Platichthys flesus (Platichthys flesus flounder juv.) preys on:
Sprattus sprattus
Clupea harengus
Anguilla anguilla
Ammodytes tobianus
Pholis gunnellus
Pomatoschistus microps
Myxocephalus scorpius
Pleuronectes platessa
Platichthys flesus
Crangon crangon
Nereis diversicolor
Nereis virens
Phyllodoce mucosa
Copepoda
Balanus balanoides
Neomysis integer
Talitrus saltator
Corophium volutator
Bathyporeia pilosa
Gammarus
Idotea emarginata
Jaera albifrons
Eurydice pulchra
Nototropis
Pygospio elegans
Capitella capitata
Manayunkia aestuarina
Aricia
Arenicola marina
Tubificoides benedii
Tubifex costatus
Littorina littorea
Alderia modestus
Retusa obtusa
Mya arenaria
Macoma balthica
Mytilus edulis
Cerastoderma edule
Chironomidae
Diptera
Hesionidae
Enteromorpha
Eteone longa
Foraminifera

Based on studies in:
Scotland (Estuarine)

This list may not be complete but is based on published studies.