Plaice is a common name for a group of flatfish that comprises four species: the European, American, Alaskan and scale-eye plaice. Commercially, the most important plaice is the European. 
 
As plaice is a flat fish, the top and bottom fillets look very different, even though they are from the same fish. The skin on the top fillet will be a dark, brownish colour with orange spots. The skin on the bottom fillet will be white.