Plaice is a medium sized flatfish. It has a smooth skin as opposed to, for example, dab and long rough dab. It is easily recognized by the red or orange spots on the otherwise dark back, the underside is white. The maximum recorded size in Icelandic waters is 33 inches, but the usual size in catches is from 12 to 20 inches. Plaice is common all around Iceland from the seashore to 650 feet depth, on sandy or muddy bottoms. It can also tolerate fresh waters for some time. In European waters it is found from the White Sea and the Barents Sea in the north down to the western part of the Mediterranean Sea in the south. It is not found in North American waters. Previously, flatfishes were considered rather sedentary. Tagging studies on the plaice have, however, shown that this does not hold entirely true. The plaice undertakes large scale feeding and spawning migrations in the waters around Iceland, fishes tagged on one side of the country have even found at the other side.
Spawning mostly takes place in the warmer waters south and west of Iceland at 165 to 330 feet depth. Eggs and larvae have also been found in colder northern waters, so at least some limited spawning also occurs there. In the southern waters, the peak spawning season is in March and April but in May and June in northern waters. The juveniles settle onto shallow intertidal beaches and stay there for the first year of their life before migrating to deeper waters.
Plaice is relatively fast growing and can reach a larger size than other flatfish species in Icelandic waters, with the exception of halibut and Greenland halibut. Females grow larger than males as is common with flatfishes. Growth is, however, quite variable and has been shown to depend on temperature, food abundance and stock size, among other things. The plaice reaches 50% maturity at around the age of 5, maximum age being more than 20 years. Plaice feeds mainly on various benthic invertebrates, dominated by polychaetes and bivalves, but also, to some extent, on small fishes such as sandeels.