The Collaborative International Dictionary of English v.0.48:

Tarpon \Tar"pon\, n. (Zool.)
   Same as Tarpum.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Tarpum \Tar"pum\, n. (Zool.)
   A very large marine fish (Megapolis Atlanticus) of the
   Southern United States and the West Indies. It often becomes
   six or more feet in length, and has large silvery scales. The
   scales are a staple article of trade, and are used in
   fancywork. Called also tarpon, sabalo, savanilla,
   silverfish, and jewfish.
   [1913 Webster]

WordNet (r) 3.0 (2006):

tarpon
    n 1: large silvery game fish of warm Atlantic coastal waters
         especially off Florida [syn: tarpon, Tarpon atlanticus]