The goatfishes are sometimes called 'red mullets' as opposed to the Mugilidae, the grey mullets, though that name is usually reserved for the red mullets of the genus Mullus of the Mediterranean. Within the family are six genera and about fifty-five species.
Description and habits
Many species of goatfishes are conspicuously coloured; however, they are not popular in aquaria. Rather, they are valued food fish in many countries. The largest species, the dash-and-dot goatfish (Parupeneus barberinus), grows to 55 cm in length; most species are less than half this size. Their bodies are deep and elongated, with forked tail fins and widely separated dorsal fins.
Perhaps their unpopularity among fishkeepers can be attributed to their feeding habits; goatfishes are tireless benthic feeders, using a pair of long chemosensory barbels ("whiskers") protruding from their chins to rifle through the sediments in search of a meal. Like goats, they seek anything edible; worms, crustaceans, molluscs and other small invertebrates are staples.
By day, many goatfishes will form large, inactive (nonfeeding) schools; these aggregates may contain both conspecifics and heterospecifics. For example, the yellowfin goatfish (Mulloidichthys vanicolensis) of the Red Sea and Hawaii is often seen congregating with bluestripe snappers (Lutjanus kasmira). With such mixed company, the yellowfins will actually change their coloration to match that of the snappers.
By night, the schools disperse and individual goatfish head their separate ways to loot the sands. Other nocturnal feeders will shadow the active goatfish, waiting patiently for any overlooked morsels. Goatfishes stay within the shallows, going no deeper than about 110 m. Some species, such as the freckled goatfish (Upeneus tragula) of East Africa, have been known to enter estuaries and rivers, although not to any great extent.
All goatfishes have the ability to change their coloration depending on their current activity. One notable example, the diurnal goldsaddle goatfish (Parupeneus cyclostomus) will change from a lemon-yellow to a pale cream whilst feeding. Diurnal species also tend to be solitary, but will school as juveniles.
Goatfishes are pelagic spawners; they release many buoyant eggs into the water which become part of the plankton. The eggs float freely with the currents until hatching. The postlarva floats in surface waters until it reaches around 5 or 6 cm in length, when it takes on the adult, bottom-feeding lifestyle.
In ancient Rome until the end of the second century AD, two species of goatfish (Mullus barbatus and Mullus surmuletus) were highly sought-after and expensive, not as a delicacy, but for aesthetic pleasure, since the fish assume a variety of colors and shades also during death. Therefore, it was paramount to serve the fish live and let them die before the eyes of the guests.