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4 <br />METHODS AND MATERIALS <br />Scale Coll--, <br />Scales of Colorado squawfish were removed using methods described by <br />Carlson et al (1979)• Scales were taken between the years 1964 and 1966 from <br />Colorado squawfish of the Green River. Scales from Colorado squawfish of the <br />Colorado River were removed between 1976 and 1978. Collections of Colorado <br />squawfish scales from the Yampa River occured during 1982. After scale removal, <br />the scale was placed in a scale envelope for later analysis. <br />Scale Analysis <br />Scales were removed from the envelope at t..e laboratory, cleaned of extraneous <br />material and mounted between two slides. Scales were analyzed using a scale <br />enlarger, supplied by the Department of Fishery and Wildlife Biology. Scales <br />were measured along the anterior field from the focus to each annulus and also <br />to the edge. If annuli could not be determined from the anterior field, a 45 <br />degree angle measurement from the focus was used. Anterior field annuli then <br />could be determined by following a circulus from the diagonal field. All <br />regenerated scales were discarded. Measurements of scale radius and annuli <br />were used to backcalculate lengths using methods described by Everhart and <br />Youngs (1981). Colorado squawfish Age I+ to V+ were from Vaniceks data (1967) <br />of the Green River. Age VI+ fish and older were from the Yampa River. Back- <br />calculated lengths were used to determine relative growth rates of Colorado <br />squawfish using methods described by Everhart and Youngs (1981). Annuli were <br />counted for each scale to determine the fish's age and also to determine the <br />age composition of the Colorado squawfish. United States Geological Survey <br />flow and temperature data from the Yampa River was used to compare growth rates