Latin name

Balistoides viridescens

Other names

Giant triggerfish, moustache triggerfish.

Identification

They get their name from the fixation mechanism used to hold the dorsal spine in place. The main dorsal spine is held in an upright position by a second spinal column, which fixes the dorsal spine in place.

The body has a typical Balistidae shape, with the eyes set high on the body and far from the mouth. This protects the eyes when feeding on sea urchins and some crustaceans. There is a deep notch in front of the eye; an area without scales around the lips, continuing and tapering backwards from the corner of the mouth; small, forward curved spines in about five rows on the sides and a short distance in front of the caudal peduncle. The caudal peduncle is compressed. The skin is thick and leathery, partly for defence against spiny prey. These fish have a small mouth with strong, large teeth. 

Features of fish fins

Dorsal spines: 3; dorsal soft rays: 24-26; anal spines: 0; anal soft rays: 22-24.

Fish colouring

The body is brownish with brown-orange lines running down the body in a diamond pattern. There is a dark brown patch above the mouth and another dark brown patch runs down the centre of the face to the eyes and then down to the pectoral fins. The area under the mouth is whitish. The eyes are convex and surrounded by a white ring with thin brown lines. The tail is whitish and the caudal fin is pale yellow with a brown band in front and behind. The dorsal fins are yellow-orange with a brown edge.

Distribution

They live in the Red Sea and the Indo-Pacific from the coast of South Africa to Japan, the Line Islands, Tuamotu and New Caledonia.

Habitat

Occupies lagoons, seaward reefs and sheltered slopes of inner reefs. Juveniles are often associated with isolated patches of branching coral or fragments of shallow sandy shelters.

Size

It is about 75 centimetres long and weighs 10 kilograms.

Behavior

Adults are found alone or in pairs.

The fish is capable of turning large blocks of stone with its strong chin to retrieve hidden prey. They're  very vigorous in defending their territory from uninvited guests. This behaviour is typical of the fish in the period after they have finished building their nests, which can reach a diameter of almost 2 metres and a depth of 75 centimetres.

Food and feeding habits

Their diet consists of madrepore corals, especially branching and spiny species of the genera Acropora and Pocillopora, which they break off with their powerful jaws, as well as starfish, sea urchins (Diadematidae), snails, polychaete worms, bivalves, algae and detritus. Prey lurking in the sand is extracted from the mouth with a powerful jet of water.

Reproduction

Reproduction  takes place between a male and a female. Females lay eggs on the substrate and the male fertilises them. The female then guards the eggs so that they are not eaten by predators. While the female is guarding the eggs, her behaviour can be very aggressive.

Fishing

Considered very tasty to eat, they are hunted by fishermen in some areas.

Relationship with a person

Eating this fish can lead to poisoning from ciguatoxin, which is found in the fish's tissue. 

Often hostile to divers and may attack unprovoked when tending eggs.