Trigger Fish

Triggerfish are about 40 species of often brightly coloured fish of the family Balistidae. They are often notoriously ill-tempered.

Triggerfish have an oval-shaped, highly compressed body. The head is large, terminating in a small but strong-jawed mouth with teeth adapted for crushing shells. The first spine is stout and by far the longest. All three are normally retracted into a groove. Characteristic of the order Tetraodontiformes, the anal and posterior dorsal fins are capable of undulating from side to side to provide slow movement and comprise their primary mode of propulsion.

As a protection against predators, triggerfish can erect the first two dorsal spines: The first (anterior) spine is locked in place by erection of the short second spine, and can be unlocked only by depressing the second, “trigger” spine, hence the family name “triggerfish”.

Some triggerfish species can be quite aggressive when guarding their eggs, viciously defending their nests against intruders, including scuba divers and snorkelers. Their territory extends in a cone from the nest toward the surface, so swimming upwards can put a diver further into the fishes' territory; a horizontal swim away from the nest site is best when confronted by an angry triggerfish.