How to Identify Planehead Filefish

To identify Planehead Filefish (Monocanthus hispidus), look at these key features.

Physical Characteristics

Body shape

compressed

Coloration

Highly variable, ranging from mottled browns, greens, and grays to match their surroundings. Often displays irregular spots, blotches, and lines. Can change color rapidly to enhance camouflage. Juveniles may have more pronounced patterns.

Scale type

none

Mouth position

terminal

Distinctive features

First dorsal spine is prominent, stout, and can be locked upright by a second, smaller spine, giving the 'filefish' appearance., Small, terminal mouth with incisor-like teeth., Rough, sandpaper-like skin due to numerous small, bristly scales., Pelvic fin reduced to a spine-like structure, often with a dewlap of skin., Eyes are relatively large and can move independently.

Dorsal fin

Two dorsal fins; the first with 2 spines (the first spine is large and erectile, the second is small and locks the first), the second dorsal fin is soft-rayed with 30-37 rays. The soft dorsal fin is long and low.

Tail fin

Rounded to slightly truncate caudal fin with 12 rays.

Pectoral fin

Small, rounded pectoral fins with 12-14 rays, positioned high on the body.

Distinctive fins

Anal fin is similar in shape and size to the soft dorsal fin, with 31-37 rays. Pelvic fin is represented by a single, rough spine, often associated with a prominent dewlap of skin that can be extended or retracted.

Identification Tips

1. 1

   Dorsal Spine

   The most distinguishing feature is the large, erectile first dorsal spine that can be locked into an upright position. This gives the fish its 'file-like' appearance.

2. 2

   Body Shape and Texture

   Laterally compressed, oval body with rough, bristly skin. The skin texture is a key differentiator from other fish families.

3. 3

   Coloration and Pattern

   Highly variable and cryptic, often matching the surrounding environment. Look for mottled patterns of browns, greens, and grays, which can change rapidly.

4. 4

   Mouth and Eyes

   Small, terminal mouth with incisor-like teeth. Relatively large eyes that can move independently, aiding in camouflage and prey detection.

5. 5

   Pelvic Fin

   Reduced to a single, rough spine, often accompanied by a prominent dewlap of skin that can be extended or retracted.

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