How to Identify Tongue Sole

To identify Tongue Sole (Cynoglossus spp.), look at these key features.

Physical Characteristics

Body shape

elongated

Coloration

Dorsal side typically brownish to grayish, often mottled or spotted to blend with the substrate; ventral side is whitish. Coloration can vary significantly between species and individuals based on their environment.

Scale type

ctenoid

Mouth position

inferior

Distinctive features

Highly compressed, elongated, tongue-shaped body, Both eyes located on the left side of the head, very close together, Small, asymmetrical mouth, Absence of pectoral fins in most species, Dorsal and anal fins confluent with the caudal fin

Dorsal fin

Long, continuous, originating near the snout and confluent with the caudal fin.

Tail fin

Small, pointed, confluent with dorsal and anal fins, forming a continuous fringe.

Pectoral fin

Absent or rudimentary in most species.

Distinctive fins

Pelvic fins, if present, are small and often fused, located on the blind side.

Identification Tips

1. 1

   Body Shape

   Look for the characteristic elongated, flattened, tongue-like body. This is the most defining feature.

2. 2

   Eye Placement

   Both eyes are always on the left side of the head, very close together. This immediately distinguishes them from right-eyed flatfish.

3. 3

   Fins

   Observe the continuous dorsal, caudal, and anal fins forming a single fringe around the posterior body. Note the absence or extreme reduction of pectoral fins.

4. 4

   Mouth

   The mouth is small and asymmetrical, located on the underside of the head.

5. 5

   Lateral Line

   Many Cynoglossus species have multiple lateral lines on the ocular (eyed) side, which can be a key distinguishing feature between species within the genus.

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