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Witness the impressive Trigger Fish on the reefs near Port Douglas

Certain species of trigger fish can be the most annoying fish for divers upon the Reef.

The trigger fish family is named for a set of spines the fish uses to deter predators or to trap itself into holes, crevices and other hiding spots. The first spine is locked in place by the erection of a shorter second spine. It can only be unlocked by depressing the second, or the “trigger” spine.

They possess a strong set of teeth as they generally feed upon sea urchins, or dig out prey like crabs from the sandy bottom. To access these bottom dwellers, they flap debris away with their fins and squirt water from their mouths to scatter the sand. Smaller fish often follow trigger fish to feed upon their leftovers.

There are about 40 different species of trigger fish, and generally only one divers need be wary of. During the mating season, trigger fish will guard the nest, which sits in a flat, sandy area. The female stays close, blowing water on the eggs to provide oxygen to the embryo. The male stays farther above the eggs, guarding the female and eggs from intruders, like goat fish and moorish idols, and perceived intruders, such as divers.

The frequently seen titan trigger fish, Balistoides viridescens, is an aggressive bodyguard. You can determine when they feel threatened due to their posture. It will face the intruder with the first dorsal spine erect. It may roll onto it’s side, their independently rotating eyes watching you to get a better look. If it perceives you as a threat, it will swim towards you trying to bite you or your fins, as it escorts you out of their territory. The territory they defend extends in a cone shape, from the nest to the water’s surface. If you swim upwards to avoid this fish, you are actually swimming further and further into their territory. Stay low and swim horizontally away from the nest to avoid this aggressive protector. (You have been warned!)


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