Our first group of familiar coral reef fishes are the butterfly fishes. Most of the butterfly fish are very colorful and live in close association with corals. All of the butterfly fish have a similar body shape, which is plate-like (thin, tall, and round). They are the opposite shape of a shark’s mouth, which illustrates how important a role predation has played in their evolution. Butterfly fish are the easiest fish to spot while conducting the EMP, and usually occur in pairs but sometimes can be found in schools.
Butterfly fishes are thin, tall, and plate-like to avoid predation. To further avoid predation, the tail of most butterfly fish looks just like the head, and often they have a line over their eye for disguise. Together these confuse predators, who don’t know which direction to sneak up on the fish, or which way the fish is going to swim to get away.
Butterfly fish feed on coral polyps, micro-invertebrates, and algae, so live only in healthy reef areas. In fact, graphs of coral abundance and butterfly fish abundance tend to be very closely correlated. In many areas they are a prized fish for the aquarium trade due to their bright colors, but on Koh Tao are mostly threatened by fishing activities or habitat destruction.