How to Identify Reef Triggerfish

To identify Reef Triggerfish (Rhinecanthus rectangulus), look at these key features.

Physical Characteristics

Body shape

compressed

Coloration

The body is predominantly light tan to yellowish-brown, with a striking black wedge-shaped marking on the posterior half of the body, extending from the dorsal fin base to the anal fin base. A prominent black band runs from the eye to the pectoral fin base, and another black band encircles the mouth. The caudal fin is yellow, and there are often blue or purple lines around the eyes and mouth.

Scale type

ganoid

Mouth position

terminal

Distinctive features

First dorsal spine can be locked upright, giving the 'trigger' mechanism., Small, terminal mouth with strong teeth., Rough, leathery skin with small, non-overlapping scales., Distinctive black wedge-shaped marking on the posterior body., Black band from eye to pectoral fin and around the mouth.

Dorsal fin

Two dorsal fins; the first consists of three spines, with the first spine being large and capable of being locked upright by the second spine. The second dorsal fin is soft-rayed and mirrors the anal fin in shape and size.

Tail fin

Slightly rounded to truncate caudal fin, typically yellow.

Pectoral fin

Small, rounded pectoral fins.

Distinctive fins

Pelvic fins are fused into a single, spiny flap-like structure.

Identification Tips

1. 1

   Body Pattern

   Look for the characteristic black wedge-shaped marking on the rear half of the body, resembling a rectangle or a wedge. This is the most definitive feature.

2. 2

   Facial Markings

   Observe the black band running from the eye to the pectoral fin and the black band encircling the mouth. These are consistent across individuals.

3. 3

   Caudal Fin Color

   The bright yellow caudal fin is a good indicator, especially in contrast to the body coloration.

4. 4

   Trigger Mechanism

   While not always visible, the ability to lock the first dorsal spine upright is a key characteristic of all triggerfish, including this species.

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