How to Identify Leatherjacket

To identify Leatherjacket (Monacanthidae), look at these key features.

Physical Characteristics

Body shape

compressed

Coloration

Highly variable, ranging from drab browns and greens to vibrant patterns of spots, stripes, and blotches. Many species exhibit cryptic coloration, allowing them to blend into their environment. Coloration can also change rapidly based on mood or environment.

Scale type

none

Mouth position

terminal

Distinctive features

Rough, leathery skin due to small, bristly scales, Small, protractile mouth with strong, incisor-like teeth, First dorsal spine is large and erectile, locking into place with a smaller second spine, Pelvic fin reduced to a spine or absent, often with a dewlap of skin, Eyes are typically set high on the head

Dorsal fin

Two dorsal fins; the first consists of 1-3 spines (usually 1 large, erectile spine followed by a smaller locking spine), and the second is soft-rayed (23-52 rays).

Tail fin

Caudal fin is typically rounded or truncate, with 10-13 rays.

Pectoral fin

Small, rounded pectoral fins, typically with 10-15 rays.

Distinctive fins

Anal fin is soft-rayed (20-49 rays) and mirrors the shape of the second dorsal fin. Pelvic fins are either absent or reduced to a single, often rough, spine, sometimes associated with a prominent dewlap of skin that can be used to expand the ventral profile.

Identification Tips

1. 1

   Dorsal Spine

   Look for the prominent, erectile first dorsal spine that can be locked upright. This is a key distinguishing feature from other fish families.

2. 2

   Skin Texture

   Feel the skin if possible (with caution). It will be rough and sandpaper-like, unlike the smooth skin of many other fish.

3. 3

   Mouth

   Observe the small, often upturned mouth with strong, incisor-like teeth, adapted for nipping at prey.

4. 4

   Body Shape

   Note the highly compressed, often deep body, which gives them a flattened appearance when viewed head-on.

5. 5

   Pelvic Fin

   Check for the reduced or absent pelvic fin, often replaced by a rough spine or a prominent dewlap of skin.

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