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<br />. <br /> <br />The Colorado squawfish was very common at one time, abundant enough <br />to be pitchforked out of irrigation canals in Arizona (Miller 1961). <br />Presently it is extinct in the Colorado system below Glen Canyon Dam <br />(Minckley 1973), the Green River above Flaming Gorge Dam (Baxter and <br />Simon 1970), and the San Juan River in New Mexico (Figure 1). The Green <br />River system of Colorado and Utah, including the Yampa and White rivers, <br />and the mainstem Colorado River below Grand Junction, Colorado, harbor <br />the last remaining populations. One juvenile was recently captured in <br />the San Juan River of Utah (VTN 1978). Reproductive success is highest <br />in the Green River (Holden and Stalnaker 1975a). <br />This paper will discuss what is presently known concerning Colorado <br />squawfish life history, and the chances for survival of this unique ani- <br />mal. Much of the recent work on this species has not been formally <br />published but is contained in readily available reports from various <br />agenc i es and pr i vate concerns. An extreme 1 y i ntens i ve study on th is <br />species is presently being conducted by the U.S. Fish and Wildlife <br />Service (USFWS). Ed Wick has been working with this study and some of <br />his general observations are included in this report. More detailed <br />data should be available in 1982 when the USFWS completes their study. <br /> <br />Age and Growth <br /> <br /> <br />Vanicek and Kramer (1969) provide the most indepth information on <br />age and growth of Colorado squawfish. Their mean calculated total <br />lengths for 658 fish from the upper Green River showed that young <br /> <br />2 <br />