The family Chaetodontidae, known commonly as the butterflyfishes, consists of approximately 120 species and 10 genera; although, the number of genera varies from one classification scheme to the next.  The majority of these species occur in relatively shallow water around coral reefs.  Some butterflyfishes (e.g., Carribean Longnosed, Bank's Burgess, Marquesan and Tinker's butterflyfishes) are most abundant in deep water (30 m, 100 ft).  There are also species that occur in warm temperate or subtropical waters around rocky reefs.  For example, the Truncate butterflyfishes is found in the cool waters of South Australia.

 Most butterflyfish feed during the day, mate at dusk and sleep in reef crevices at night. The Raccoon butterflyfish is an exception; it is nocturnally active, feeding on nudibranchs, spaghetti worm and tube worm feeding tentacles, anemones, small crustaceans and other benthic invertebrates.

The color patterns of most butterflyfishes include eye mask and many also have false eyespots (ocelli) on the posterior part of their bodies.  This color pattern may deflect the attack of a predator away from the vulnerable head, toward the tail, giving the butterflyfish a greater chance of survival.  The bright, conspicuous colors of butterflyfishes may also serve an aposematic (warning) function.  Their deep bodies and long dorsal and anal spines make them unpalatable to most piscivores and their color may alert predators of this fact.  Butterflyfishes have been observed "mobbing" potential predators, like moray eels.

Studies suggest that all the butterflyfishes are gonochoristic, that is they do not change sex.  Many species occur in heterosexual pairs that move over a large home range or defend a territory.  A few species occur singly, for example, the solitary Chevroned butterflyfish vigorously defends a small territory (usually the top of a table coral) from other butterflyfishes.  Those butterflyfish species that feed on zooplankton, like the Pyramid butterflyfish and Schooling bannerfish (Heniochus diphreutes), often form large schools.

The diet of butterflyfishes consist primarily of benthic invertebrates. Some butterflyfishes are extremely specialized feeders; for example, some species feed exclusively on stony coral polyps.  This group includes Bennett's, Ornate, Meyer's, Reticulated, Chevroned, and Red-fin butterflyfishes.  At least one of these, the Ornate butterflyfish, feeds more on hard coral mucus than on the polyps themselves.  There are other butterflyfishes that are facultative coral feeders, that is , they feed on hard coral polyps to varying degrees.  This group includes the Threadfin, Four-eye, Saddled, Raccoon, Pelewensis, Four-spot, Double-saddled, Teardrop and Vagabond butterflyfishes and the Pennant and Masked bannerfishes.  These butterflyfishes also feed on algae, sponges, soft corals, anemones, tube worm tentacles, peanut worms, nudibranches, small crustaceans and ascidians.

There are also butterflyfishes that do not feed on coral at all, at least in certain parts of their geographical ranges. In Japan the Highfin coral fish feeds exclusively on ascidians, sponges and hydroids.  Members of the genus Chelmon, Chelmonops, Forcipiger and the subgenus Prognathodes (i.e., Atlantic Long-nosed, Bank's Scythe, and Brazilian Long-nosed butterflyfishes) have greatly exaggerated snouts that allow them to feed on noncoralline invertabrates hiding between coral branches or in reef crevices.  Although similar in appearance, the two members of the Forcipiger show significant differences in their jaw morphology and feeding behavior.  Forcipiger flavissimus has jaws that are like needle-nosed pliers that allow it to rip the tube feet and pedicellaria off sea urchins and the feeding tentacles off tube worms. The snout of the Big Long-nosed butterflyfish is more like a pipette that is used to suck up small crustaceans.  There are also a number of butterflyfish species that feed on zooplankton.  This includes Klein's (in some areas) and the Pyramid butterflyfishes and the Schooling bannerfish.  The Barber fish, the Schooling and Longfin bannerfishes also act as cleaners, picking external parasites off other fishes.

Articl by Scott Michael