Balistidae

Hairfin triggerfish

Abalistes filamentosus

Slender tail filaments trailing through dim deep water

• Tropical
• Regional distribution
• Marine fish
• Pacific Ocean
• Oceania
• Deep-bodied
• Compressed cross-section
• Medium
• Tropical fish

Distinguished by elegant trailing tail streamers, the hairfin triggerfish is an unusual balistid inhabiting the deeper continental shelf waters of the tropical Indo-West Pacific. Its oval, compressed body presents a dark brownish-black dorsal surface adorned with subtle pale blue dots and fine yellowish reticulations, while the cheek displays olive-green tints. The signature anatomical hallmark is its caudal fin, where the upper and lower lobes extend into delicate, prolonged filamentous streamers that flutter in deep currents. Three sturdy dorsal spines are housed in a specialized locking mechanism, allowing the first spine to lock erect for defense. Extending from the Ryukyu Islands of Japan through the Timor Sea to the Northwest Shelf of Australia and New Caledonia, it occupies deep sandy flats and rocky shelves between sixty-one and one hundred and eighty meters depth. A solitary benthic carnivore, it uses powerful chisel-like teeth to crack open sea urchins, bivalves, and crabs. Maximum recorded total length reaches thirty-two point five centimetres.

Sources: Australian Museum — Hairfin Triggerfish, Abalistes filamentosus