How to Identify Sleek Unicornfish

To identify Sleek Unicornfish (Naso hexacanthus), look at these key features.

Physical Characteristics

Body shape

compressed

Coloration

Adults are typically dark grey to brownish-grey dorsally, fading to lighter grey or whitish ventrally. They often exhibit a yellowish or orange band along the dorsal and anal fin bases, and the caudal fin can be dark with a pale posterior margin. Juveniles are generally lighter in color. During spawning or stress, color patterns can intensify or change.

Scale type

ctenoid

Mouth position

terminal

Distinctive features

Absence of a prominent frontal horn in adults (distinguishing it from many other Naso species)., Two prominent, fixed bony plates (scalpel-like spines) on each side of the caudal peduncle, which are bright orange or yellow., A relatively small mouth., Streamlined, elongated body shape.

Dorsal fin

Single dorsal fin with 5-6 spines and 27-30 soft rays. The anterior soft rays are often elongated in males.

Tail fin

Lunate (crescent-shaped) caudal fin, often with elongated filaments on the upper and lower lobes in mature males.

Pectoral fin

Pectoral fins are relatively small and rounded.

Distinctive fins

Anal fin with 2 spines and 27-30 soft rays. Pelvic fins with 1 spine and 3 soft rays.

Identification Tips

1. 1

   Absence of Horn

   Unlike many other unicornfish, adult Naso hexacanthus lacks a prominent bony protuberance (horn) on its forehead. This is a key differentiator.

2. 2

   Caudal Peduncle Spines

   Look for two bright orange or yellow, fixed, scalpel-like spines on each side of the caudal peduncle (the narrow part of the body before the tail fin). These are characteristic of surgeonfish and are particularly prominent and colored in this species.

3. 3

   Body Coloration

   Observe the overall dark grey to brownish-grey body, often with yellowish or orange bands at the base of the dorsal and anal fins. The caudal fin is typically dark with a pale posterior margin.

4. 4

   Fin Shape

   Note the lunate (crescent-shaped) caudal fin, which may have elongated filaments in mature males. The anterior soft rays of the dorsal fin can also be elongated in males.

5. 5

   Schooling Behavior

   Sleek Unicornfish are often observed in large schools in open water near reef drop-offs, which can aid in identification.

Explore Sleek Unicornfish