1) Fish 
• (n.) A roachlike European fish (Rhodima amarus).
(Rhodeus), any of several small, carplike fish of the family Cyprinidae noted for their unusual manner of breeding. Native to clear, stony streams ... [1 related articles]
Bit'ter·ling noun [ G.] (Zoology) A roachlike European fish ( Rhodima amarus ). 
a cyprinid fish, Rhodeus sericeus, found in central and eastern Europe, the female of which has a long, bright yellow or red ovipositor to deposit eggs in the mantle cavity of mussels.