goatfish, also called surmullet, any of more than 60 species of elongated marine fishes of the family Mullidae (order Perciformes).
Goatfishes are characterized by two well-separated dorsal fins and by a pair of long, sensory chin barbels. The barbels are used to find the small, bottom-living invertebrates on which the fishes feed; when not in use, the barbels are held in a groove on the throat. Inhabitants of shallow water, goatfishes are found in warm and tropical regions, along reefs or over mud or sand. They are often brightly coloured, in shades of red and yellow; some are able to change their colours.
The largest goatfishes are about 60 cm (2 feet) long, but most are much smaller. Many species are edible and valued as food. One of the best known of these is the red surmullet, or red mullet (Mullus barbatus), of the Mediterranean, which was one of the most highly prized food fishes of the ancient Romans. Very similar is another European species, M. surmuletus.