Blue Zoo: Titan Triggerfish
Featuring one amazing marine animal per week.
The titan triggerfish (Balistoides viridescens) is an extremely territorial fish that is native to Indo-Pacific lagoon and coral reef environments.
Like all triggerfish, this species is shaped a bit like a flattened football. The dorsal fin in these fish is reduced and consists of just three spines. Usually the spines remain flat against the body, but when pressure is applied to the second spine (the “trigger”), this locks the first spine into an upright position. At night, or when threatened, triggerfish can use this to lock themselves firmly and safely into crevasses in the coral reef.
Photo by BBM Explorer via flickr, Creative Commons License.
Triggerfish have a distinct way of swimming. Instead of using the tail, they use the large fins above and below the tail. The fins undulate, allowing the fish to swim slowly. They usually only use their tail when they need to quickly escape a predator.
The titan triggerfish is one of the largest species of triggerfish and can reach 75cm (30 inches) long. They tend to be greenish with dark edges, and their scales form a cross-hatched pattern.
They have a small mouth but their powerful jaws and strong teeth are useful for crushing hard-shelled prey, such as crabs, molluscs, or sea urchins. Often, smaller fish gather around a feeding triggerfish to feed on leftovers.
Photo by Janderk via Wikimedia Commons, Public Domain.
They are solitary animals and tend to spend their time either alone or with a mate, and they guard their territory against any intruders. Triggerfish usually make a nest in the sand on the seafloor and lay their eggs in the center of the crater. The female then guards the nest aggressively against predators and intruders.
Divers are wise to leave some distance between themselves and titan triggerfish or run the risk of being attacked. When guarding a nest, these fish have been known to inflict nasty bites upon those who venture too close.
Titan triggerfish are sometimes caught for food, although their meat has been linked to ciguatera poisoning. Their population status has not yet been evaluated by the IUCN.
Photo by nicoboxethai via flickr, Creative Commons License.
Primary source: Allen, G.R. and Erdmann, M.V. 2012. Reef fishes of the East Indies. Volumes I-III. Tropical Reef Research, Perth, Australia. Page 1059, 1061.