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948 <br />OSMUNDSON ET AL. <br /> <br />a0' <br />1 <br />FIGURE 4.-Movement of Colorado squawfish PIT-tagged in the upper reach of the Colorado River. Arrow origins <br />represent capture location; arrow points represent location of next capture. Consecutive captures were at least 1 year <br />apart; only movements greater than 10 km are shown. <br />Mean CPUE of adults 500 mm and longer was <br />0.13 (SE = 0.09; N = 49) in the lower reach and <br />0.46 (SE = 0.09; N = 114) in the upper reach. <br />By 1993, adult demographics were quite differ- <br />ent. Adult Colorado squawfish 500 rum and longer <br />were captured in stratum 1 (17 fish) and stratum <br />2 (2 fish) for the first time during the study, and <br />CPUE of individuals 500 mm and longer increased <br />to 0.20 per net (SE = 0.04; N = 115 net sets). In <br />the upper reach, 1993 CPUE of adults was 0.57 <br />(SE = 0.10; N = 115). In 1994, catch rates were <br />generally similar to those of 1993 in both reaches. <br />This increase in adult CPUE from 1991 to 1993 <br />coincided with the recruitment of 2-3 strong year- <br />classes produced during the mid-1980s (see Os- <br />mundson and Burnham 1998). <br />Movements <br />Of Colorado squawfish initially captured and <br />tagged in the upper reach, 69 were recaptured at <br />least once in a subsequent year, and some were <br />recaptured in two or more subsequent years. In- <br />cluding multiple captures of the same fish, there <br />were 92 recaptures during 1991-1995. Of these, <br />16 (17%) were located farther than 10 km from <br />the previous capture site. Twelve of these 16 dis- <br />placements were directed upstream (Figure 4), <br />three were directed downstream, and one was di- <br />rected both downstream and upstream (this fish <br />moved down the Colorado River and up the lower <br />Gunnison River). Of movements entirely within <br />the Colorado River, the portion of displacements <br />directed upstream was higher (test of proportions, <br />P = 0.0098) than predicted if direction was ran- <br />dom (50%), though mean distance moved up- <br />stream was not significantly different than that <br />moved downstream (P = 0.359). None of the fish <br />captured in the upper reach during the study period <br />was later recaptured in the lower reach. <br />Of fish initially captured in the lower reach, 37 <br />were recaptured in one or more subsequent years, <br />totaling 43 recaptures during 1992-1995. Of the <br />43 recaptures, 25 (58%) were located farther than <br />10 km from the previous capture site. Seventeen <br />(68%) of these long-distance displacements were <br />directed upstream (Figure 5); this proportion was <br />not significantly different than if direction was ran- <br />dom (P = 0.086). However, when data from those <br />moving more than 25 km (N = 23) were analyzed, <br />the percent of fish having moved upstream (74%) <br />was significantly different than 50% (P = 0.037). <br />Also, the mean distance of movements (>10 km) <br />directed upstream (108.2 km, SE = 16.5) was sig- <br />nificantly greater (t-test, P = 0.0005) than the <br />mean distance of those directed downstream (35.1 <br />km, SE = 6.9). <br />Many fish captured in the lower reach were later <br />recaptured in the upper reach sometime during the <br />5-year period: 11 of 25 movements farther than 10 <br />km (44%) were from the lower reach to the upper <br />reach. Though sample sizes were small and sample <br />efforts in 1995 were different from those during <br />1991-1994, the proportion of fish initially cap- <br />tured in the lower reach and recaptured in the upper <br />reach increased from 1992 through 1995. In 1992, <br />no recaptures of lower-reach fish occurred in the <br />upper reach (0 of 1 recapture); in 1993, 2 of 14 <br />such recaptures (14%) occurred in the upper reach;