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Winter flounder, Pseudopleuronectes americanus Pseudopleuronectes americanus.jpg
Winter flounder, Pseudopleuronectes americanus
Flowery flounder, Bothus mancus,
Bahia de la Chiva, at Hawaii Flounder hawaii.jpg
Flowery flounder, Bothus mancus,
Bahía de la Chiva, at Hawaii

Flounders are a group of flatfish species. They are demersal fish, found at the bottom of oceans around the world; some species will also enter estuaries.

Flatfish order of fishes

A flatfish is a member of the order Pleuronectiformes of ray-finned demersal fishes, also called the Heterosomata, sometimes classified as a suborder of Perciformes. In many species, both eyes lie on one side of the head, one or the other migrating through or around the head during development. Some species face their left sides upward, some face their right sides upward, and others face either side upward.

Demersal fish

Demersal fish live and feed on or near the bottom of seas or lakes. They occupy the sea floors and lake beds, which usually consist of mud, sand, gravel or rocks. In coastal waters they are found on or near the continental shelf, and in deep waters they are found on or near the continental slope or along the continental rise. They are not generally found in the deepest waters, such as abyssal depths or on the abyssal plain, but they can be found around seamounts and islands. The word demersal comes from the Latin demergere, which means to sink.

Estuary A partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea

An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea.



The name "flounder" is used for several only distantly related species, though all are in the suborder Pleuronectoidei (families Achiropsettidae, Bothidae, Pleuronectidae, Paralichthyidae, and Samaridae). Some of the better known species that are important in fisheries are:

Bothidae family of fishes

Lefteye flounders are a family, Bothidae, of flounders. They are called "lefteye flounders" because most species lie on the sea bottom on their right sides, with both eyes on their left sides. A helpful reminder when trying to recall the family name for this fish is that "Bothidae eyes are on the same side o' dey head." The family is also distinguished by the presence of spines on the snout and near the eyes.

Pleuronectidae family of flounders

Pleuronectidae, also known as righteye flounders, are a family of flounders. They are called "righteye flounders" because most species lie on the sea bottom on their left sides, with both eyes on their right sides. The Paralichthyidae are the opposite, with their eyes on the left side. A small number of species in Pleuronectidae can also have their eyes on the left side, notably the members of the genus Platichthys.

Paralichthyidae family of fishes

Large-tooth flounders or sand flounders are a family, Paralichthyidae, of flounders. The family contains 14 genera with a total of about 110 species. They lie on the sea bed on their right side; both eyes are always on the left side of the head, while the Pleuronectidae usually have their eyes on the right side of the head.

Gulf flounder species of fish

The Gulf flounder is a species of saltwater flounder.

<i>Paralichthys lethostigma</i> species of fish

Paralichthys lethostigma, the southern flounder, is a species of large-tooth flounders native to the eastern and gulf coasts of the United States. It is a popular sports fish and is the largest and most commercially valuable flounder in the western North Atlantic Ocean and Gulf of Mexico. It is a "left-eyed flounder", meaning the left side is pigmented and is the "up side".

Summer flounder species of fish

The summer flounder is a marine flatfish that is found in the Atlantic Ocean off the East Coast of the United States and Canada. It is especially abundant in waters from North Carolina to Massachusetts.

Eye migration

In its life cycle, an adult flounder has two eyes on one side of its head, and at hatching one eye is on each side of its head. One eye migrates to the other side of the body through a metamorphosis as it grows from larval to juvenile stage. As an adult, a flounder changes its habits and camouflages itself by lying on the bottom of the ocean floor as protection against predators. [1] As a result, the eyes are then on the side which faces up. The side to which the eyes migrate is dependent on the species type.

Metamorphosis profound change in body structure during the postembryonic development of an organism

Metamorphosis is a biological process by which an animal physically develops after birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation. Metamorphosis is iodothyronine-induced and an ancestral feature of all chordates. Some insects, fishes, amphibians, mollusks, crustaceans, cnidarians, echinoderms, and tunicates undergo metamorphosis, which is often accompanied by a change of nutrition source or behavior. Animals that go through metamorphosis are called metamorphoses. Animals can be divided into species that undergo complete metamorphosis ("holometaboly"), incomplete metamorphosis ("hemimetaboly"), or no metamorphosis ("ametaboly").

Camouflage concealment through color or pattern

Camouflage is the use of any combination of materials, coloration, or illumination for concealment, either by making animals or objects hard to see (crypsis), or by disguising them as something else (mimesis). Examples include the leopard's spotted coat, the battledress of a modern soldier, and the leaf-mimic katydid's wings. A third approach, motion dazzle, confuses the observer with a conspicuous pattern, making the object visible but momentarily harder to locate. The majority of camouflage methods aim for crypsis, often through a general resemblance to the background, high contrast disruptive coloration, eliminating shadow, and countershading. In the open ocean, where there is no background, the principal methods of camouflage are transparency, silvering, and countershading, while the ability to produce light is among other things used for counter-illumination on the undersides of cephalopods such as squid. Some animals, such as chameleons and octopuses, are capable of actively changing their skin pattern and colours, whether for camouflage or for signalling. It is possible that some plants use camouflage to evade being eaten by herbivores.


Flounders ambush their prey, feeding at soft muddy areas of the sea bottom, near bridge piles, docks and coral reefs.

A flounder's diet consists mainly of fish spawn, crustaceans, polychaetes and small fish. Flounder typically grow to a length of 22–60 centimeters (8.7–23.6 in), and as large as 95 centimeters (37 in). Their width is about half their length. Male Platichthys are known to display a pioneering spirit, and have been found up to 80 miles off the coast of northern Sardinia, sometimes with heavy encrustations of various species of barnacle.

Fluke, a type of flounder, are being farm raised in open water by Mariculture Technologies in Greenport, New York. [2]


A flounder blending into its environment Flounder camo md.jpg
A flounder blending into its environment

World stocks of large predatory fish and large ground fish, including sole and flounder, were estimated in 2003 to be only about 10% of pre-industrial levels, largely due to overfishing. Most overfishing is due to the extensive activities of the fishing industry. [3] [4] [5] [6] Current estimates suggest that approximately 30 million flounder (excluding sole) are alive in the world today. [ citation needed ] In the Gulf of Mexico, along the coast of Texas, research indicates the flounder population could be as low as 15 million due to heavy overfishing and industrial pollution.[ citation needed ]

According to Seafood Watch, Atlantic flounders and soles are currently on the list of seafood that sustainability-minded consumers should avoid. [7]

Related Research Articles

Swordfish species of fish

Swordfish, also known as broadbills in some countries, are large, highly migratory, predatory fish characterized by a long, flat bill. They are a popular sport fish of the billfish category, though elusive. Swordfish are elongated, round-bodied, and lose all teeth and scales by adulthood. These fish are found widely in tropical and temperate parts of the Atlantic, Pacific, and Indian Oceans, and can typically be found from near the surface to a depth of 550 m (1,800 ft). They commonly reach 3 m (9.8 ft) in length, and the maximum reported is 4.55 m (14.9 ft) in length and 650 kg (1,430 lb) in weight.

Overfishing the act whereby fish stocks are depleted to unacceptable levels, regardless of water body size

Overfishing is the removal of a species of fish from a body of water at a rate that the species cannot replenish in time, resulting in those species either becoming depleted or very underpopulated in that given area. Overfishing has spread all over the globe and has been present for centuries.

Hogchoker species of fish

The hogchoker is a small flatfish found along the Atlantic coast of North America, ranging from Massachusetts and Florida to Panama. They prefer brackish water, and are abundant in many bays and estuaries north of the Carolinas. It is a member of the American sole family Achiridae. They are usually brown to dark brown in color, and lighter on their "blind side". The overall body color is often broken by a series of spots and thin stripes, which can be lighter or darker than the main body color. The fins and tail have fringed edges helping hide the fish from its prey. They mainly feed on small aquatic insects and invertebrates. They are regarded as "trash fish" by recreational fishermen but were fed to pigs but they have rather bony bodies which were sometimes difficult for the pigs to swallow, hence the vernacular name.

California halibut species of fish

The California halibut or California flounder is a large-tooth flounder native to the waters of the Pacific Coast of North America from the Quillayute River in Washington to Magdalena Bay in Baja California. It feeds near shore and is free swimming. It typically weighs 6 to 30 pounds. It is much smaller than the larger and more northern-ranging Pacific halibut that can reach 300 pounds (140 kg).

Sole (fish) fish name belonging to several families

Sole is a fish belonging to several families. Generally speaking, they are members of the family Soleidae, but, outside Europe, the name sole is also applied to various other similar flatfish, especially other members of the sole suborder Soleoidei as well as members of the flounder family. In European cookery, there are several species which may be considered true soles, but the common or Dover sole Solea solea, often simply called the sole, is the most esteemed and most widely available.

Starry flounder species of fish

The starry flounder, also known as the grindstone, emerywheel and long-nosed flounder, is a common flatfish found around the margins of the North Pacific.

New Zealand sand flounder species of fish

The New Zealand sand flounder is a righteye flounder of the genus Rhombosolea, found around New Zealand in shallow waters down to depths of 100 m.

European flounder species of fish

The European flounder is a flatfish of European coastal waters from the White Sea in the north to the Mediterranean and the Black Sea in the south. It has been introduced into the United States and Canada accidentally through transport in ballast water. It is caught and used for human consumption.

<i>Platichthys</i> genus of fishes

Platichthys is a genus of flatfish native to the North Pacific and North Atlantic oceans. Despite being in the family Pleuronectidae, all three species in the genus Platichthys are often "lefteyed", i.e. they lie on the sea bottom on their right side, with both eyes on the left side.

Pacific sand sole species of fish

The Pacific sand sole, also known as simply sand sole, is a flatfish species inhabiting the northeastern Pacific waters where it lives on sandy bottoms. The only species in the genus, Psettichthys, it ranges from the Bering Sea to Northern California.

<i>Hippoglossina oblonga</i> species of fish

Hippoglossina oblonga, is a flatfish and member of the large-tooth flounder family Paralichthyidae. This species has been placed in the genus Paralichthys by some authorities.

Eyed flounder species of fish

The eyed flounder is a species of fish in the family Bothidae. The species is found on or near the sandy seabed in relatively shallow waters in the western Atlantic Ocean, the Caribbean Sea and the Gulf of Mexico.


  1. Fairchild, E.A. and Howell, W.H, E. A.; Howell, W. H. (2004). "Factors affecting the post-release survival of cultured juvenile Pseudopleuronectes americanus". Journal of Fish Biology. 65 (Supplementary A): 69–87. CiteSeerX . doi:10.1111/j.0022-1112.2004.00529.x.CS1 maint: Multiple names: authors list (link)
  2. Kreahling, Lorraine (17 November 1996). "Farming Fluke in Open Water". The New York Times . Retrieved 26 July 2017.
  3. Clover, Charles (2008). The End of the Line: How Overfishing is Changing the World and what We Eat. University of California Press. ISBN   978-0-520-25505-0. OCLC   67383509.
  4. Myers, R. A.; Worm, B. (2003). "Rapid worldwide depletion of predatory fish communities". Nature. 423 (6937): 280–283. doi:10.1038/nature01610. PMID   12748640.
  5. Dalton, Rex (2006). "Save the big fish: Targeting of larger fish makes populations prone to collapse". BioEd Online. Retrieved 26 March 2017.
  6. Hsieh, Chih-hao; Reiss, Christian S.; Hunter, John R.; Beddington, John R.; May, Robert M.; Sugihara, George (2006). "Fishing elevates variability in the abundance of exploited species". Nature. 443 (7113): 859–62. doi:10.1038/nature05232. PMID   17051218.
  7. "Monterey Bay Aquarium: Seafood Watch Program – All Seafood List". Monterey Bay Aquarium. Archived from the original on 6 July 2010. Retrieved 17 April 2008.