The Chevron Butterflyfish (Chaetodon trifascialis) is also known as the Triangulate Butterflyfish, V-lined Butterflyfish and Acropora Butterflyfish. In terms of their diet they are the most highly specialised of the butterflyfish, feeding exclusively on some species of acropora corals.
The body is oval and white with a chevron pattern across the body in black. The caudal fin is black with a yellow margin and a black bar lined with white runs through the eye. The dorsal and anal fins are a yellow orange colour. In juveniles as can be seen in the image below, the caudal fin is yellow and there is a black bar down the rear of the body.
At night the upper body darkens and two white blotches appear across the darkened patch. There is a small yellow line just above the mouth. They have a pointed snout with sharp, narrow teeth and grow to between 15-18 cm in length. It is impossible to sex them from their looks.
IN THE WILD
Chevron Butterflyfish are seen solitary and in pairs the wild and as with all butterflyfish are hard to approach closely. Although they swim in the open they always have a hole nearby to pop into and are quick to do so. If they think you are following them they hide. Being highly territorial the Chevron butterflyfish will chase members of their own species and other coral eating butterflyfish out of their territories.
They are found across the Indo Pacific area from the east coast of Africa to Hawaii, north to Japan and south to Australia. They will nearly always be around tabular and staghorn acropora corals.
Chevron Butterflyfish feed exclusively on the polyps and mucus of some species of acropora corals. Their status with the IUCN is “near threatened” because of potential habitat loss from global coral bleaching.
Typically a male will have a harem of two to three females whose territory overlap his. The female swells with eggs and spawning takes place by scattering into the water table with the male fertilizing the eggs. Spawning is thought to take place in relation to the lunar cycles. The eggs are spherical and buoyant and it is thought they hatch in 28 to 30 hours. Once the eggs hatch a bony plate forms over the head area of the larvae. The larvae called tholichthys, are pelagic for quite some time. They slowly develop into juveniles. This phase makes it extremely difficult to breed them in aquariums.
Chevron butterflyfish are not commonly kept in aquariums because of their specialized diet of acropora corals.