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.
The Pacific halibut is found in the northern Pacific Ocean. This species lives near the seafloor, often at depths between 50 and 2000 metres. They occasionally hunt at lesser depths for squid. This species of halibut has a lifespan of up to 55 years and reaches lengths of 2.60 metres. These fish then weigh around 360 kilograms.