flat·​fish ˈflat-ˌfish How to pronounce flatfish (audio)
: any of an order (Pleuronectiformes) of marine typically bottom-dwelling bony fishes (such as the halibuts, flounders, turbots, and soles) that as adults swim on one side of the laterally compressed body and have both eyes on the upper side

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There are about 600 species of flatfish, which have oval, flattened, bony bodies and are found from tropical to cold waters. Flounder and turbot are two examples. Most flatfish species live at moderate depths along the continental shelf, but some enter or live permanently in freshwater. Flatfishes are carnivorous bottom-dwellers that habitually rest on one side. Both eyes are on one side of the head. The side of the fish with eyes (uppermost as it lies on the bottom) is pigmented, but the lower side is normally white. Some flatfish change color to blend with their surroundings. Species vary from 4 in (10 cm) to 7 ft (2 m) long, and some (for example, the Atlantic halibut) may weigh as much as 720 lb (325 kg).

Examples of flatfish in a Sentence

Recent Examples on the Web The men nonetheless spotted a flatfish, which instantly answered an old question: Did the sea’s greatest depths harbor life or a bare desert? William J. Broad, New York Times, 18 Nov. 2023 For the right diners, this will be an exciting chance to learn about flatfish anatomy. Pete Wells, New York Times, 19 Sep. 2023 There’s anew press release out about a fossil flatfish called Heteronectes, which is oddly half-committed. Ed Yong, Discover Magazine, 26 June 2012 The council action followed several days of often emotional testimony in an ongoing fisheries battle over the scope of the trawlers’ catch of a revered flatfish — found off the West Coast, British Columbia and Alaska — that surveys indicate have largely been in decline during the past 15 years. Hal Bernton, Anchorage Daily News, 14 Dec. 2021 What is a flatfish? National Geographic, 11 June 2020 In the scallop fishery in the Irish Sea, use of Pisces lights reduced bycatch of haddock by 47% and flatfish by 25% with no effects on the take of scallops. Anchorage Daily News, 16 Aug. 2021 Within a population of Senegalese sole, a typically non-aggressive flatfish, for instance, researchers observed dominant behaviors more often in areas where territory or resources were scarce. Sarah Jay, Discover Magazine, 31 Jan. 2022 However, other kinds of flatfish were not significantly impacted. Jennifer Ball, Discover Magazine, 1 Apr. 2022

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'flatfish.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History

First Known Use

1710, in the meaning defined above

Time Traveler
The first known use of flatfish was in 1710

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Cite this Entry

“Flatfish.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/flatfish. Accessed 18 Apr. 2024.

Kids Definition


flat·​fish -ˌfish How to pronounce flatfish (audio)
: any of a group of marine fishes (as halibuts, flounders, or soles) that as adults swim on one side of the flattened body and have both eyes on the upper side

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