Pleuronectiformes
66 species
A flatfish is a member of the ray-finned demersal fish order Pleuronectiformes, 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.
Many important food fish are in this order, including the flounders, soles, turbot, plaice, and halibut. Some flatfish can camouflage themselves on the ocean floor.
Flatfishes are found in oceans worldwide, ranging from the Arctic, through the tropics, to Antarctica. Species diversity is centered in the Indo-West Pacific and declines following both latitudinal and longitudinal gradients away from the Indo-West Pacific. Most species are found in depths between 0 and 500 m (1,600 ft), but a few have been recorded from depths in excess of 1,500 m (4,900 ft). None have been confirmed from the abyssal or hadal zones. An observation of a flatfish from the Bathyscaphe Trieste at the bottom of the Mariana Trench at a depth of almost 11 km (36,000 ft) has been questioned by fish experts, and recent authorities do not recognize it as valid. Among the deepwater species, Symphurus thermophilus lives congregating around "ponds" of sulphur at hydrothermal vents on the seafloor. No other flatfish is known from hydrothermal vents. Many species will enter brackish or fresh water, and a smaller number of soles (families Achiridae and Soleidae) and tonguefish (Cynoglossidae) are entirely restricted to fresh water.
A flatfish is a member of the ray-finned demersal fish order Pleuronectiformes, 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.
Many important food fish are in this order, including the flounders, soles, turbot, plaice, and halibut. Some flatfish can camouflage themselves on the ocean floor.
Flatfishes are found in oceans worldwide, ranging from the Arctic, through the tropics, to Antarctica. Species diversity is centered in the Indo-West Pacific and declines following both latitudinal and longitudinal gradients away from the Indo-West Pacific. Most species are found in depths between 0 and 500 m (1,600 ft), but a few have been recorded from depths in excess of 1,500 m (4,900 ft). None have been confirmed from the abyssal or hadal zones. An observation of a flatfish from the Bathyscaphe Trieste at the bottom of the Mariana Trench at a depth of almost 11 km (36,000 ft) has been questioned by fish experts, and recent authorities do not recognize it as valid. Among the deepwater species, Symphurus thermophilus lives congregating around "ponds" of sulphur at hydrothermal vents on the seafloor. No other flatfish is known from hydrothermal vents. Many species will enter brackish or fresh water, and a smaller number of soles (families Achiridae and Soleidae) and tonguefish (Cynoglossidae) are entirely restricted to fresh water.
