Fusilliers
Scientific name Doryrhamphus
Fusiliers are fast-moving, streamlined schooling fish that bring constant motion and energy to Koh Tao’s dive sites. With slender torpedo-shaped bodies and vibrant blue and yellow colouring, they are usually seen moving in large, synchronised groups above reef slopes and pinnacles.
Species such as Caesio teres and Pterocaesio tile are common locally. Their forked tails and smooth, coordinated swimming allow them to handle moderate currents with ease. Schools often shift direction instantly, flashing silver-blue as they turn in unison.
Unlike many reef fish that stay close to coral, fusiliers spend much of their time in mid-water, feeding in the water column rather than directly off the reef. Their constant presence adds life to deeper dive sites, especially offshore pinnacles.
They are an important link in the reef food chain, acting as prey for larger predators such as trevally, barracuda and reef sharks. When fusilier schools tighten suddenly, it’s often a sign that a hunter is nearby.
Find Fusilliers at...
Divemaster's tip
Look into the blue water slightly above the reef between 10–30 metres. Fusiliers often hover in current-exposed areas.
If you notice the school suddenly compress or dart in a coordinated burst, scan the area — a predator may be passing through.
What do they eat?
Fusiliers primarily feed on zooplankton drifting in the current.
By filtering plankton from the water column, they convert microscopic life into energy that supports larger reef predators, making them a vital part of Koh Tao’s marine ecosystem.
