How to Identify Sergeant Major

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

Physical Characteristics

Body shape

compressed

Coloration

Adults typically have a silvery-white to yellowish body with five prominent black vertical bars. The fins are often dusky or yellowish. During breeding, males can exhibit a striking blue-purple coloration, especially on the head and anterior body, with the black bars becoming more intense.

Scale type

ctenoid

Mouth position

terminal

Distinctive features

Five prominent black vertical bars on a light body., Deeply forked caudal fin., Small, terminal mouth., Relatively large eyes.

Dorsal fin

Single dorsal fin with 13 spines and 11-13 soft rays. The spinous and soft-rayed portions are continuous.

Tail fin

Deeply forked caudal fin, often with dusky tips.

Pectoral fin

Large and somewhat pointed pectoral fins, typically clear to yellowish.

Distinctive fins

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

Identification Tips

1. 1

   Vertical Bars

   The most defining characteristic is the presence of five distinct black vertical bars on a light (silvery-white to yellowish) body. These bars extend from the dorsal fin to the ventral side.

2. 2

   Body Shape

   Laterally compressed, oval-shaped body, typical of damselfishes.

3. 3

   Caudal Fin

   Deeply forked tail fin, which is often dusky or yellowish.

4. 4

   Breeding Coloration

   During spawning, males develop a striking blue-purple hue, especially on the head and anterior body, making the black bars even more pronounced. This is a key indicator of reproductive activity.

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