The Wedgetail Triggerfish (Rhinecanthus rectangulus) is a strikingly patterned reef fish found in the tropical and subtropical Indo-West Pacific from the Red Sea through Indonesia to the Marquesas Islands, north to southern Japan and south to Lord Howe Island. These fish can be found at depths to around 20 m around shallow coral or rocky reefs exposed to surge. They feed on corals and encrusting organisms, which they snap off with their strong teeth (the mouth is small, but both jaws bear strong incisors). (van der Elst 1993; Matsuura 2001)
Wedgetail Triggerfish have an orange snout and a bright blue band running over the upper jaw. A broad black or dark brown band extends diagonally across the body from the eye to the anal fin, completely separating the upper flanks from the head and pale chest. The caudal peduncle, at the base of the caudal (tail) fin has a black triangular blotch coming to a point below the middle of second the dorsal fin. The fins are dusky to translucent. The large, rounded pectoral fins (just behind the small, round gill openings) are marked with a fine vertically oriented curved orange bar. (van der Elst 1993; Matsuura 2001)
The somewhat angular body is covered with distinct rhomboid scales arranged in a regular "criss-cross" pattern. The modified scales running longitudinally on either side of the caudal peduncle carry five rows of short, sharp spikes. The first dorsal fin consists of three spines and the second consists of 22 to 24 rays. As with all triggerfishes, the first dorsal spine is very stout and can be locked into an upright position by the 2nd spine, or trigger. The spineless anal fin has 20 rays. The pelvic fins are reduced to a spiny projection at the lowest part of the body. Maximum length is around 25 cm. (van der Elst 1993; Matsuura 2001)
Wedgetail Triggerfish are easily approached underwater, but once alarmed the fish typically swims into a small crevice and lodge itself there by erecting its dorsal and pelvic spines (even if the tail remains exposed, the sharp caudal spikes offer some protection). If persistently harrassed, the triggerfish will repeat a series of short grunts. (van der Elst 1993)
Little is known about the breeding cycle of this species, but the fact that very small specimens are seen on reefs during the summer suggests a late winter spawning season. Wedgetail triggerfish are popular aquarium fish. They are easily caught on a small hook, but are not generally eaten. (van der Elst 1993) The Wedgetail Triggerfish is a familiar icon—and the official state fish-- in Hawaii, where it is known as the humuhumunukunukuapuaʻa. (Wikipedia [17 February 2012] and references therein)
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