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flowing between 2500 and 5000 cfs, which corresponds with the late summer period when most YOY <br />chubs (75% of the total catch) were collected. The range of sampled flows however, was 2030 cfs (29 <br />July 94) to 40,000 cfs (22 June 95). <br />The three sampled strata varied greatly geomorphically. As would be expected habitat <br />availability varied as well. All backwaters were sampled throughout the study area, many of which <br />reformed from year to year. Backwaters were most common in the areas above and below the canyon. <br />As a result, a greater proportion of sampling effort was directed to less stable habitats (shorelines areas <br />and embayments) within Westwater Canyon (Table 6). <br />Table 6. Distribution of sampling effort by habitat types in the three sampling sub-reaches. <br />Westwater Canyon, Colorado River; 1992 -1996. Results of sampling in July and August _ <br />1992, 1994, and 1996. An additional, early September sampling effort was incorporated in <br />the 1993 and 1995 data sets. See Appendix Table 2 for habitat type descriptions. <br />HABITAT TYPES ABOVE CANYON <br />AREA SAMPLED = 3750 m' WESTWATER <br />AREA SAMPLED = 3842.Sm' BELOW CANYON <br />AREA SAMPLED =19°7 m' <br />BACKWATER 83.2% 29.7% 57.1 <br />SHORELINE 0.8 39.3 11.6 <br />EMBAYMENT - 20.0 5.8 <br />SIDE CHANNEL 12.4 5.3 7.0 <br />POOL 1.6 1.4 0.7 <br />ISOLATED POOL 2.0 2.0 8.8 <br />FLOODED TRIB - 2.3 15.0 <br />The analysis that follows has been presented by study sub-reach. In each sub-reach, low velocity <br />habitat availability is addressed and selection by YOY chubs within that set of habitats sampled is <br />described. Finally, relationships between the more frequently-used habitats and flows at the time of <br />sampling and antecedent spring flows are presented. Analyses of habitat use and preference as well as <br />nursery habitat /flow relationships have been relegated to the July and August data. As mentioned <br />earlier, YOY chubs habitat preference /behavior appeared to shift once they reached 40-50 mm TL <br />(typically sometime in September). <br />Above the Canvon (RK 204-199.41 <br />Backwaters were relatively abundant above the canyon. There were nine distinct backwaters that <br />were sampled on several occasions throughout the study. Specific backwater habitat availability was <br />dependent on river stage, but as many as six of the nine could be present at one time as was the case on <br />22 Aug 1995. As a result, the majority of seining effort (83.2% of the total area sampled (3749.5 m2 )) <br />above the canyon was expended in backwater habitats (see Table 6). Secondary channels were the only <br />other frequently (12.4%) sampled habitat followed by a variety of types which in the aggregate <br />comprised the remaining 5%. <br />A multinomial analysis of habitats (by type) used by YOY chubs indicated there was no <br />preference (p=.66) at the presence/absence level of detection (Table 7). YOY chubs were found in all <br />9 <br />