How to Identify White-faced Surgeonfish

To identify White-faced Surgeonfish (Acanthurus nigricans), look at these key features.

Physical Characteristics

Body shape

compressed

Coloration

The body is predominantly dark brown to black. A distinctive, prominent white patch is located directly below the eye, extending slightly onto the operculum. The dorsal and anal fins are dark, often with a thin blue or white margin. The pectoral fins are dark with a yellow base. The caudal fin is bright yellow, often with a thin dark posterior margin. Juveniles may have a more yellowish body with the characteristic white cheek patch.

Scale type

ctenoid

Mouth position

terminal

Distinctive features

Prominent white patch below the eye, Bright yellow caudal fin, Dark body coloration, Scalpel-like spine on each side of the caudal peduncle

Dorsal fin

Single, long dorsal fin with 8-9 spines and 24-27 soft rays. The spiny and soft-rayed portions are continuous.

Tail fin

Lunate (crescent-shaped) caudal fin, bright yellow.

Pectoral fin

Relatively small, fan-shaped pectoral fins, dark with a yellow base.

Distinctive fins

A single, sharp, retractable scalpel-like spine on each side of the caudal peduncle (tail base), characteristic of all surgeonfishes.

Identification Tips

1. 1

   White patch below eye

   This is the most defining characteristic. Look for a distinct, bright white blotch directly beneath the eye.

2. 2

   Caudal fin color

   The tail fin is a vibrant yellow, contrasting sharply with the dark body.

3. 3

   Body color

   The main body is a uniform dark brown to black.

4. 4

   Pectoral fin base

   A yellow coloration at the base of the pectoral fins is often visible.

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