The Digital Fish Library

Distribution:
Atlantic, Indian and Pacific Oceans.

Habitat:
Reef-associated.

Remarks:
Triggerfishes are tetradontiform fishes with football-shaped bodies, leathery skin, plate-like scales, small mouths and powerful jaws. They are closely related to the filefishes of the family Monacanthidae, but are distinguished by having a more robust body and by having 3 (vs. only 2) dorsal spines.

Triggerfishes are known for their unique defensive adaptations. When threatened, these fishes erect the first dorsal spine, which locks into place. This prevents predators from swallowing the triggerfish or from prying it out of its crevice in the reef. The locked first dorsal spine is subsequently released by a trigger mechanism formed by the second dorsal spine. The name "triggerfish" refers to this locking and unlocking action of the first two dorsal spines.

All triggerfishes are capable of rotating their eyes independently. Some are capable of sound production, either by vibrating the gas bladder or grinding the teeth. They will grunt audibly when pulled out of water. Indeed, the Hawaiian triggerfishes Rhinecanthus aculeatus and R. rectangulus, are known commonly as humuhumu nukunuku apua'a, which translates to "the fish that sews with a needle and grunts like a pig."

Triggerfishes have strong jaws. The upper jaw has four teeth in the outer and three in the inner series on each premaxillary. Their mouths are developed for crushing hard-bodied prey such as mollusks and echinoderms, however some species feed on algae or zooplankton. These fishes also tend feed on prey animals that other predators avoid, including spiny sea urchins, venomous fireworms and the formidable crown-of-thorns starfishes of the genus Acanthaster.

Females lay eggs in a nest, usually a small hole dug in the ground. The female, and less often the male, aggressively guards the nest. These fishes are popular in the aquarium trade, but may be aggressive.

This family comprises 11 genera and about 40 species.

References:
Nelson 2006; Helfman et al. 1997; Allen & Robertson 1994; Thomson 2000