How to Identify Summer Flounder

To identify Summer Flounder (Paralichthys dentatus), look at these key features.

Physical Characteristics

Body shape

flat

Coloration

Highly variable, ranging from olive-brown to gray, often with scattered dark spots and blotches, including 5-14 ocellated (eye-like) spots on the eyed side. The blind side is typically white. Capable of rapid color changes to match substrate.

Scale type

ctenoid

Mouth position

terminal

Distinctive features

Left-eyed flatfish (eyes on the left side of the head), Large mouth with prominent, sharp teeth, Dorsal fin origin anterior to the upper eye, Lateral line with a distinct arch over the pectoral fin, 5-14 ocellated spots on the eyed side (though these can be faint or absent in some individuals)

Dorsal fin

Long, continuous fin extending from the head to the caudal peduncle, typically with 85-94 soft rays.

Tail fin

Rounded to slightly truncate caudal fin.

Pectoral fin

Well-developed, fan-like pectoral fins; the one on the eyed side is larger.

Distinctive fins

Anal fin is also long and continuous, with 60-73 soft rays, mirroring the dorsal fin.

Identification Tips

1. 1

   Eye Placement

   Always check the eye placement. Summer Flounder are 'left-eyed,' meaning both eyes are on the left side of the head when viewed from above, with the mouth pointing away from you. This distinguishes them from 'right-eyed' flounders like Winter Flounder (Pseudopleuronectes americanus).

2. 2

   Mouth Size and Teeth

   The Summer Flounder has a relatively large mouth that extends to or beyond the posterior margin of the lower eye, armed with prominent, sharp teeth. This indicates its predatory nature.

3. 3

   Ocellated Spots

   Look for 5-14 distinct, dark, ocellated (eye-like) spots on the eyed side of the body. While these can sometimes be faint, their presence is a strong indicator. Other flounder species may have spots, but not typically these distinct ocelli.

4. 4

   Lateral Line

   Observe the lateral line, which has a distinct, high arch over the pectoral fin. This is a key morphological feature for identification.

5. 5

   Dorsal Fin Origin

   The origin of the dorsal fin is anterior to the upper eye, a characteristic of the family Paralichthyidae.

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