How to Identify European Flounder

To identify European Flounder (Platichthys flesus), look at these key features.

Physical Characteristics

Body shape

flat

Coloration

Dorsal side is typically olive-brown to grey-brown, often mottled with darker spots and blotches, allowing for excellent camouflage. The ventral side (blind side) is white. Some individuals may exhibit orange or reddish spots. Coloration can change rapidly to match the substrate.

Scale type

ctenoid

Mouth position

terminal

Distinctive features

Eyes typically on the right side (dextral), but a significant proportion (up to 30%) can be left-eyed (sinistral)., Lateral line has a distinct curve above the pectoral fin., Rough, bony tubercles or plates along the bases of the dorsal and anal fins, and sometimes along the lateral line, giving a rough feel., Small, terminal mouth with small teeth.

Dorsal fin

Long, extending from behind the eye to the caudal peduncle, with 55-69 soft rays. Originates above the upper eye.

Tail fin

Rounded or slightly truncate, distinct from dorsal and anal fins.

Pectoral fin

Small, rounded, present on both sides.

Distinctive fins

Anal fin is also long, with 39-52 soft rays, extending from the vent to the caudal peduncle. Pelvic fins are small and located anterior to the anal fin.

Identification Tips

1. 1

   Eye Placement

   While typically right-eyed (dextral), a notable percentage (up to 30%) are left-eyed (sinistral). This variability is a key characteristic, distinguishing it from many other flatfish that are consistently one-sided.

2. 2

   Roughness of Skin

   Feel for the distinct row of bony tubercles or plates along the bases of the dorsal and anal fins. This gives the skin a noticeably rough texture, especially when compared to smoother flatfish like plaice.

3. 3

   Lateral Line

   Observe the lateral line, which has a distinct, often pronounced, arch or curve above the pectoral fin on the eyed side.

4. 4

   Coloration and Spots

   The dorsal side is typically dull brown or grey-brown, often mottled. While some individuals may have faint reddish or orange spots, these are generally less prominent and less numerous than the bright orange spots of a European Plaice (Pleuronectes platessa).

Explore European Flounder