Titan Triggerfish Will Seriously Mess You Up

The PADI textbook may be rife with information about avoiding the bends, nitrogen narcosis, and rip tides; but it’s relatively silent on dangerous sea creatures.  It offers some perfunctory advice, most of which boils down to “no touching,” yet never mentions which species, exactly, pose threats.  Some animals, like sharks, stingrays, and moray eels, everybody knows to regard with caution.

Others, such as titan triggerfish, don’t seem treacherous until they’re pummeling your face with their teeth.

Triggerfish are simply too goofy to be intimidating. In identification guides, the world’s forty species of triggerfish fall into the ignominious category “Oddly-Shaped Swimmers,” which has to be a little embarrassing if you’re a fish.  Triggers are endowed with huge bulging heads, independently rotating eyes that protrude like marbles, and tiny undulating fins that appear far too small to propel their decidedly un-aerodynamic bodies.  To their credit, triggerfish also have a cool eponymous adaptation: to protect against predators they can raise two dorsal spines, which when locked into place resemble a trigger.  The spines are usually engaged at night.  They still look weird during the day.

An orange-lined triggerfish - a common sighting at Mabul and Sipadan Islands - with dorsal trigger fully engaged. Courtesy of animal-world.com.

Despite triggerfish’s benign appearance, our certifying instructor, a normally insouciant Dutchman named Jesse, warned us about them vehemently before we got in the water.  “Ya, ya, they are dangerous,” Jesse told us with uncharacteristic gravity, stabbing at the fish ID book with an index finger.  He was pointing at one species of triggerfish in particular: the titan trigger (Balistoides viridescens if you speak Latin), one of the largest types in the world.

Being an Oddly-Shaped Swimmer probably got this titan triggerfish made fun of on the playground. (Can't believe I just resisted a "school" pun.) Titan triggers are found throughout Indo-Pacific waters; we saw them frequently in Thailand and Malaysia. Image courtesy of aquaviews.com.

“The triggerfish, she has a nest,” Jesse explained. On a whiteboard he drew a pile of rocks on the seafloor meant to represent the nest.  “She stays near her nest all the time.  And she has a territory around her nest,” he went on, drawing as he spoke, “shaped like this.”

He drew back from the whiteboard to reveal an inverted cone, a funnel, rising from the rockpile.

“You go into her territory…” He shook his head, and pounded a fist – presumably the female triggerfish – into his open palm – presumably a diver’s face.

Titan triggers are capable of delivering a nasty bite. The internet disagrees about whether the bite of the triggerfish is toxic. Eating triggerfish flesh, like the flesh of many reef fish, sometimes causes ciguatera in humans, an illness produced by dinoflagellates in the fish's diets. Whether the bite is ciguatoxic, however, is up for dispute. Image courtesy of patmillerphoto.com.

Titan triggerfish, he explained, respond more aggressively to potential predators during mating season: which, being April at the time, it was.  A nasty bite on the arm, a chomp on the rubber fin, and a couple of angry charges had sent several trespassing divers packing in recent days.  (In the future, I was to hear even more tales of triggerfish assaults, including a shattered mask and a cut on the forehead requiring three stitches.)  Titan triggers are not small fish – some are nearly a meter long – and despite being Oddly-Shaped Swimmers they can build up some pretty serious momentum. Not only are they powerful, they’re highly intelligent, and capable of learning from previous experience – if a triggerfish discovers that it can ward off divers by sinking its teeth into arm-flesh, it’s liable to try that tactic again.

For reasons that are not totally understood, titan triggerfish defend a funnel-shaped territory that widens as it rises*.  This means that a diver’s natural reaction to danger – ascension – actually keeps them squarely in the trigger’s defense zone.  An aggrieved triggerfish will keep chasing a frantically rising diver right to the surface, and presumably onto the boat if it could.  The proper response to a triggerfish attack, then, is to swim horizontally and toward the bottom, with fins splayed out to ward the fish off.  Good luck remembering the proper response when you’re being targeted by an enraged yellow missile.

*All species of triggerfish build nests, and most have cone-shaped territories; but only two species- the titan and picasso triggerfish – defend their turf violently. Not coincidentally, these are also the two species big enough to inflict actual damage.

***

We hit the water that first day with some trigger-related anxiety.  Jesse had warned us that an especially large titan trigger made her home nearby, and that if we saw her we were to cower behind him like the pansies we were.  Screw that, I thought: I’m provoking an attack.  The resultant scar would be a cool synecdoche for a great story.

But when the trigger appeared I obeyed Jesse and ducked.  The triggerfish fluttered awkwardly in a vertical position, facing downward, pecking at the sand even as its body tugged surface-ward like a helium balloon.  Was it arranging its legendary nest?  Hunting for crustaceans and echinoderms, its preferred food?  We were triggerfish neophytes, and there was no telling.

A titan triggerfish feeds on something crunchy and delicious (an echinoderm, crustracean or mollusk). Image courtesy of flickriver.com.

We watched the trigger until it drifted off into the poor visibility, and then went on our way.  I’ve encountered many triggerfish since then, and even violated their holy funnels, but no trigger has ever shown the slightest peevishness.  Yet during each interaction I feel the same thrill of unease – there’s something discomforting about the discrepancy between the fish’s inelegant body plan and the menace it poses; it’s like a corpulent cinematic gangster.  I’ll probably end many posts this way, but: they’re wonderful fish.