Many fish species do have tongues, although they are different than the muscular mammalian tongues that humans and many animals have. A fish tongue is essentially an extension of the base of the mouth, and some of the tongues even have small, sharp teeth to help the fish grasp prey.
Some species of fish with tongues end up losing the tongues to invading parasites. Several examples of this occur in various marine fish species. For example, several species of crustacean parasites take up residence in a fish's mouth and feed off the tongue until it is gone. At that point, the parasite then acts as a sort of pseudo-tongue for the fish and continues to feed off the fish's resources.