How to Identify Sergeant Major

To identify Sergeant Major (Abudefduf vaigiensis), look at these key features.

Physical Characteristics

Body shape

compressed

Coloration

Adults typically exhibit a silvery-white to yellowish body with 5-7 prominent black vertical bars. The caudal fin is often yellowish, and the dorsal fin may have a yellowish tint. Juveniles are often brighter yellow with more distinct black bars. During breeding, males can display a darker, almost purplish coloration, and the bars may become less distinct.

Scale type

ctenoid

Mouth position

terminal

Distinctive features

5-7 prominent black vertical bars on a silvery-white to yellowish body., Deeply forked caudal fin., Relatively small mouth., Large eyes.

Dorsal fin

Single dorsal fin with 13 spines and 12-14 soft rays. The spiny and soft-rayed portions are continuous.

Tail fin

Deeply forked caudal fin, often with yellowish coloration.

Pectoral fin

Large, fan-like pectoral fins, typically clear or slightly yellowish.

Distinctive fins

Pelvic fins are typically clear to slightly dusky, originating just behind the pectoral fin base.

Identification Tips

1. 1

   Vertical Bars

   Count the number of distinct black vertical bars on the body. Abudefduf vaigiensis typically has 5-7 bars, with the first often over the operculum and the last on the caudal peduncle.

2. 2

   Caudal Fin

   Observe the caudal (tail) fin, which is deeply forked and often has a yellowish hue, especially in adults.

3. 3

   Body Shape

   Note the compressed, oval-shaped body, typical of damselfishes.

4. 4

   Size

   Adults typically reach a maximum standard length of 20 cm (8 inches), though most commonly observed around 10-15 cm (4-6 inches).

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