threadfin

from WordNet (r) 3.0 (2006)

threadfin
    n 1: mullet-like tropical marine fishes having pectoral fins
         with long threadlike rays

from The Collaborative International Dictionary of English v.0.48

Threadfin \Thread"fin`\, n. (Zool.)
   Any one of several species of fishes belonging to {Polynemus}
   and allied genera. They have numerous long pectoral
   filaments.
   [1913 Webster]