Bannerfish
bannerfish
Threeband pennantfish
Heniochus chrysostomus
About
The threeband pennantfish is a small butterflyfish of coral-rich reefs across the Indo-Pacific. Its body is white with three wide dark bands, and the front of its dorsal fin is drawn out into a long banner, which is where the name comes from. It reaches 18 cm. It feeds mainly on coral polyps, the tiny soft animals that build the reef. Adults are usually seen in pairs; young fish are on their own.
Also known as: horned coralfish, pennant bannerfish, threeband pennant, threeband pennantfish, horned coralfish, three-banded bullfish, threeband pennantfish, pennant bannerfish, threeband pennant, three-banded bullfish
- Length
- 18 cm
- Depth
- up to 40 m
How to tell it apart
Use the middle band's position as the fixed check: it runs from the front of the dorsal fin back to the rear of the anal fin. That placement stays the same on every fish, while the trailing dorsal pennant can look shorter, folded, or worn down depending on the individual.
Appearance
The body is disc-shaped and strongly flattened from side to side, so the fish looks tall and thin. The ground colour is white, cut by three broad, slanting dark brown bands: the first runs from the top of the head down through the eye to the belly, the second slopes from the front of the dorsal fin back to the rear of the anal fin, and the third lies across the back and the dorsal fin behind it. The first rays of the dorsal fin are stretched out into a black and white pennant. The snout is short with a small mouth that can be pushed forward, and there is a yellow mark on the mouth, over the top of the snout and running between the eyes. The rear of the dorsal fin, the tail and the pectoral fins are orange-yellow. Young fish carry a black spot ringed in orange-yellow low on the anal fin, and their pennant is longer and narrower than an adult's.
Habitat
It is widespread through the tropical and subtropical central Indo-Pacific, from the west coast of India east to Polynesia and from southern Japan south to New Caledonia. It sticks to coral-rich ground: shallow reef flats just below the tide line, lagoons and seaward reefs, from 2 m down to 40 m. Young fish live somewhere softer, in lagoons and estuaries, where river water mixes with the sea.
Log it in Into the Blue
Describe what you saw and we name it, then keep every species you find in your Oceandex.
