Butterflyfish belong in the Actinopterygii Class like most fish, and the Family Chaetodontidae. The name Butterflyfish may reference the wide variety of colors and patterns they come in, as well as the occasional spot near the tail end of the fish resembling an eye. Like actual butterflies, this fake eye serves as a way to confuse potential predators. Scientifically speaking, these fish are named after their spectral comb-like teeth. The Family name Chaetonidae is a combination of the greek words for “teeth” and “comb.”
Their comb-like teeth and sharp protruding mouths allow butterflyfish to graze on tougher substances and look for food in small crevices. They may be generalists with a diet consisting of small invertebrates, fish eggs, polychaete worms, algae, and coral, or specialists. The Barberfish even cleans off parasites from other fish such as sharks and rays. About a quarter of all butterflyfish species are corallivores who feed only on coral. Only around 41 fish species feed directly on coral as a primary source of nutrition, but 60% of these fish are butterflyfish. Coral reefs are the primary habitat of most butterflyfish, but some do inhabit deeper waters.
Butterflyfish can be found in tropical to warm temperate waters in the Indo-West Pacific and from Australia to Taiwan. There’s only a handful found in the eastern Pacific and Atlantic. There are over 130 different species of butterflyfish. One of the newest species recently discovered and named in 2016 was the Basabe’s butterfly fish, found 180 feet off the north-western Hawaiian Islands. Butterflyfish may be found in pairs or in aggregations in the hundreds. Many of the corrallivore butterflyfish are monogamous. Butterflyfish do communicate with one another through sounds, either to ward off members of the same species, or to add their other half. They are also the most likely fish to breed with different species of butterflyfish.
Butterflyfish are a very popular specimen for both divers and aquarium enthusiasts. In the aquarium trade, the most expensive butterflyfish to purchase is the rare deepwater Wrought Iron Butterflyfish for $3800. Butterflyfish fish with a generalist diet or who feed off of plankton are manageable in aquariums, but those that strictly feed off of coral and sea anemones are very difficult keep alive.
These fish are pelagic spawners with a very unique tholichthys larval stage in their development cycle; Bony armor covers their head during this stage. Eventually, the bony plates become absorbed, so it’s never visible in juvenile or adult butterflyfish.
At the moment, there are only five species of butterflyfish listed as vulnerable to extinction. The major threat is any human activity that may destroy the limited habitat of butterflyfish, such as the coral reef beds they live off. Butterflyfish are a good indicator species as to the health of a coral reef bed because they need plenty of healthy coral to feed off of. A lack of butterflyfish could mean there’s too much coral that is either sick or dead.