Platichthys flesus is common around the British Isles, where it is typically found resting on the muddy substrate of estuaries. It has been found at a depth range of 1-100 m. It migrates into the open sea to breed from March to June, during which time it can migrate up to 300 km offshore, although it will more often migrate just 30 km. The larvae feed on copepods and diatoms and gradually shift to a diet of mysids, decapods, crustaceans, polychaetes, and bivalves. The young then return to estuarine waters, where they live on the bottom until they are ready to migrate and spawn.