How to Identify Humphead Unicornfish

To identify Humphead Unicornfish (Naso brachycentron), look at these key features.

Physical Characteristics

Body shape

compressed

Coloration

Adults are generally greyish-brown to olive-green dorsally, fading to lighter shades ventrally. The most distinctive feature is the prominent, often yellowish or bluish, bony horn on the forehead, which can extend significantly forward. The caudal fin has a broad, pale posterior margin. Juveniles are typically more uniformly grey.

Scale type

ctenoid

Mouth position

terminal

Distinctive features

Prominent bony horn on the forehead, developing with age (more pronounced in males), Distinct dorsal hump, particularly in larger individuals, Two bony plates on each side of the caudal peduncle, each bearing a sharp, fixed spine, Elongated, somewhat compressed body

Dorsal fin

VI spines, 27-30 soft rays; the anterior part of the soft dorsal fin is elevated, forming a hump.

Tail fin

Lunate (crescent-shaped) in adults, with elongated filaments on the upper and lower lobes in large males.

Pectoral fin

17-19 rays, relatively small.

Distinctive fins

Anal fin with II spines and 28-30 soft rays. Pelvic fins with I spine and 3 soft rays.

Identification Tips

1. 1

   Forehead Horn

   The most distinguishing feature is the prominent, often pointed, bony horn projecting from the forehead. This horn is absent in juveniles and develops with age, becoming more pronounced in mature males.

2. 2

   Dorsal Hump

   Adults possess a noticeable hump on their back, formed by the elevated anterior soft rays of the dorsal fin.

3. 3

   Caudal Peduncle Spines

   Like all surgeonfish, it has two sharp, fixed bony plates (scalpel-like spines) on each side of the caudal peduncle (the narrow part of the body connecting to the tail fin). These are a key family characteristic.

4. 4

   Caudal Fin Shape

   The caudal fin is lunate (crescent-shaped) in adults, with large males often developing elongated filaments on the upper and lower lobes.

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