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~~ <br />observation Lead to the development of a downstream transport hypothesis (Tyus <br />et al 1982, Miller et al 19828). Although once debated (Holden and Wick 1982). <br />this hypothesis is now generally accepted (Haynes et aI 1984, Wick et al 1983, <br />USFWS 1988), and supported by laboratory experiments that confirmed active <br />downstream movement for 6 week and older Colorado squawfish young (Paulin et <br />al 1989). <br />Juveniles <br />Juvenile Colorado squawfish range from about 60 to 400 mm TL (Tyus et al <br />1982b), encompassing age-1, to about age-5 fish. Little is known about <br />smaller juveniles (size range 100-300 mm TL), because they are captured less <br />frequently than any other size. The downstream location of postlarval Colorado <br />squawfish indicates the need for long-distance upstream movement of juveniles <br />if the upstream areas are to be repopulated. Such movement probably occurs in <br />the late juvenile or early adult stage (subadult=300-500 mm TL), as suggested <br />by high concentrations of juveniles in the lower section of the mainstream <br />Green River, and highest concentrations of adults in upstream sections (Tyus <br />et al 1987). Fish collection data from the lower White and Yampa River tends <br />to support this hypothesis (Tyus 1986). This separation of life stages may aid <br />in reducing intraspecific predation by adults on the young. <br />DISTRIBUTION AND ABUNDANCE <br />Upper Colorado River <br />10 <br />