The fish with the longest common name on this list is the state fish of Hawai'i. The Humuhumunukunukuāpuaʻa, also known as the reef triggerfish (Rhinecanthus rectangulus), inhabits coral reefs and sandy bottoms in warm waters of the Pacific, Indian Ocean, and southeast Atlantic. Hawai'i is near the eastern edge of this species’ native range.

The lagoon triggerfish (Rhinecanthus aculeatus) is also called humuhumunukunukuāpuaʻa and is a sister species to the reef triggerfish. However, the reef triggerfish—the official state fish Hawai'i—should not be confused with the lagoon triggerfish. The reef triggerfish shows more yellow coloration than its close relative. Coral reef fish in general are well known for their dazzling display of colors, which can serve important roles in communication, mate attraction, and threat displays.

Reef triggerfish eat a wide range of invertebrates and algae. Their diet includes echinoderms like sea urchins and brittlestars, marine worms, crabs, snails, and the algae that grows on corals and rocks. Algae are a triggerfish favorite. Triggerfish, and other members of the order Tetradontiformes such as pufferfish and filefish, have more developed jaw muscles than most fishes. This allows them to bite and chew their prey instead of sucking it up like a vacuum, which is the feeding method used by many other fish.

This unusual anatomy appears to extend internally as well. A recent study of the reef triggerfish brain found that it possesses a long cerebellum. In humans, the cerebellum sits beneath the cerebral lobes at the back of the brain, near the top of the spinal cord. In the reef triggerfish, however, the cerebellum is the largest structure in the entire brain. The cerebellum is typically one of the smaller structures in vertebrate brains, humans included.

Reef triggerfish feed during the day and at night they retreat into crevices in the coral for protection. There, they rely on bony structures that give the triggerfish their name: strong dorsal spines that can be raised and locked firmly into place. These spines anchor the body so securely that a predator cannot pull it out.

Triggerfish have a different mode of swimming than most other fishes. Most fish propel themselves by sweeping their tail fin—and much of their body—side to side. However, the reef triggerfish relies primarily on the fins along its body instead, using its anal, dorsal, and pectoral fins. This style of swimming provides greater maneuverability and is especially useful for navigating the tight spaces of coral reef. It can even move backwards.

When threatened or stressed, reef triggerfish are noisy. They produce sounds described as a hum or a drum by rubbing their pectoral fins against bony scutes, similar to scales, on their body. This sound is then amplified as it resonates off the swim bladder that sits beneath the scutes. Highly territorial, reef triggerfish do not limit their aggression to other fish. They are known to confront much larger intruders as well, charging at and even biting divers who wander too close to their nests.

The reef triggerfish holds cultural significance to native Hawaiians. In Hawaiian mythology, it is associated with Kamapua'a, a demigod who could take many forms, including that of a fish. In Hawaiian aquaculture, triggerfish were also placed into loko i'a, or traditional Hawaiian fishponds, as a biological management tool. By feeding on algae and invertebrates, they helped keep pond ecosystems balanced and productive.

References and Further Reading

Bowie Coffey, BN. 2020. Context-specific sound production responses to environmental manipulation in the vocal reef fish Rhinecanthus rectangulus. University of Hawai'i at Mānoa.

Champ, C.M., Vorobyev, M. and Marshall, N.J., 2016. Colour thresholds in a coral reef fish. Royal Society Open Science 3(9): 160399.

Friel, JP, and PC Wainwright. 1999. Evolution of complexity in motor patterns and jaw musculature of tetraodontiform fishes. The Journal of Experimental Biology, 202: 867-80.

Johnson M. 2021. Creature of the month holidays 2020: reef triggerfish. Accessed 12/30/2025. https://manoa.hawaii.edu/mop/2021/01/02/creature-of-the-month-holidays-2020/.

Maui Ocean Center. nd. Reef triggerfish. Accessed 12/30/2025. https://mauioceancenter.com/marine-life/reef-triggerfish/.

Raick, X, D Lecchini, L Kéver, O Colleye, F Bertucci, and É Parmentier. 2018. Sound production mechanism in triggerfish (Balistidae): a synapomorphy. Journal of Experimental Biology, 221: jeb168948.

Waikiki Aquarium. nd. Reef Triggerfish. Accessed 12/19/2025. https://www.waikikiaquarium.org/experience/animal-guide/fishes/triggerfishes/reef-riggerfish/.