Flounder

Where it lives

European flounder are unusual among flatfish for their tolerance of brackish and even freshwater conditions — they routinely enter rivers tens of kilometers above tide. Adults occupy estuaries, coastal flats, and the continental shelf from 0 to 100 m.

How to recognise it

A right-eyed flatfish (though left-eyed individuals are not rare). The eyed side is brown to greenish with diffuse pale and dark spots that often include orange-tinged blotches. Stiff bony tubercles run along the lateral line and the bases of the dorsal and anal fins.

Diet & behavior

Flounder feed on polychaetes, amphipods, crabs, shrimps, mollusks, and small fish. They are crepuscular and partially active by day in turbid water. Spawning happens at sea in spring; larvae drift into estuaries to develop.

Fisheries & Conservation

Globally Least Concern. A minor commercial species across northern Europe; large U.S. flounders (summer, southern, winter) are separate species in the same family.