Triggerfish are in the family Balistidae and there are about 40 different species. They are found in the tropical and subtropical oceans across the world with the greatest number in the Indo-Pacific.
Triggerfish obtain their name from the mechanism that locks their first dorsal spine in place. Once erected , the second dorsal spine locks into the lower part of the first spine preventing it from lowering. This second spine is known as the trigger. The spines are used to lock the fish into crevices when they are threatened by predators.
Triggerfish have a laterally compressed body with the eyes set up high on the body and far back from the mouth. The eyes are capable of independant movement. They have powerfull jaw muscles with strong sharp teeth that are used for crushing shellfish, crustaceans and urchins.Their skin is thick and tough and provides protection against predators as well as parasites and they are very hardy fish.
They mainly swim using their soft rear dorsal and anal fins and only use the caudal fin for an extra burst of speed when necessary. Often they will enter crevices sideways to escape potential predators.
Females lay their eggs in patches in the sand and aggessively defend the area. Some such as the Titan Triggerfish Balistoides viridescens can be dangerous to divers as they can inflict painfull wounds.
When confronted with a defensive trigger fish it is best to swim away from it horizontally in the opposite direction from that in which it is coming. On occasion a particularly aggressive fish may follow a diver for some distance attempting to nip the diver on his extremities. Perhaps the best tactic is to swim backwards away from the fish presenting ones fins for biting rather than any body part. Some divers resort to taking off a fin and waving it at the fish to chase it away when they persist after one has left the immediate area.
Only the smaller species are generally kept in home aquariums and care has to be taken when choosing them and their tank mates.