Triggerfish

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 (durophagy). Each jaw contains a row of four teeth on either side, while the upper jaw contains an additional set of six plate-like pharyngeal teeth. The eyes are small and set far back from the mouth, towards the top of the head. The gill plates (opercula), although present, are also not visible; they are overlaid by tough skin covered with rough, rhomboid scales that form a stout armor on their bodies. The only gill opening is a vertical slit, directly above the pectoral fins. Their small, restricted gill openings are a trait shared with other Tetraodontiformes.

The anatomy of the triggerfish reflects its typical diet of slow-moving, bottom-dwelling crustaceans, mollusks, sea urchins, and other echinoderms, generally creatures with protective shells and spines. Many also take small fishes and some feed on algae, such as the members of the genus Melichthys. A few, for example the redtoothed triggerfish (Odonus niger), mainly feed on plankton. They are known to exhibit a high level of intelligence for a fish, and have the ability to learn from previous experiences.

Off Florida, juveniles of some species of triggerfishes are found in floating Sargassum, where they feed on the small shrimp, crabs, and mollusks found there.

Triggerfish spawning is timed in relation to lunar cycles, tides, and time of changeover of tides. In relation to lunar cycles, eggs are observed 2–6 days before the full moon and 3–5 days before the new moon. In relation to tides, spawning happens 1–5 days before the spring tide. In relation to timing of tides, eggs are observed on days when high tides take place around sunset.

Some species of triggerfish, such as the titan triggerfish, may be ciguatoxic and should be avoided. Others, however, such as the grey triggerfish (Balistes capriscus), are edible.