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Last modified
7/14/2009 5:01:47 PM
Creation date
5/20/2009 11:04:27 AM
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UCREFRP
UCREFRP Catalog Number
8162
Author
Osmundson, D. B., R. J. Ryel, M. E. Tucker, B. D. Burdick, W. R. Elmblad and T. E. Chart.
Title
Dispersal Patterns of Subadult and Adult Colorado Squawfish in the Upper Colorado River.
USFW Year
1998.
USFW - Doc Type
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Copyright Material
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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;
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