Butterflyfishes

Scientific name : Chaetodontidae

Amongst the more common and beautiful fishes on any reef. Called butterfly fish for the symmetry and the brilliant colours, they share with butterflies another feature: especially the coral feeders swim restlessly over the reef, "flying" and stopping shortly now and then to feed. A fleeing pyramid butterfly fish school recalls a swarm of butterflies. Normally easy to observe, because unwary of divers. Small fishes (max 30 cm), colorful, laterally compressed. Dorsal and anal fins are partially covered with scales, and have symmetric shape. The fish shape is triangular to trapezoidal, with pointed snout and small mouth. Heniochus species (banner fishes) have a filament on the anterior part of dorsal fin. Color pattern often with bands and spots, in the tones of white, yellow, orange, black. Very common a vertical band, concealing the eye. Common, especially in juveniles, a round spot ( false eye) in the back part of the fish, that could generate confusion in predators. In fact the false eye can prevent predators to foresee correctly the swimming direction of the butterfly fish; or, being larger than the true eye, can make the prey appear larger than real. Due to the spiny dorsal fin, they are not easy to handle and swallow. According some authors, the brilliant colours could be warning colour patterns. A precise signal for predators: I am here, but better not touch me! Butterfly fish mouth is small, snout more or less pointed. Teeth have the shape of a brush (this is the meaning of the word Chaetodontidae), good to feed on pieces of soft animals. The body is laterally compressed, good to swim between the coral branches in case of danger. Slow swimmers but with a very high capability to maneuver, butterfly fishes use caudal fin for propulsion, the highly mobile pectoral fins and the undulating dorsal and anal fins for narrow space maneuver. The maximum diversity of butterfly fish species is in the reef front. Most species are diurnal, and feed on algae, corals, worms and other small invertebrates. Few species feed on plankton and live in schools. Many species are territorial, many live in monogamic pairs, together for life, sharing a feeding territory. Floating eggs are abandoned in the current. The general body shape is similar to angel fishes (Pomacanthidae), and confusion is possible, especially with the smaller angel fish species. Butterfly fishes always lack the spine on the operculum, typical of angel fishes. Butterfly fishes are amongst the more conspicuous reef fishes. Some species feed exclusively on living hard corals. Those specie are considered coral reef's health indicator species.