This week in Lembongan… Generally speaking the titan trigger fish in Lembongan are not an issue, and on the odd occasions where a diver gets a nip on the fin, it is only just a nip and away swims the diver and away swims the trigger fish. We do not get the crazy stories or reactions from trigger fish like they do in places like Koh Tao, Thailand. But in saying that, we are still visitor to their environment and they need to protect their nest.
Trigger fish males migrate to their traditional spawning sites prior to mating and establish territories. Some male species build hollow nests within their territories. Trigger fish males are fierce in guarding their territories as having a territory is essential for reproduction. A male’s territory is used for spawning and parental care. Most male territories are located over a sandy sea bottom or on a rocky reef. A single territory usually includes more than one female, and the male mates with all of the females residing in or visiting his territory.
Trigger fish spawning is timed in relation to lunar cycles, tides, and time of changeover of tides. In relation to lunar cycles, eggs are observed 2–6 days before the full moon and 3–5 days before the new moon. In relation to tides, spawning happens 1–5 days before the spring tide. In relation to timing of tides, eggs are observed on days when high tides take place around sunset.
Male and female trigger fish perform certain pre-spawning behaviors: blowing and touching. A male and female blow water on the sandy bottom (usually in the same spot at the same time) and set up their egg site. They touch their abdomens on the bottom as if they are spawning. During actual spawning, eggs are laid on the sandy sea bottom. Eggs are scattered and attached to sand particles. Trigger fish eggs are usually very small (diameter of 0.5-0.6mm and are easily spread by waves. After spawning, both the male and female participate in caring for the fertilized eggs. A female trigger fish stays near the spawning ground, around 5 meters off the bottom, and guards the eggs within her territory against intruders.
Even in Lembongan where attacks from trigger fish are rare, it is still a good idea to be aware of the timing of trigger fish nesting as well as the area in which they nest. As more divers populate an area, the more we interrupt their nature and over time, this can result in them becoming more aggressive. A perfect example of this is in Koh Tao, Thailand.