It eats what nothing else can open. A sea urchin is turned over and attacked through the soft underside where the spines are short; coral branches are bitten off; thick-shelled molluscs are crushed. The tool is eight heavy incisors mounted on a short, powerful skull, and it is what lets a fish of 30 cm (12 in) make a living out of food that is armored against everything its size.
That jaw is also why it is one of the more aggressive animals on the reef for its size, and why the aggression is worth respecting. The nest is a shallow crater in sand or rubble, and the territory the female defends stands on it as a cone that widens toward the surface. Swimming up keeps you inside that cone the whole way, and swimming up and away puts you further in rather than further out. Leave sideways, stay low, keep the fish in sight, and put your fins between the two of you. She charges anything inside it and the bite takes chunks out of fins.
The fish itself is dark green, ruled with curved orange lines that run back from the snout across the whole body, with an orange band at the base of the tail and a yellow patch behind the mouth. Sexes are separable if you look at the snout: in females the orange lines cross it, in adult males they fade out before they get there. Very few triggerfish can be sexed in the water at all.
The genus. Balistapus Tilesius 1820 - a- (without) + pous (foot). ETYFish
The species. Balistapus undulatus (Park 1797) - wavy. ETYFish
- dark green body ruled with curved orange lines running back from the snout
- orange band across the base of the tail and a yellow patch behind the mouth
- males lose the orange lines across the snout, females keep them
- up to 30 cm
Why it's threatened
There are no known major threats.
Threat classification from the IUCN Red List.
