cutlass fish

 a peculiar, long, thin, marine fish (Trichiurus lepturus) of the southern United States and West Indies, having a long whiplike scaleless body and sharp daggerlike teeth; -- called also frostfish, saber fish, silver eel, and, improperly, swordfish; also, several related members of the genus Trichiurus. It is closely related to snake mackerel.  [1913 Webster]