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Round whitefish
The round whitefish (''Prosopium cylindraceum'') is a freshwater species of fish that is found in lakes from Alaska to New England, including the Great Lakes. It has an olive-brown back with light silvery sides and underside and its length is generally between . They are bottom feeders, feeding mostly on invertebrates, such as crustaceans, insect larvae, and fish eggs. Some other fish species, like white sucker in turn eat their eggs. Lake trout, northern pike and burbot are natural predators. Other common names of the round whitefish are menominee, pilot fish, frost fish, round-fish, and menominee whitefish. The common name "round whitefish" is also sometimes used to describe ''Coregonus huntsmani'', a salmonid more commonly known as the Atlantic whitefish.
While it was once common, numbers have been decreasing in the last century due to a number of possible causes. The round whitefish is now protected in some states, such as New York, under the Endangered Species Act from harvest or possession. In Alaska, the whitefish is occasionally caught by anglers, but in general, the fish is not sought after, is rarely caught, since it is a bottom feeder; and the species is not protected.〔〔
==Description==
The whitefish is part of the salmon family, and the distinctive traits of this subfamily (in comparison to the rest of the salmon family) include larger scales, smaller mouth, weak or no teeth, and other internal characteristics.〔 The round whitefish is a cylindrical fish (hence cylindraceum) and is considered a deep-bodied fish. It is mostly silver in color with a few exceptions. Its back has a green tinge to its appearance with scales that range from sepia brown to bronze and are edged with black. Its lower fins can be various shades of amber, and its adipose fin is normally brown spotted.〔 The round whitefish has between 42-46 scales around its body, 22-24 scales around its caudal peduncle, and 83-96 scales in its lateral line. In addition, this species has 87-117 pyloric caeca, 59-63 vertebrae, and less than 20 gill rakers. The round whitefish is different than other whitefish by having one flap between the nostril openings (instead of two). It can grow up to 50 centimeters (cm) in length〔and typically grow in increments of 55-65 millimeters (mm) annually. Most of its growth takes place in its first five years of life.〔 Round-fish can live up to 12 years.〔
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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