How to Identify Unicorn Fish

To identify Unicorn Fish (Naso unicornis), look at these key features.

Physical Characteristics

Body shape

compressed

Coloration

Adults are typically olive-brown to grayish-blue, often with a lighter belly. The caudal fin has a broad, pale posterior margin. Two prominent blue or black bony plates (keels) are present on each side of the caudal peduncle, each bearing a sharp, forward-pointing spine. Juveniles are generally more uniformly gray.

Scale type

ctenoid

Mouth position

terminal

Distinctive features

A prominent, bony, horn-like projection on the forehead, extending forward from between the eyes (more developed in adults)., Two sharp, forward-pointing spines on each side of the caudal peduncle, often highlighted in blue or black., A relatively small mouth., Large, lunate (crescent-shaped) caudal fin in adults.

Dorsal fin

VI spines, 27-30 soft rays; continuous, relatively low.

Tail fin

Lunate (crescent-shaped) in adults, truncate in juveniles.

Pectoral fin

17-19 rays; relatively long and pointed.

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

   Horn-like projection

   The most distinguishing feature is the bony horn on the forehead, which is absent in very young juveniles but grows with age. It is a solid, non-retractable structure.

2. 2

   Caudal peduncle spines

   Look for two prominent, often blue or black, bony plates on each side of the caudal peduncle, each armed with a sharp, forward-pointing spine. These are characteristic of all Naso species.

3. 3

   Caudal fin shape

   Adults possess a distinctly lunate (crescent-shaped) caudal fin, which is a key identifier compared to other tangs.

4. 4

   Coloration

   The overall olive-brown to grayish-blue body color with a pale caudal fin margin helps differentiate it from other unicornfish species.

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