Comprehensive Description

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Comprehensive Description

Most of the several hundred fishes known as flounders are in either the Pleuronectidae (right-eyed flounders, around 100 species, many of which have a dorsal branch near the front of the lateral line that runs along the base of the dorsal fin) or the Bothidae (left-eyed flounders, which lack a dorsal branch to the lateral line, although it may be forked above the upper eye). Most pleuronectids live in temperate to cold waters; tropical species generally occur in deeper water. Pleuronectids include several commercially important species in the Arctic, Atlantic, and Pacific Oceans. These include, among others, two of the largest of all bony fishes, the large-mouthed Pacific Halibut (Hippoglossus stenolepis) and Atlantic Halibut (Hippoglossus hippoglossus), which historically grew to at least 2.5 meters and 320 kg (although as a result of intensive fishing specimens now rarely reach even half this size); the American Plaice (Hippoglossoides platessoides); flounders such as the Winter Flounder (Pseudopleuronectes americanus); and the Petrale Sole (Eopsetta jordani). A very large female halibut may be 30 years old and can produce over 2 million small eggs. Because of the eggs' neutral buoyancy, the eggs typically float in midwater, sinking gradually as development proceeds. (Eschmeyer and Herald 1983; Robins and Ray 1986; Chapleau and Amaoka 1995)

Adult pleuronectids have the eyes and color pattern on the right side of the body. Like the hatchlings of other flatfishes, at an early age pleuronectid larvae begin to lean to one side as one eye (the left eye in the case of pleuronectids) migrates across the crown to a position beside the other eye. In addition, the front of the skull twists, bringing the jaws into a sideways position, and the side of the fish that faces down when it is in a resting position turns whitish. (Chapleau and Amaoka 1995)


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© Shapiro, Leo

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