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Conservation Status:  Safe for Now

AquaticWedge-tail Triggerfish

Rhinecanthus rectangulus Bony Fishes

Aquarium of the Pacific - Online Learning Center - Species Print Sheet

Wedge-tail Triggerfish
Humu humu nuku nuku apua ‘a, the fish with the pig-nosed face | Oyd under Creative Commons Attribution 2.5
Wedge-tail Triggerfish
Humu humu nuku nuku apua ‘a, the fish with the pig-nosed face | Oyd under Creative Commons Attribution 2.5

Species Overview

The official state fish of Hawaii, the easily identified wedge-tail triggerfish is quite commonly seen in many other areas of its distribution. Besides its beautifully bright colors and perfect geometric markings, its greatest claim to fame is probably its official Hawaiian name, humu humu nuku nuku apua ‘a, which, according to Hawaiians, is longer than the fish itself. Not easy to learn and difficult to remember, it is said that native Hawaiians identify non-islanders by asking them to say the name. If not readily forthcoming, it leaves the persons background in question. Translation of the name to English defines the animal as the “fish with the pig-nosed face”. It is supported by the grunting noise the species may make when removed from the water.

Species In-Depth | Print full entry

At the Aquarium

This species Aquarium habitat is in the Tropical Pacific Gallery’s Lionfish and Triggerfish Exhibit.

Geographic Distribution

South Africa, Madagascar and associated islands, the Red Sea, Indonesia, Australia, southern Japan, and south to Lord Howe Island, and the Marquesas. Common in the Hawaiian Islands chain.

Habitat

These fish prefer outer reef locations where the water is often very active, with bottoms of reef rubble such as broken coral and rock structures to depths of about 20 m (65.6 ft).

Physical Characteristics

This fish has the roughly ovoid shape typical of triggerfishes in general. It is laterally compressed, but has a robust build. Its eyes are set far back and near the top of the head and can be independently rotated. The head tapers forward, ending in a small, terminal mouth containing small but sharp, sturdy teeth designed for crushing small, hard shelled animals. Each jaw has a row of eight teeth, and the upper jaw has a second set of six flat, plate-like teeth, a formidable feeding and fighting armamentarium.

The first dorsal spine, an identifying characteristic of the triggerfish family, Balistidae, is very heavy and can be raised to a vertical position. Set closely behind it is a shorter and less heavy spine which erects to about a 45 degree angle. The small spine acts as a trigger which locks the large spine in place until the “trigger” is released. Thus the name ‘triggerfish’. This feature is used by the fish for protection when it is being threatened. By swimming into a snug hole or fissure and erecting its spine, the fish effectively locks itself into place and makes its removal very difficult. Extending the spine also discourages a potential predator from trying to swallow the fish. This technique is also used when the fish is resting during the night.

The fused pelvic fins form a heavy spine on the lower border of the body. Pectoral fins are small and fused to a single spine. The body is covered with closely placed, heavy, rhomboid-shaped scales that create an almost armor plate skin.

This fish presents a variety of body colors including white, red, blue, black, brown, and yellow. The upper part of the head and back are light to rusty brown. The belly is white. There is a wide, black stripe from the eye to the base of the anal fin. The base of the pectoral fin is a bright, reddish-orange. The name “wedge-tail” derives from a black, wedge-shaped mark, extending from the posterior body side on to the caudal peduncle.

Size

Wedge-tails reach a maximum length of about 30.0 cm (11.8 in).

Diet and Feeding

Food preferences consist of a large variety of items including algae and different types of invertebrates such as echinoderms, snails, and other small mollusks, various worms, and small crustaceans. Wedge-tails will sometimes make use of their ability to blow a jet of water out of the mouth to uncover food items. The location of the eyes high on the long head gives this animal the ability to feed on long-spined sea urchins without being poked in the eye.

Reproduction

These fish are nesters and guarders. Eggs are deposited in a shallow, round depression on the substrate. The fish are very territorial and protective, especially the female, and are very vigorous in their protection of the nest and eggs. Eggs are demersal, but larvae are planktonic until they settle out to develop into juveniles. There appears to be a distinct pairing of the fish during the spawning season.

Behavior

Triggerfish are diurnal and spend most of their waking hours searching for food. Usually solitary, they are rarely seen in groups. Their swimming technique is similar to that of closely related families including puffers, file fish, and even the huge mola mola. It consists of an undulation of the dorsal and anal fins for forward and reverse movement and movement of the pectoral and caudal fins for directional control. If a burst of speed is required, the caudal fin is temporarily brought into play. These fish have exquisite maneuverability which is important in negotiating the intricacies of their reef habitat and avoiding pursuit by potential predators.

Adaptation

Members of this species are ideally adapted to their reef community habitat. Their swimming abilities, triggered dorsal spine, sturdy jaws, strong, sharp teeth, and heavily armored skin all contribute to the fish’s safety and well-being.

Wedge-tails, along with other species in the family, have the ability to modify their colors, especially when they are in a captive environment. If stressed their colors fade, but if comfortable in their surroundings, colors become bright and vivid.

Conservation

Wedge-tail triggerfish are edible. They were used for food by the early Hawaiians, but have never been a favored food fish. They have not had any significant commercial value. On occasion, they were a targeted species by the early Hawaiians, not for food, but dried and used as cooking fuel. In recent years with the increased popularity of home aquariums this sturdy, colorful and entertaining, if somewhat pugnacious fish, has become a very marketable item and in some areas commercial collectors are placing pressures on local populations that could create problems in the future.

At the present time the species is not evaluated by the IUCN Red List.

Amazing Facts

Snorkelers and divers tend to be wary of humu humus. Their swimming abilities, territorial nature, aggressiveness and sturdy, sharp teeth combine to create a formidable opponent from which humans sometimes find retreat advisable.

Pop culture has recognized the uniqueness of the humu humu fish in song, story, movies, and television, and a bicycle company named one of it models after this popular icon.