Many divers and snorkelers who've explored Southeast Asia have a tale or two about the infamous Titan Triggerfish. Despite their fierce reputation, these fish are quite fascinating and beautiful. They're smart, playful, and a bit cheeky, making them a memorable part of any dive in Koh Tao!
Distinguishing Features
The Titan Triggerfish (Balistoides viridescens) is the largest triggerfish species in its range, reaching up to 75 centimeters in length. It has a robust, oval-shaped body covered with heavy scales. These scales are dark in the center, and the fish displays a distinctive black region with yellow spots around its eyes and extending to the bases of its pectoral fins. The dorsal and anal fins are pale yellow with black edges.
Its head is heavily scaled, with a deep groove in front of each eye and about five rows of spines on either side of its tail. Its strong jaws and teeth are specially adapted for crunching hard shells and corals, and dark markings above the mouth that resemble a mustache, making it stand out in the underwater crowd!
Behaviour, Feeding and Diet
The Titan Triggerfish is active during the day and prefers to live alone. It feeds on sea urchins, shellfish, crustaceans, tube worms, and coral. To find food, it flips over rocks, stirs up sand, and bites off pieces of coral. This behavior often attracts smaller fish that feed on the debris and tiny creatures stirred up. Titan Triggerfish can also hunt and eat crown-of-thorns starfish.
Reproduction
During mating season, Titan Triggerfish exhibit strong territorial behavior, with males performing intricate fin displays to attract females. Once a female selects a male, they collaborate to build a nest in the sand or coral, where the female lays up to several thousand eggs. The female then fiercely defends the nest, while the male patrols the surrounding area to protect their territory from intruders. After hatching, the larvae drift with the current before settling into the reef environment.
Defensive Behavior
The Titan Triggerfish is known for its aggressive defensive behavior, especially when guarding its territory or nesting sites. If threatened, it can become quite aggressive and may charge at intruders. Its strong jaws and sharp teeth make it capable of delivering painful bites. The fish often displays its large, colorful dorsal fin to appear more intimidating and may make quick, sudden movements to chase away potential threats.
Don’t mess with them when scuba diving
The titan triggerfish, though fascinating and beautiful, has a notorious reputation among divers. For most of the year, they're pretty chill, but during nesting season, they can get nasty. And by nasty, I mean really nasty! While they can't cause serious or life-threatening injuries, their large, sharp teeth are designed to crunch corals, and they pack a powerful bite that’s best avoided!
Usually the fish simply tries to escort the intruder out of its home, or adopts a defensive posture. Most of them are just protecting their nests, but some seem to enjoy snapping at divers' fins just for fun. Luckily, there are clear signs to watch for indicating that trouble might be on its way!
1. The "Trigger"
The titan triggerfish earns its name from its distinctive dorsal fin. Made up of three spines, when threatened, triggerfish can raise the first two spines, creating a sharp defense mechanism. The long first spine is held in place by the shorter second spine and can only be released by depressing the second 'trigger' spine, hence the name triggerfish. If you see the spine raised, it's a clear sign that the triggerfish is feeling threatened or anxious. This serves as a warning for divers to swim the other way to avoid any potential aggression.
2. The “Evil Eye”
When you catch the "evil eye" from their independently rotating eyeballs, it's time to steer clear! If their eyes are twitching or you see them rolling onto their side while glaring at you, it's a clear signal to retreat before they make a move. Keep an eye out for their raised black trigger fin, a sure sign of an impending attack!
Escaping Titan Triggerfish
If you find yourself face-to-face with a Titan Triggerfish that's taken a liking to your dive gear, don’t freak out! Start by positioning your fins between you and the fish to create a barrier. Often, the triggerfish is just trying to push you away from its territory, so better to protect your gear with your fins rather than risking a bite. Keep in mind that their territory is shaped like an upside-down cone around their eggs, so swimming straight up won’t help - Titan Triggerfish have been known to chase divers all the way to the surface. Instead, go horizontal and watch the fish closely as you make a quick, sideways escape. Once you’re out of their territory, they’ll stop chasing and return to their nest, leaving you with a thrilling story to share!
While the titan triggerfish's tough reputation isn’t totally off-base, remember they’re mainly just defending their territory and eggs. If you bump into one during nesting season, it’s smart to be extra cautious. Outside of that, they’re usually chill.
Your dive guide will give you a heads-up if you're near nesting areas - they know how to spot these spots and keep you safe. If you do encounter an aggressive triggerfish, you now know the warning signs and how to make a swift exit.
Where to Find the Titan Triggerfish on Koh Tao
You can spot Titan Triggerfish while scuba diving at several dive sites around Koh Tao! Look out for them nibbling on coral, crunching shells, and flipping over rocks at spots like:
