How to Identify Yellowfin Surgeonfish

To identify Yellowfin Surgeonfish (Acanthurus xanthopterus), look at these key features.

Physical Characteristics

Body shape

compressed

Coloration

Adults typically exhibit a grayish-brown to olive-brown body, often with fine, wavy longitudinal lines or a mottled pattern. The most distinguishing features are the bright yellow pectoral fins, a yellow caudal fin (though sometimes dusky or brownish), and a prominent yellow ring around the eye. A dark spot is often present at the posterior end of the dorsal fin base and sometimes at the anal fin base. Juveniles are generally yellow overall, gradually developing adult coloration.

Scale type

ctenoid

Mouth position

terminal

Distinctive features

Bright yellow pectoral fins, Yellow caudal fin (often with a dusky margin), Yellow ring around the eye, Dark spot at the base of the dorsal fin, Scalpel-like spine on caudal peduncle

Dorsal fin

IX spines, 25-27 soft rays; long and continuous.

Tail fin

Lunate to emarginate, typically yellow with a dusky posterior margin.

Pectoral fin

16-17 rays; bright yellow, providing a key identification feature.

Distinctive fins

Pelvic fins I spine, 5 rays; anal fin III spines, 23-25 soft rays.

Identification Tips

1. 1

   Pectoral Fins

   The most reliable identifier is the bright yellow coloration of the pectoral fins, which is consistent across all life stages.

2. 2

   Caudal Fin

   The caudal fin is typically yellow, though it can be dusky or brownish, especially towards the posterior margin. This contrasts with the body color.

3. 3

   Eye Ring

   A distinct yellow ring around the eye is a consistent feature in adults.

4. 4

   Body Coloration

   Adults are generally grayish-brown to olive-brown, often with subtle longitudinal lines or mottling. Juveniles are bright yellow.

5. 5

   Size

   This is one of the larger surgeonfish species, reaching up to 56 cm (22 inches) in total length.

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