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Home › Sea Life Facts › Marine Species › Vertebrates › Triggerfishes

Interesting Facts about Triggerfishes

[Triggerfish Phylum: Chordata] [Class: Actinopterygii] [Order: Tetraodontiformes] [Family: Balistidae]

These massive, brightly coloured marine fish are notorious for being able to lock the first spine of the dorsal fin by depressing the second shorter "trigger" spine. So what are they?

This section contains information about 40 species of triggerfishes (Balistidae), such as where they live, what they eat, and how they reproduce.

Trigger Fish Range and Preferred Habitats

The widespread distribution of triggerfishes (family Balistidae) occurs most in tropical and subtropical marine ecosystems.

However, the vast majority of the triggerfish species flourish in coral-rich hotspots around the world, such as:

• Atlantic Ocean (the Caribbean Sea, Gulf of Mexico, West Africa)
• Mediterranean Sea (and some temperate waters of the Atlantic)
• Indo-Pacific (Australia, East Africa, Hawaii, southern parts of Japan, and most of the Americas, including the Gulf of Mexico and Chile)

Still, they have a distinct preference for certain kinds of habitats. Besides being closely associated with coral reefs and reef flats, they also thrive in lagoons, around rocky coastlines, and in some seagrass beds or areas with algal-covered substrates.

Interesting Fact: Some of the less common species of triggerfish are pelagic, living offshore in open water, such as the ocean trigger fish (Canthidermis sufflamen) for example.

Triggerfish Behaviour and Characteristics

So, what are the key features that help trigger fishes stand out from most other examples of vertebrates fish that live in seas and oceans?

Most of them have a strong and laterally compressed build, with a somewhat oval appearance. Their skin is tough (almost leathery) and covered in small scales.

Some of the species have striking colouration. For example, the remarkable polka-dot and mosaic patterns of the bigspotted triggerfish (Balistoides conspicillum) create one of the most brightly coloured fish in the ocean.

But wait - there's more:

Triggerfish have very powerful jaw muscles and strong incisor-like front teeth. They use them to crush and crack open their favourite prey (hard-shelled invertebrates) and especially the crown-of-thorns starfish and sea urchins (echinoderms).

Their pectoral fins are quite small for a big fish. But, they have large dorsal and anal fins, mostly used for precise maneuverability and performing undulating motions.

It's fair to say that the average size of most species of triggerfish is about fifty (50) centimetres long (around 20 inches).

The stone triggerfish is the biggest in the species, often growing in excess of one (1) metre long (over 3 feet). By comparison, one of the smallest is the picasso triggerfish (rarely reaching more than 30 centimetres in total body length).

Dorsal Spines (Trigger Mechanism)

The first dorsal fin contains two, or sometimes three, stout spines. Triggerfish can lock the first spine in an upright position and then use the second spine in a "triggering mechanism" to unlock it - hence their funny scientific and common fish names of trigger fish and genus Balistes (crossbow fish).

By and large, they use the "trigger" as a defencive trait, such as by wedging themselves into reef crevices when they sleep.

Even so, triggerfishes rank among the most territorial of all reef fishes and aggressively defend their particular patch of reef - especially during their nesting season.

So, are triggerfish aggressive to humans... and what happens if a trigger fish bites you?

There are several ways to view triggerfish aggression, with a few potentially harmful consequences for scuba divers.

The least dangerous tends to be the nesting season aggression shown by females. They lay their eggs in a sandy patch close to coral reef formations and they fiercely guard them as the larvae develop.

Here's the thing:

Triggerfishes defend a cone-shaped patch that extends upwards and outwards into the water column. Hence, the "danger zone" is much bigger than the fish's relative size.

Generally, the fierce reputation that triggerfish have with scuba divers, and many less belligerent reef dwellers, is displayed by the males.

Male triggerfish will charge, chase, and bite anyone - or anything - that harasses them. In fact, not only can a bite damage your gear (especially diving fins), it can also break human skin and cause some serious laceration injuries and blood loss.

Territorial defence of this magnitude is not common around coexisting ecosystems. Yet, reef triggerfish will defend their own feeding and shelter sites against other reef fishes - including many of the biggest predators (e.g., grouper fish and some shark species).

The typical displays of threat include a raised dorsal spine (in the locked position), darkened body colouration, and sometimes a loud grunting noise (produced by their well-developed, gas-filled swim bladder).

Pro Tip: The wound from a triggerfish bite is usually quite painful, albeit rarely life-threatening! But, being bitten by a titan triggerfish increases the risk of ciguatera poisoning due to their venomous spines. As with most bleeding wounds, clean the wound with clean water and antiseptic, then apply a sterile bandage, and monitor the victim for signs of infection.

What Do Triggerfishes Eat?

Like many other powerful benthic feeders, the triggerfish anatomy has specialised into a marine ray-finned fish that is capable of crushing their primary diet, crustacean invertebrates (including crabs and shrimps).

Depending on the particular triggerfish classification, they are also known to supplement their diet by consuming:

• Algae
• Brittle stars (pictured)
• Clams
• Corals
• Mollusks
• Sand dollars
• Sea urchins
• Sea snails
• Sea sponges

Interesting Fact: Some fishkeeping hobbyists enjoy keeping triggerfish in aquariums as pets, even though they are not considered "reef safe" by most experts.

Types of Triggerfish Species

How Do Triggerfish Reproduce?

Having the reputation for being a confrontational fish species starts to become even more hostile during triggerfish reproduction strategies.

Like many marine vertebrates, spawning is oviparous, meaning trigger fish are egg layers. Even though some will gather in monogamous pairs to spawn, others may choose to have a single male guarding a nesting site occupied by multiple females.

Various courtship displays by a male usually involves some body colour changes, circling motions, and fin flaring to attract a female. Then, they dig into the sand or loose rubble near the reef to prepare a shallow pit.

Key points:

Female triggerfish are capable of depositing thousands of small sticky eggs inside the nest. The eggs stick together in small clusters either on the sand or attached to the rubble substrate.

Following that, she fans her fins to oxygenate the eggs and keep them clean. While she guards the embryos, the male's main role is defending the nesting territory against any unwanted intruders - and he will do so with fervent vigor!

It takes less than 48 hours for the eggs to hatch, which will be planktonic larvae that drift in open water for several weeks.

Some juvenile triggerfish will seek shelter (such as under floating Sargassum mats) until they are large enough to settle on the reef.

Fun Fact: The reproduction cycles of triggerfishes tend to occur during lunar cycles (e.g., new moon) and periods of warmer water, when planktonic food sources increase.

Threats and Predators

In fact, many triggerfish have an average lifespan of eight (8) years in the wild. Yet, the ones kept in aquariums as pets tend to live longer, often up to twenty (20) years - even though grey triggerfish (Balistes capriscus) are eaten by humans.

Although several factors pose a slight threat to the long term survival of some triggerfishes, they fulfill an essential role in keeping excessive numbers of crown of thorns (Acanthaster planci) and sea urchins (Echinoidea) at healthy levels.

Moreover, they face some significant threats from species of large predatory fish. The natural hunters of the trigger fish are:

• Groupers
• Sharks
• Snappers

Other contributing factors for the decline in a few vulnerable areas include certain types of human behaviour (e.g. coral reef destruction and degradation, overfishing, marine pollution, and excessive 'wild-catch' for the aquarium trade).

Pro Tip: According to a 2022 assessment issued by the IUCN Red List of Threatened Species, the conservation status of most triggerfish species is of "Least Concern" (LC). However, they list the queen triggerfish (Balistes vetula) as "Near Threatened" (NT).

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