Triggerfish

Triggerfish
Titan triggerfish (Balistoides viridescens)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Order:	Tetraodontiformes
Family:	Balistidae
Genera
See text.

Triggerfishes are brightly coloured fish of the family Balistidae.

Marked by lines and spots, they inhabit warm coastal waters of the Atlantic, Mediterranean and the Indo-Pacific.

Their size varies from 30 cm (1 foot) to 75 cm (2.5 feet). Most are solitary and diurnal. They feed on hard-shelled invertebrates, a few feed on large zooplankton or algae. They lay their demersal eggs in a small hole, dug in the ground. Some species guard their eggs.

Triggerfish have a roundish, laterally flat body with an anterior dorsal fin. They can erect the first two dorsal spines, the first one locks and the second one unlocks. This prevents predators from swallowing them or pulling them out of their holes. This locking and unlocking behaviour is why they are named 'triggerfish'.

They have a small pectoral fin, fused to one spine. Unlike the spine of a filefish, the spine of the triggerfish can be held in place by a second spine to make the fish more threatening to the predator. Their small eyes, situated on top of their large head, can be rotated independently. They have tough skin, covered with rough rhomboid-shaped scales that form a tough armour on their body. A big, angular-shaped head extends into a snout with strong jaws and sharp teeth, made for crushing shells. Each jaw contains a row of eight teeth, while the upper jaw contains another set of six plate-like teeth.

Some species of triggerfish are known to make a sound akin to a grunt or snarl when taken out of the water.

Behavior

A few of the triggerfish species can be quite aggressive during reproduction season. In particular Picasso triggerfish and titan triggerfish viciously defend their circular nests against any intruders, including scuba divers and snorkelers. Their territory extends in a cone shape from the nest to the surface, so swimming upwards puts you further into the fishes' territory. A horizontal swim away from the nest site is the most sensible course of action when confronted by an angry trigger fish. The Picasso triggerfish is relatively small, but due to its large size and powerful teeth the Titan triggerfish poses a serious threat to inattentative divers.

Picasso triggerfish (Rhinecanthus aculeatus)

Redtoothed triggerfish (Odonus niger) feeding on plankton

Titan triggerfish (Balistoides viridescens) with Orange-lined triggerfish (Balistapus undulatus) and moorish idols at the reef of Fihalhohi, Maldives

Orange-lined triggerfish (Balistapus undulatus)

Black triggerfish (Melichthys niger) and its reflection

Halfmoon triggerfish.

Genera

• Abalistes Bloch & Schneider, 1801
  • Abalistes stellaris : Starry triggerfish
• Balistapus Tilesius, 1820
  • Balistapus undulatus : Orange-lined triggerfish
• Balistes Linnaeus, 1758
  • Balistes capriscus: Grey triggerfish
  • Balistes ellioti
  • Balistes polylepis : finescale triggerfish
  • Balistes punctatus : Bluespotted triggerfish
  • Balistes rotundatus
  • Balistes vetula : Queen triggerfish
  • Balistes willughbeii
• Balistoides Fraser-Brunner, 1935
  • Balistoides conspicillum : Clown triggerfish
  • Balistoides viridescens  : Titan triggerfish, mustache triggerfish
• Canthidermis Swainson, 1839
  • Canthidermis maculata: Spotted oceanic triggerfish
  • Canthidermis macrolepis : Large-scale triggerfish
  • Canthidermis sufflamen : Ocean triggerfish
• Melichthys Swainson, 1839
  • Melichthys indicus : Indian triggerfish
  • Melichthys niger : Black triggerfish
  • Melichthys vidua : Pinktail triggerfish
• Odonus Gistel, 1848
  • Odonus niger : Redtoothed triggerfish
• Pseudobalistes Bleeker, 1865
  • Pseudobalistes flavomarginatus Yellowmargin triggerfish
  • Pseudobalistes fuscus : Blue or rippled triggerfish, blue-and-gold triggerfish, yellowspotted triggerfish
  • Pseudobalistes naufragium : Stone triggerfish
• Rhinecanthus Swainson, 1839
  • Rhinecanthus abyssus
  • Rhinecanthus aculeatus Picasso triggerfish, Lagoon triggerfish (USA)
  • Rhinecanthus assasi : Arabian picasso triggerfish
  • Rhinecanthus cinereus
  • Rhinecanthus lunula : Halfmoon picassofish
  • Rhinecanthus rectangulus: Reef triggerfish, Humuhumu-nukunuku-a-pua'a (Hawaii)
  • Rhinecanthus verrucosus : Blackbelly triggerfish
• Sufflamen Jordan, 1916
  • Sufflamen albicaudatum : Bluethroat triggerfish
  • Sufflamen bursa : Boomerang triggerfish
  • Sufflamen chrysopterum : Halfmoon triggerfish
  • Sufflamen fraenatum : Masked triggerfish
  • Sufflamen verres : Orangeside triggerfish
• Xanthichthys Kaup in Richardson, 1856
  • Xanthichthys auromarginatus : Gilded triggerfish
  • Xanthichthys caeruleolineatus : Bluelined triggerfish
  • Xanthichthys lineopunctatus : Striped triggerfish
  • Xanthichthys mento : Redtail triggerfish
  • Xanthichthys ringens : Sargassum triggerfish
• Xenobalistes Matsuura, 1981
  • Xenobalistes punctatus : Outrigger triggerfish
  • Xenobalistes tumidipectoris

References

• Froese, Rainer, and Daniel Pauly, eds. (2005). "Balistidae" in FishBase. December 2005 version.