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<br />. <br /> <br />. <br /> <br />. <br /> <br />ABSTRACT OF THESIS <br />AGE AND GROWTH OF COLORADO SQUAWFISH <br />FROM THE UPPER COLORADO RIVER BASIN, 1978-1990. <br /> <br />. <br /> <br />Tagging records were examined for 2176 Colorado squawfish <br />Ptychocheilus lucius collected from the Colorado, Green, White, Vampa, and <br />tributary rivers. Length-frequency distribution modal range was 500-600 mm <br />total length. Weight-length relationships were established for fish from each of <br />the four primary rivers. Relative condition was greatest in spring and fall and <br />lowest in summer. A body-length to scale-radius relationship was developed <br />from 336 Colorado squawfish scales. Scales were aged and length at previous <br />annuli estimated using the Fraser-Lee method. First annulus was not observed <br />and may not form on most Colorado squawfish due to small size of fish at first <br />winter. After adjusting for the missing annulus, scales were suitable for ageing <br />Colorado squawfish up to 10 years old. Older ages were obtained but not <br />validated. Oldest fish was an 18-year-old from the Vampa River. Estimated <br />ages up to 10 years were validated with two 1 O-year -old stocked Colorado <br />squawfish aged correctly at recapture. Additional validation of older fish with <br />tagged and recaptured fish was partially successful. Relative growth calculated <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />iii <br /> <br />. <br />