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INTRODUCTION An essential part of determining of limiting factors for Colorado squawfish (Ptychocheilus Lucius) in the Yampa River is the characterization of habitat requirements of that species. There is limited existing information on Colorado squawfish habitat use or movement in the Yampa River during the low flows which occur during late summer. Previous studies mainly focused on spawning migrations or winter habitat use (Tyus and McAda 1984; Wick and Hawkins 1989). This study relates to the Green River Action Plan, Yampa River Elements 1.A.2., 1.AA.a.(3)(a)., and 1.B.2. of identifying base flow discharge needs of endangered fishes in the Yampa River. The goal of this study is to determine habitat use patterns of endangered fishes in the Yampa River during the lowest flow period of the year (i.e., August through October). The specific objectives of this study include: • monitor movements of Colorado squawfish, northern pike and channel catfish in the Yampa River during the low flow periods (August through October) • to determine the range of habitats occupied during the base flow periods. The specific objectives of this study were to monitor movements of Colorado squawfish using radio telemetry to determine: 1) the range of movement during the low flow period; 2) summer low flow habitat use; and 3) the distance Colorado squawfish moved from later summer into winter. In addition, northern pike and channel catfish were also radio implanted in the same locations and monitored during the monitoring of the Colorado squawfish movement. In addition to the determination of movement patterns, telemetry data will be used to compare sites occupied by Colorado squawfish during summer flow conditions to the availability of habitat during summer low flow habitat months. The availability of distinct habitat types will be determined in another portion of the study which measured channel cross sections and modeled hydraulics of various water levels to determine how habitat changes with flow. Study Area The study area extended from Cross Mountain Canyon to Craig, Colorado (Figure 1). The area which the radio tagged fish occupied was the reach from Craig, Colorado (RM 137) down to about 2 miles below Maybell bridge (RM 77) thereby defining the area for this study. The radio telemetry observation data was acquired within this limited reach. Colorado squawfish have been located in previous years within this reach (Tyus and McAda 1984; Wick et al. 1986, Wick and Hawkins 1989). Previous Studies on Colorado Squawfish Researchers have been studying movement and habitat use of Colorado squawfish since the mid 1970s. The focus of these previous research efforts have been either long range migration to determine spawning locations or intensive study of localized habitat use. Final Report - Colorado squawfish habitat Page 1 Miller Ecological Consultants, Inc. December 17, 1997