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542 PAUKERT ET AL. fish moved throughout Grand Canyon. Two fish moved to and from the main stem near rkm 72 and the LCR (rkm 124) within 1 year, and five fish moved to and from Havasu Creek (Am 278) and the LCR with the period between capture and recapture (Table 1) ranging from 2 to 5 years. Proportionally fewer large fish exhibited restricted distribution than small fish. Only 76.5% of fish 300 mm or larger exhibited restricted distribution compared with 93.5% of fish 200-299 mm, and 98.7% of fish smaller than 200 mm (,'ez = 881; df = 2; P < 0.001). Odds ratios revealed that small fish were 23 times more likely to exhibit a restricted distribution compared with large fish, and five times more likely compared with medium-sized fish. Of the fish that exhibited a restricted distribution, mean distance between capture and recapture was typically lower for smaller fish. Humpback chub 300 mm or larger had a longer displacement between capture and recapture in the main-stem Colorado River (F = 4.39; df = 2, 352; P = 0.013) and the LCR (F = 396, df = 2, 9,584, P < 0.001; Figure 3). The percentage of fish exhibiting restricted distribu- tion did differ by time at liberty (x2 = 592; df = 7; P < 0.0001), but it was never less than 71% (for fish at liberty 5-10 years; N = 666). The percentage of fish exhibiting restricted distribution was greater than 90% for fish at liberty 14-30 d (N = 1,554), 31-90 d (N = 3,283, and more than 10 years (N = 29). When we considered the LCR and LCR inflow as one river reach, the proportion of fish that exhibited restricted distribu- tion increased to 100% for fish at liberty 14-30 d, 31- 90 d, and more than 5 years, and never was below 99.3%. Discussion Humpback chub showed restricted distribution within the Colorado River in Grand Canyon regardless of the spatial and temporal scale analyzed. Previous studies at shorter temporal scales demonstrated that humpback chub may remain in the same areas during spawning (Douglas and Marsh 1996; Gorman and Stone 1999), and other studies have suggested that this may occur annually as well (Keading et al. 1990; Valdez and Ryel 1995; Gorman and Stone 1999). Other large-river fishes have also shown substantial migrations to the same areas (Pellett et al. 1998; Stancill et al. 2002) and it has been suggested that this may not differ even to 5 years (Hay et al. 2001). Our study even found that fish at liberty over 10 (main-stem Colorado River) to 12 (LCR) years were recaptured near their same capture location. Other southwestern desert fishes (e.g., Colorado pikeminnow) have shown substantial migrations and a fidelity to spawning locations across long (up to 10-year) temporal scales (Tyus 1991), but others (e.g., razorback suckers) may move among several spawning locations over 3 years (Modde and Irving 1998), suggesting that some fish may not imprint to specific spawning locations. We could not confirm that all fish exhibiting restricted distribution remained in the same area between capture and recapture. Localized movements of adult humpback chub within the LCR have been documented (Douglas and Marsh 1996; Gorman and Stone 1999), and some of these fish may remain in the LCR all year (Douglas and Marsh 1996). However, these resident LCR fish were typically smaller than 300 mm (Gorman and Stone 1999), likely explaining why this study found increased fidelity of small (<200-mm) fish. Our study suggests that the most movement between rivers occurred at the confluence area (LCR inflow) of the LCR and main-stem Colorado River. This is not unusual, and it has been suggested that these fish are part of the same population (Kaeding and Zimmerman 1983; Douglas and Marsh 1996; Valdez and Hoffnagle 1999; Meretsky et al. 2000). However, there were a few humpback chub that moved at least 52 km upstream and 154 km downstream of the LCR confluence, suggesting that the LCR population does extend to a large part of the Colorado River and that limited movement may occur throughout Grand Canyon. Scale can have important influences on the manage- ment and conservation of fishes (Fausch and Young 1995; Hay et al. 2001). Since short-term tagging studies may miss important information relating to distribution and movement (Hay et al. 2001), a longer term evaluation of tag recaptures is necessary for a more complete understanding of distribution and movement in fishes. Our study involved 12 years of recaptures of over 7,000 individual fish. The de- termination of whether fish remained in the same area throughout the year or returned to the same area could not be evaluated in this study. However, the larger temporal scale suggests that restricted movement exists over longer periods of time. Distribution and move- ment of humpback chub in Grand Canyon appear to be primarily restricted to the LCR and LCR inflow area and is in contrast to other southwestem river fishes that may move long distances to meet their life history requirements. There appears to be little to no humpback chub reproduction or recruitment occurring in the main-stem Colorado River, probably because of the regulated, stenothermic environment, the invasion by nonnatives in the main stem (Clarkson and Childs 2000), and the fact that the humpback chub population in Grand Canyon is focused in and around the LCR. Manage- ment and monitoring of the humpback chub population