European flounder (Platichthys flesus)

Photo by Daniel Benák on iNaturalist · CC BY 4.0

Fish·Active (October)

European flounder

Platichthys flesus

When
May–Dec — May, June, July, August, September, October, November, December. Earlier where the water warms first.
Habitat
Estuaries, harbours, shallow sandy bays and the lower reaches of rivers, often in very shallow water close to the edge. In Britain flounder have been found far up the Severn, Dovey and Wyre.
Identification
An oval flatfish, usually with both eyes on the right side, dull brown or olive above with darker blotches and sometimes reddish spots, pearly white below. The skin is rough, with rows of prickly bumps along the lateral line and the bases of the fins.
Notes
The one European flatfish that lives much of its life in fresh and brackish water. It feeds on the bottom, mostly by night, on worms, shrimps and shellfish, and moves to deeper water at sea in winter to spawn in spring.
Method
Ragworm or lugworm on a light, two- or three-hook flapper rig with beads or a small spoon, cast short into the channel edges.
Caution
Minimum sizes vary — 20 cm on France’s Atlantic and Channel coasts — and rules differ between tidal and fresh water; check locally.

Seasons, size limits and catch limits change every year and differ by water body. Check the current regulations for the country and the water before fishing.

European flounder facts

Also called
Flounder or white fluke; flet in French.
Family
Pleuronectidae, the righteye flounders.
Native range
Coastal and brackish waters of Europe from the White Sea and the Baltic to the Mediterranean, the Black Sea and the North African coast; established in Iceland since 1999.
Introduced to
Carried to the North American Great Lakes in ships’ ballast water in the 1970s, but only a few were ever found and it probably did not breed there.
Habitat
Mud and sand from the shore down to about 100 m (330 ft), and estuaries, where it spends much of the year; it often runs far up rivers into fresh water.
Water temperature
Cool temperate. AquaMaps puts its preferred surface water at about 9–16°C (48–61°F); FishBase gives a tolerance of 5–25°C.
Size
Most adults 25–40 cm (10–16 in); the largest measured about 60 cm (24 in).
Record
IGFA all-tackle world record: 2.93 kg (6 lb 7 oz), Anne Karin Lothe, Maurangerfjorden, Norway, 10 January 2004.
Lifespan
Up to 15 years.
What it eats
Worms, shrimps, snails and bivalves, and small fish; young fish eat plankton and insect larvae.
Spawning
Adults move to deeper, warmer water at sea in winter and spawn there in spring; each female sheds 0.4–2 million eggs. The larvae ride the tides into estuaries and up rivers.
Young fish
Larvae and young flounder ride the tides upstream into rivers, cued by salinity, food and water temperature.
Teeth and mouth
Small, at the end of a bluntly pointed snout.
Look-alikes
Plaice has smooth skin, a bony ridge behind the eyes and bright orange spots. The flounder may show reddish spots too, but its rough skin and the prickly bumps along the lateral line and fin bases give it away. The two sometimes hybridise.
Eating
A commercial food fish, sold fresh and frozen in Europe.
Status
Least Concern on the IUCN Red List (2022).

Interactive

European flounder: size range

Move the slider from a typical adult to the largest recorded specimen, shown against objects of known size.

33 cm · 13 inmost adults10203040506070cm369121518212427ina grown-up's hand · 18 cma loaf of bread · 30 cm

Most adults you'll catch: 25–40 cm (10–16 in).

This european flounder: 33 cm. Longer than a loaf of bread, shorter than a four-year-old.

The record

IGFA all-tackle world record: 2.93 kg (6 lb 7 oz), Anne Karin Lothe, Maurangerfjorden, Norway, 10 January 2004.

Questions people ask about european flounder

Can flounder live in fresh water?

Yes. Unlike other European flatfish, the flounder regularly runs up rivers and feeds in fresh water before returning to the sea to spawn. In Britain it has been found as far inland as Montgomeryshire on the River Severn.

How do you tell a flounder from a plaice?

Run a finger along the lateral line: a flounder is rough, with rows of prickly bumps along it and at the base of the fins. A plaice is smooth, with bright orange spots and a bony ridge behind the eyes.

When is the best time to catch flounder?

Spring through autumn in estuaries and shallow bays. In late winter and early spring many adults are offshore spawning, and catches drop.

Found in these regions

Checked against these sources ·

Sizes, records and ranges are for the species as a whole; local populations and rules vary. Records change; the record-keeper named above holds the current one.

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Also active in October