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backwaters at the Walter Walker Wildlife Area (Stratum 6), two sites across the river from one another in the 15-mile reach (Stratum 7), and Knowles Canyon (Stratum 5). Of those Colorado squawfish initially captured and tagged in the upper reach, 16% were later located > 10 km from the previous capture site. Of these movements, 80% were directed upstream. None of the fish located in the upper reach during the study period were later recaptured in the lower reach. Of those fish tagged in the lower reach, 58% were later located > 10 km from the previous site; 68% of these displacements were directed upstream. Over the five-year period, 44% of movements > 10 km were from the lower reach to the upper reach, and the proportion of these between-reach movements increased each year. Distance moved was inversely related to fish size, i.e., distance moved decreased with increased fish size. Displacement of fish < 550 mm TL averaged 33.6 km; for those > 550 mm TL, average displacement was only 7.5 km. The smallest fish we documented moving from the lower to the upper reach was no longer than 449 nun, and the largest fish was at least 570 mm long. Movement of young adult Colorado squawfish was likely a response to their changing food requirements as they grew and matured. A net shift in abundance to upstream reaches was probably because upstream movements were rewarded with greater food availability. Two lines of evidence supported this hypothesis: 1) Catch rates of roundtail chub (Gila robusta) and bluehead (Catostomus discobolus) and flannelmouth sucker (C latipinnis), likely prey of adult Colorado squawfish, were significantly higher in the upper reach than in the lower reach, and 2) body condition of Colorado squawfish decreased with fish size in the lower reach but increased with fish size in the upper reach. Our results suggest that young Colorado squawfish move more than older ones and that upon arrival to the upper reach they move less. Evidently, older fish establish home feeding ranges in areas they have found to be most productive and have little need for further exploratory movements. The reach upstream of Westwater Canyon evidently provides the best adult feeding opportunities in the upper Colorado River. If reproduction and recruitment rates, currently limiting Colorado squawfish numbers in the Colorado River, can be increased, improved forage availability in existing reaches and passage to historic reaches would help provide for an expanding adult population. B-vi