Family-Animalia: Balistidae

Triggerfish are about 40 species of often brightly colored fish of the family Balistidae. Often marked by lines and spots, they inhabit tropical and subtropical oceans throughout the world, with the greatest species richness in the Indo-Pacific. Most are found in relatively shallow, coastal habitats, especially at coral reefs, but a few, such as the oceanic triggerfish (Canthidermis maculata), are pelagic. While several species from this family are popular in the marine aquarium trade, they are often notoriously ill-tempered.

Behavior

The rather bizarre anatomy of the triggerfishes reflects their typical diet of slow-moving, bottom dwelling crustaceans, mollusks, sea urchins and other echinoderms, generally creatures with protective shells and spines. Many will also take small fishes and some, notably the members of the genus Melichthys, feed on algae. 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.

Some triggerfish species can be quite aggressive when guarding their eggs. Both the picasso (Rhinecanthus aculeatus) and titan triggerfish (Balistoides viridescens) viciously defend 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. Unlike the relatively small picasso triggerfish, the titan triggerfish poses a serious threat to inattentive divers due to its large size and powerful teeth.

Reference: Wikipedia