The flounders are much larger fishes, including the fluke ( Paralichthys ), the halibut ( Hippoglossus ), the dab ( Limanda ), and the plaice ( Pleuronectes ). The smooth flounder is found on muddy bottoms in cold, shallow northern waters. The southern, or winter, flounder ( Pseudopleuronectes americanus ) is an important food and game fish, taken in large numbers by trawlers. Like other flounders it migrates in winter to deeper waters to breed. It belongs to the righteye flounder family, Pleuronectidae. Similar is the summer flounder ( Paralichthys dentatus ), of the lefteye flounder family, Bothidae, called fluke by fishermen, common from Maine to the Carolinas. The starry flounder, more brightly colored than its drab relatives, is a common Pacific species found from mid-California N to Alaska and W to Asia. Flounders feed on worms, crustaceans, and other small bottom invertebrates.
The European plaice is an important food fish, as is the American plaice, or sand dab, of which 3,000 tons are taken annually. The American plaice is common at depths of from 20 to 100 fathoms on muddy or sandy bottoms, where it feeds on sea urchins, sand dollars, and other bottom life and grows to 30 in. (76.2 cm) and 14 lb (6.4 kg).
The halibuts are the largest flatfishes and are of great commercial importance. The Atlantic and the Pacific halibuts, Hippoglossus hippoglossus and H. stenolepis, respectively, are very similar, with large mouths and sharp, strong teeth. They feed voraciously on other fish and are found in colder waters. The maximum weight of a halibut is 600 lb (270 kg), but the usual specimens caught offshore at 100 to 400 fathoms weigh from 20 to 100 lb (9–45 kg); the male is generally much smaller than the female. The California halibut, a smaller species (up to 60 lb/27 kg), is found S of San Francisco.
The commercially valuable tribe of European flatfishes called turbots is represented in American waters by a single species, Psetta maxima, commonly called the window pane, found on the Atlantic coast from Maine to the Carolinas. It is much smaller than its European cousins, rarely weighing over 2 lb (.9 kg), whereas the European turbots may reach 30 lb (13.5 kg).