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<br />3 <br /> <br />Job 8. <br /> <br />Title: <br /> <br />Colorado squawfish age and growth <br /> <br />Objectives: <br /> <br />1) to evaluate use of scales as a standard ageing method for Colorado <br />squawfish. <br />2) to validate the scale technique by use of other bony structures and <br />mark-recapture information. <br />3) to determine average individual growth rates and compare between <br />populations. <br />4) to determine the age composition of each population. <br />5) to compare rates of growth, size at maturity, and longevity in male and <br />female Colorado squawfish. <br /> <br />STUDY AREA <br /> <br />The river basins in the northwest corner of Colorado comprised the study <br />area within Colorado for most of the above jobs (Figure 1). Field sampling <br />for Jobs 1 and 2 included most of the Yampa River from Hayden downstream to <br />the Green River confluence, and the Colorado River from Palisade to Westwater <br />Canyon in Utah. Radiotracking in Job 3 was conducted on the Yampa River from <br />approximately river kilometer (RK) 275 to RK 0 (confluence). Field sampling <br />in 1980-1984 for Job 5 was conducted on the Yampa River from Cross Mountain <br />Canyon (RK 90) to RK O. Standardized monitoring in Job 6 included select <br />reaches on the Yampa, White, and Colorado rivers for spring sampling; and <br />select reaches on the Colorado River only for fall sampling. Scale samples <br />from Colorado squawfish used in Job 8 were the result of field collected fish <br />taken throughout their range in the Upper Colorado River Basin. The age- <br />growth data was organized by sub-basin, including the Yampa, White, and <br />Colorado rivers within Colorado, and the Green River in Utah. <br /> <br />METHODS <br /> <br />Job l: <br /> <br />Gamefish species life history data, and <br /> <br />Job 2: <br /> <br />Gamefish predation upon endangered fishes. <br /> <br />Yampa River <br /> <br />Intensive sampling using electrofishing, netting, seining and angling were <br />conducted in four distinct reaches of the river during May through November <br />1990. Study area reaches (Figure 1) included Lily Park-Deerlodge Park (RK 72- <br />90) , Maybell-Sunbeam (RK 93-143), Juniper Springs (RK 145-188), and Hayden- <br />Craig (RK 188-274). Fish samples served to acquire data on abundance, <br />distribution, reproductive success, age/size structure, and food habits of <br />riverine populations of non-native, non-salmonid gamefish species present. <br />