Definition of pelican fish in US English:

pelican fish

noun

rare
  • An eel-like deep-sea fish, Eurypharynx pelecanoides (family Eurypharyngidae), having extremely large jaws with an enormous gape, thought to be kept permanently open while swimming in order to catch plankton or other organisms; also called gulper.

Origin

Late 19th century; earliest use found in Leisure Hour.