Flatfish belong to the order Pleuronectoformes. There are more than 500 species of flatfish. Flatfish live on and partly in the seabed, only the halibut swims higher up in the water column. Flatfish have an oblong, flat shape and their eyes on one side. The upper-side, the eye-side, of the flatfish has a camouflage colour and the underside is white. It may seem like flatfish swim on their belly, however, in fact, they are laying on their side. Flatfish larvae have a regular fish shape, with eyes on each side and a vertical swimming mode. After 6 weeks, one of the eyes migrates upwards, over the head to the other side. From now own, the flatfish swims with their eyes up and their blind side facing the seabed.
The best known flatfish species in the Netherlands are sole and plaice. Other flatfish species that occur in the North Sea are the common dab, halibut, turbot, brill, European flounder and lemon sole. Flatfish are caught with beam trawls, pulse trawls or demersal otter trawls.
A lot of flatfish, which is caught in the Pacific Ocean, can be found on the Dutch market, especially yellowfin sole and rock sole. These flatfish can reach up to 60 cm in length and have a lifespan of 22 years. Yellowfin sole can be found in the northern part of the Pacific Ocean at depths of up to 550 metres.