How to Identify Ocean Surgeonfish

To identify Ocean Surgeonfish (Acanthurus tractus), look at these key features.

Physical Characteristics

Body shape

compressed

Coloration

Adults typically exhibit a grayish-brown to dark brown body coloration, often with faint, irregular pale spots or lines. The caudal fin is usually dark, sometimes with a pale posterior margin. Juveniles are often bright yellow, gradually changing to the adult coloration as they mature. Some individuals may display a pale bar behind the eye or a pale area on the caudal peduncle. Coloration can vary with mood and environment.

Scale type

ctenoid

Mouth position

terminal

Distinctive features

Oval, compressed body, Scalpel-like spine on each side of the caudal peduncle (retractable), Small, terminal mouth with a single row of spatulate teeth, Continuous dorsal fin

Dorsal fin

Single, long dorsal fin with 9 dorsal spines and 23-26 soft rays.

Tail fin

Lunate (crescent-shaped) caudal fin.

Pectoral fin

Relatively small, fan-shaped pectoral fins.

Distinctive fins

Anal fin with 3 spines and 21-24 soft rays. Pelvic fins with 1 spine and 5 soft rays.

Identification Tips

1. 1

   Body Coloration

   Adults are generally dark brown to grayish-brown, sometimes with faint mottling. Juveniles are bright yellow.

2. 2

   Caudal Spine

   Presence of a sharp, retractable spine on each side of the caudal peduncle (tail base), characteristic of all surgeonfishes.

3. 3

   Body Shape

   Distinctly oval and laterally compressed body.

4. 4

   Mouth

   Small, terminal mouth with specialized teeth for scraping algae.

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