The titan triggerfish, or Balistoides viridescens, inhabits the reefs of the tropical Indo-Pacific and Red Sea regions. Reaching a length of approximately 30 inches, it is the largest triggerfish species within its range. Typical in general form to most others in the Balistoides genus, the titan has large, protruding teeth in a relatively small but extremely powerful set of jaws that it is not hesitant to use when protecting its territory. Defense is the secondary purpose of the dentation, however; like most related species, the titan is an invertebrate feeder.
Although it will sometimes eat smaller fish, the titan triggerfish is not solely a piscivore. Instead, its primary diet consists of several species of echinoderms, crustaceans, mollusks, tube worms, and living coral. Even though they will devour soft-bodied animals such as tunicates, they are specialist feeders on hard-shelled organisms.
Several species of tube worms and branching corals, such as Acropora, are frequent targets; the titan triggerfish uses its powerful bite to break pieces off and crush them to extract the meat. They are often seen ‘grazing’ on the reef in just this way.
Their most common feeding technique, however, involves working the bottom, moving sand, rocks, and coral debris in a hunt for crabs and other crustaceans, as well as mollusks. All but the largest, thickest-shelled univalve or bivalve animals will be quickly crushed and eaten.
It is as an echinoderm hunter that the titan triggerfish is most noted. While individuals have been observed in the wild eating juvenile crown-of-thorns starfish, sea urchins seem to be the favored target, including the various long-spined, somewhat venomous Diadema species. The titan gets past their defenses by seizing the tips of the spines in its mouth and flipping the urchin upside down. This exposes the relatively unprotected underside of the urchin so the titan triggerfish can dig the meat out of the spiny shell.
The diet of the titan triggerfish makes its impact on the reef rather neutral, for while it feeds on the corals and tube worms of the reef itself, it also feeds on other reef predators and helps to keep their populations in check. Check out this fantastic video footage that shows the titan triggerfish hard at work getting its daily bread.
