The Collaborative International Dictionary of English v.0.48:

Hairtail \Hair"tail`\ (-t[=a]l`), n. (Zool.)
   Any species of marine fishes of the genus Trichiurus; esp.,
   Trichiurus lepturus of Europe and America. They are long
   and like a band, with a slender, pointed tail. Called also
   bladefish.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Bladefish \Blade"fish`\, n. (Zool.)
   A long, thin, marine fish of Europe (Trichiurus lepturus);
   the ribbon fish.
   [1913 Webster]