How to Identify Orange-lined Triggerfish

To identify Orange-lined Triggerfish (Balistapus undulatus), look at these key features.

Physical Characteristics

Body shape

compressed

Coloration

The body is typically dark green to brown, adorned with numerous wavy, bright orange to reddish-brown lines that run horizontally and diagonally across the body. The caudal fin is often yellowish to orange, and there is a prominent black spot at the base of the pectoral fins. The eyes are often ringed with orange.

Scale type

none

Mouth position

terminal

Distinctive features

Prominent first dorsal spine that can be locked into an upright position (trigger mechanism)., Small, terminal mouth with strong, chisel-like teeth., Rough, leathery skin with small, non-overlapping scales., Distinctive wavy orange lines on a dark body., Black spot at the pectoral fin base.

Dorsal fin

Two dorsal fins; the first with 3 spines (the first being large and lockable), and the second with 24-27 soft rays. The first dorsal spine is robust and used for wedging itself into crevices.

Tail fin

Slightly rounded to truncate caudal fin, often yellowish or orange.

Pectoral fin

Small, rounded pectoral fins with 13-15 rays.

Distinctive fins

Anal fin with 20-23 soft rays, mirroring the shape of the second dorsal fin. Pelvic fins are reduced to a single, rough spine-like structure.

Identification Tips

1. 1

   Coloration and Pattern

   Look for the distinctive wavy orange or reddish-brown lines on a dark green to brown body. This pattern is unique among triggerfish.

2. 2

   Pectoral Fin Spot

   A prominent black spot at the base of the pectoral fins is a key identifying feature.

3. 3

   Body Shape

   Its compressed, oval body and small, high-set eyes are typical of triggerfish.

4. 4

   Behavior

   Observe its solitary and territorial nature, often seen patrolling a specific area of the reef.

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