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.
Larval flounder are born with one eye on each side of their head, but as they grow from the larval to juvenile stage through metamorphosis, one eye migrates to the other side of the body. As a result, both eyes are then on the side which faces up. The side to which the eyes migrate is dependent on the species type. As an adult, a flounder changes its habits and camouflages itself by lying on the bottom of the ocean floor as protection against predators.
A flounder's diet consists mainly of fish spawn, crustaceans, polychaetes and small fish. Flounder typically grow to a length of 2260 centimeters (8.723.6 in), and as large as 95 centimeters (37 in). Their width is about half their length. Male Platichthys have been found up to 130 km (80 mi) off the coast of northern Sardinia, sometimes with heavy encrustations of various species of barnacle.
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. Current estimates suggest that approximately 30 million flounder (excluding sole) are alive in the world today. 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.