The Collaborative International Dictionary of English v.0.48:

Sarpo \Sar"po\, n. [Corruption of Sp. sapo a toad.] (Zool.)
   A large toadfish of the Southern United States and the Gulf
   of Mexico (Batrachus tau, var. pardus).
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Toadfish \Toad"fish`\, n. (Zool.)
   (a) Any marine fish of the genus Batrachus, having a large,
       thick head and a wide mouth, and bearing some resemblance
       to a toad. The American species (Batrachus tau) is very
       common in shallow water. Called also oyster fish, and
       sapo.
   (b) The angler.
   (c) A swellfish.
       [1913 Webster]