Lined Unicornfish

Naso brevirostris, commonly known as the short-nosed unicornfish, is a notable species within the family Acanthuridae, which includes surgeonfishes, unicornfishes, and tangs. Distributed across the 🇮🇳 Indian and western 🌊 Pacific Oceans, this species was first officially documented in 1829 by the esteemed French zoologist Georges Cuvier. Although the precise type locality was not specified, it is generally believed to be 🇮🇩 Indonesia. This species is categorized under the nominate subgenus of the genus Naso, the sole genus within the Nasinae subfamily.

The specific epithet brevirostris, meaning "short nose," refers to the comparatively shorter snout of this species relative to the type species Naso fronticornis. Morphologically, Naso brevirostris is characterized by six spines and between 27 to 29 soft rays supporting the dorsal fin, with the anal fin supported by two spines and 27 to 29 soft rays. The body depth is proportionate to the standard length, fitting into it approximately 2 to 2.7 times. The snout is notably abrupt and steep. As the fish matures, it develops elongated bony protuberances anterior to the eyes, which may extend up to the length of the head. Bony plates with underdeveloped keels are present on each side of the caudal peduncle, and the caudal fin ranges from truncate to slightly rounded.

The coloration of Naso brevirostris varies from light blueish-grey to olive-brown. An alternate color phase presents a distinctively pale anterior quarter with a clear boundary separating it from the rest of the body. The flanks exhibit fine, vertical dark grey lines that transform into spots lower down the body, while the head is adorned with small dark spots or a lattice pattern. The bony protuberance is distinguished by diagonal black lines, and additional features include white operculum membrane, pale blue-edged lips, and a predominantly whitish caudal fin. The species can attain a maximum total length of 60 cm (24 inches).

Naso brevirostris is prevalent throughout an extensive range covering the 🇮🇳 Indian and 🌊 Pacific Oceans, from the 🌊 Red Sea and along the eastern African coast to Durban, 🇿🇦 South Africa, spanning eastward to the Western Pacific, reaching areas such as the Pitcairn Islands and the Hawaiian Islands, north to southern 🇯🇵 Japan, and south to 🇦🇺 Australia. Within 🇦🇺 Australia, its presence extends from Ningaloo Reef, around the northern tropical coasts, to the northern Great Barrier Reef and the Coral Sea, reaching as far south as Moreton Bay in Queensland, and includes the Lord Howe Island region in the Tasman Sea. In the eastern Pacific, it is found near the Galápagos Islands.

Habitat preferences for Naso brevirostris include lagoon and seaward reefs, with a depth range extending to 46 meters (151 feet). The species is known to form spawning aggregations and engage in pair spawning, with males exhibiting larger caudal peduncle keels than females. The resulting eggs develop into pelagic larvae that can remain in the water column for up to 90 days. Sexual maturity is typically achieved at a length of approximately 25 cm (9.8 inches). The dietary habits of the species evolve as it matures; adults primarily consume gelatinous zooplankton, whereas juveniles feed on benthic algae, with the dietary shift coinciding with the development of their distinctive bony protuberance.

While Naso brevirostris is often caught for consumption through methods such as fish traps and spearing, it is important to note that there have been instances of Ciguatera fish poisoning associated with its consumption.