (Zool.)
   A small European cyprinoid fish (Leuciscus leuciscus,
   formerly Squalius leuciscus or Leuciscus vulgaris); --
   called also dare.
   [1913 Webster +PJC]

   Note: In America the name is given to several related fishes
         of the genera Squalius, Minnilus, etc. The
         black-nosed dace is Rhinichthys atronasus the horned
         dace is Semotilus corporalis. For red dace, see
         Redfin.
         [1913 Webster]

WordNet (r) 3.0 (2006):

Leuciscus leuciscus
    n 1: small European freshwater fish with a slender bluish-green
         body [syn: dace, Leuciscus leuciscus]