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common name for any member of the unique and widespread order Pleuronectiformes containing over 500 species (including the flounder, halibut, plaice, sole, and turbot), 130 of which are American. Flatfishes are common in both the Atlantic and Pacific; many are important food and game fishes. All flatfishes have an unusual flattened body form well suited to life on the bottom. The development of the young flatfish recapitulates to some degree the probable evolutionary process. The newly hatched transparent larvae are bilaterally symmetrical, but soon the characteristic compression of the body develops and one eye "migrates" to the other side of the head—either the left or the right, depending on the species. Changes occur also in the skeletal and digestive systems; adults have only one dorsal and one anal fin, both without spines. The underside of the flatfish is pale and the top is colored to match the environment; some species, especially the flounders, are able to change their pigmentationpigmentation,
name for the coloring matter found in certain plant and animal cells and for the color produced thereby. Pigmentation occurs in nearly all living organisms.
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. Flatfishes are divided into three groups: the soles, families Soleidae, Cynoglossidae, and Achiridae; and the flounders (including the halibuts and others), families Achiropsettidate, Bothidae, Citharidae, Paralichthyidae, Pleuronectidae, Samaridae, and Scophthalmidae, and the spiny turbots, family Psettodidae.

The Soles

The American soles, of which there are several Atlantic and one Pacific species, have small, close-set eyes and small, twisted mouths with few or no teeth. They prefer warm, shallow water with a sandy or muddy bottom and are generally too small and bony for food. The hogchoker, or broad sole, and the tonguefish, family Cynoglossidae, are most common. The European species Solea solea, a 2-ft (61-cm) flatfish found from the Mediterranean to the North Sea, is a valuable food fish, the source of filet of sole (in the United States filet of sole is usually flounder).

The Flounders

The flounders are much larger fishes, including the fluke (Paralichthys), the halibut (Hippoglossus), the dab (Limanda), and the plaice (Pleuronectes). The smooth flounder is found on muddy bottoms in cold, shallow northern waters. The winter flounder (Pseudopleuronectes americanus) is an important food and game fish, taken in large numbers by trawlers. Like other flounders it migrates in winter to deeper waters to breed. It belongs to the righteye flounder family, Pleuronectidae. Similar is the summer flounder (Paralichthys dentatus), of the large-tooth flounder family, Paralyichthyidae, called fluke by fishermen, common from Maine to the Carolinas. The closely related California flounder, or California halibut (P. californicus), is prized sport fish found off California that weighs up to 50 lb (23 kg). The starry flounder, more brightly colored than its drab relatives, is a common Pacific species found from mid-California N to Alaska and W to Asia. Flounders feed on worms, crustaceans, and other small bottom invertebrates.

The European plaice is an important food fish, as is the American plaice. The American plaice is common at depths of from 20 to 100 fathoms on muddy or sandy bottoms, where it feeds on sea urchins, sand dollars, and other bottom life and grows to 30 in. (76.2 cm) and 14 lb (6.4 kg).

The halibuts are the largest flatfishes and are of great commercial importance. The Atlantic and the Pacific halibuts, Hippoglossus hippoglossus and H. stenolepis, respectively, are very similar, with large mouths and sharp, strong teeth. They feed voraciously on other fish and are found in colder waters. The maximum weight of a halibut is 600 lb (270 kg), but the usual specimens caught offshore at 100 to 400 fathoms weigh from 20 to 100 lb (9–45 kg); the male is generally much smaller than the female.

The commercially valuable tribe of European flatfishes called turbots is represented in American waters by a single species, Scophthalmus aquosus, commonly called the windowpane flounder, found on the Atlantic coast from Maine to the Carolinas. It is much smaller than its European cousins, rarely weighing over 2 lb (.9 kg), whereas the European turbots may reach 30 lb (13.5 kg).


Flatfishes are classified in the phylum ChordataChordata
, phylum of animals having a notochord, or dorsal stiffening rod, as the chief internal skeletal support at some stage of their development. Most chordates are vertebrates (animals with backbones), but the phylum also includes some small marine invertebrate animals.
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, subphylum Vertebrata, class Actinopterygii, order Pleuronectiformes.

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(vertebrate zoology)
Any of a number of asymmetrical fishes which compose the order Pleuronectiformes; the body is laterally compressed, and both eyes are on the same side of the head.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.


any marine spiny-finned fish of the order Heterosomata, including the halibut, plaice, turbot, and sole, all of which (when adult) swim along the sea floor on one side of the body, which is highly compressed and has both eyes on the uppermost side
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
References in periodicals archive ?
Further experiments should include different combinations of vessel speed, sweep angle, and gear visibility to stimulate the run response in flatfishes before their approach to the mouth of a trawl.
The behaviour of flatfishes. In Flatfishes: biology and exploitation (R.
Observations of fin use in relation to feeding and resting behavior in flatfishes (Pleuronectiformes).
Course Start Start Start over Catch Date latitude longitude depth ground size Tow (m/d) ([degrees]) ([degrees]) (m) ([degrees]) (kg) 1 6/17 45.463 -51.871 82.3 162 2875 2 6/20 45.438 -52.219 73.2 20 1725 3 6/22 45.430 -51.871 80.5 270 2944 4 6/23 45.393 -51.175 69.5 344 2530 5 6/24 45.454 -51.283 69.5 142 2392 Percentage of flatfishes in catch Observations Yellowtail American Witch Number of Tow flounder plaice flounder yellowtail 1 86 14 44 2 92 8 38 3 84 15 1 27 4 92 8 46 5 90 10 35 Table 2 Detailed description of each categorical variable used in the analysis of video footage from 5 tows with a bottom trawl in June 2010 on the southern Grand Bank off eastern Newfoundland.
Seasonal distributions of larval flatfishes (Pleuronectiformes) on the continental shelf between Cape Cod, Massachusetts, and Cape Lookout, North Carolina, 1965-1966.
Total number of flatfishes, by species and average length, collected in 3 same-day trawls per month at Wylly Creek from December 2004 through December 2005 (DuBeck & Curran, 2007).
Physical factors such as temperature and salinity could affect the distribution and abundance of flatfishes in estuaries (9, 2, 26).
The fluctuations between yearly recruitment of flatfishes could be caused by their natural mortality due to food limitations or predation (27).
Gibson RN: Impact of habitat quality and quantity on the recruitment of juvenile flatfishes. Neth J Sea Res 32: 191-206, 1994.
Allen RL, and Baltz DM: Distribution and microhabitat use by flatfishes in a Louisiana estuary.
Stoner AW and Ottmar ML: Relationships between size-specific sediment preferences and burial capabilities in juveniles of two Alaska flatfishes. J Exp Mar Biol Ecol 282: 85-101, 2003.
Gibson RN: Behaviour and distribution of flatfishes. J Sea Res 37: 241-256, 1997.