triggerfish, any of several species of tropical reef fishes with laterally compressed bodies, heavy scales, and tough skins. They are named for the mechanism of the three spines of the dorsal fin: when the fish is alarmed the first of these spines is locked upright by the second and drops only when the latter is pressed like a trigger. The function of this reaction is to lock the fish firmly in a mass of coral; when attacked, the fish dives into the coral and erects the spine, releasing it only when the danger has passed. Triggerfishes have powerful, chisellike teeth adapted for cracking the coral and mollusks on which they feed. They average 1 lb (0.45 kg) in weight and 1 ft (30 cm) in length and are common around the West Indies and Florida. The gray, or common, triggerfish is variably colored in mottled browns, yellows, or grays, but many other species are strikingly colored, e.g., the queen triggerfish in blue, green, and yellow. The ocean triggerfish, which unlike most triggerfishes found in waters away from reefs, among seaweed or debris; it is up to 2 ft (60 cm) long and may weigh as much as 13 lb (6 kg). Triggerfish are classified in the phylum Chordata, subphylum Vertebrata, class Actinopterygii, order Tetraodontiformes, family Balistidae.
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