Among the most colourful of the reef inhabitants is the Butterfly Fish family with their flat, thin bodies usually with a stripe through the eye and sometimes a dark blotch near the tail. This is their camouflage to confuse predators that mistakenly lunge for the wrong end of the fish. Butterfly fish can also actually swim backwards to escape danger. There are about 130 species which mostly inhabit coral reefs, many species live as mated pairs whilst others school in large numbers. A solitary travelling butterfly fish is in search of a soul mate, when the fish finally finds its mate they hunt, live and travel together for a life.
Here on Koh Tao we get copious amounts of the Eight-band-Butterflyfish - Chaetodon octofasciatus it grows to 12 cm in length and is one of the smallest of the family. It has a yellow to white body with eight black bands and has a black stripe along the top of the snout and a clear caudal fin margin. The adults usually live in pairs whereas the juveniles will congregate in groups.
We also have the Lined-Butterflyfish - Chaetodon linsolatus, which is one of the biggest butterfly fishes, reaching a maximum length of around 30 cm. It has a white body with vertical black lines and they have a black stripe on their head with a yellow and black tail. They are actually carnivorous and feed on smaller marine fishes, coral polyps, algae, small shrimp or zooplankton.
Another commonly seen Butterfly Fish here is the Weibels Butterfly fish - Chaetodon wiebeli and is also known as the Hongkong-Butterflyfish, growing up to 16cm. Its body is a beautiful bright yellow/ orange and the caudal fin is marked with a broad black band, offset by white in front. They can mostly be seen in pairs at most dive sites, though can also be seen in large schools at places such as Shark Island and Laem Thien. Definitely a favourite for the photo enthusiast....
The Copperband-Butterflyfish, more commonly known as the Beaked Coralfish - Chelmon rostratus, can also be seen now and again. This elegant looking fish grows up to 20cm and has a white body with wide copper and orange bands. They also have a black dot on the back of their body, which looks like an eye to entangle their predator. They have a long, narrow nose and mouth used for hunting into crevices and holes for food. They are more difficult to get a photo of but well worth the effort...
Finally the Pennant-Coralfish - Heniochus acuminatus, more commonly known as the Long fin Banner Fish is also actually part of the Butterfly fish family and is often mistaken for a Moorish idol. The fish is mostly black and white, with an elongated dorsal fin making the fish reach around 25 cm. The fish's caudal, anal and pectoral fins are most commonly bright yellow. They are a social fish, and are usually found in pairs or in shoals and are a perfect subject to photograph.
Butterfly fish swim by synchronized rowing strokes of their pectoral fins using the tail fin as a rudder for direction and balance. They are capable of very rapid movement and rely largely on their agility to avoid capture from other larger species.
Because of their food preferences Butterfly Fish only lives in healthy reef areas, so if there are lots of them it means it is a healthy coral reef. On Koh Tao the Butterfly Fish are mostly threatened by fishing activities, but in many other areas the Weibels butterfly fish in particular are prized fish for aquarium trade because of their beautiful bright colours.