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Last modified
7/14/2009 5:02:33 PM
Creation date
5/22/2009 7:38:36 PM
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UCREFRP
UCREFRP Catalog Number
8159
Author
Trammell, M. and T. Chart.
Title
Aspinall Studies
USFW Year
1999.
USFW - Doc Type
Annual Assessment of Colorado Pikeminnow Larval Production in the Colorado River, Utah 1992-1996 \
Copyright Material
NO
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o Neither peak discharge nor runoff flows were con elated to duration of spawning <br />activity, however, peak discharge was negatively correlated to the duration of the drift, <br />(from the first to last day Colorado pikeminnow larvae were collected). <br />o The estimated onset of spawning occurred earlier at Moab than at Westwater in four <br />out of five years, supporting the existence of spawning between the sites. <br />• Objective 2) evaluate the effect of flows on relative abundance of drifting Colorado <br />pikeminnow larvae <br />o Total transport abundance was higher at Moab that at Westwater in four of the five <br />yeass of study, supporting the existence of spawning between the sites. <br />o The flow variables of peak discharge and average June flow were not linearly <br />correlated with catch rates and transport abundance of Colorado pikeminnow larvae. <br />However, transport abundance had a slight positive association with higher flows <br />during peak dischazge and with high June flows. <br />o Transport abundance was maximized during moderate to high flow years. <br />o High peak discharge resulted in a greater percentage of native species in the total <br />number of fish collected. Particularly in Westwater, the low water year of 1994 <br />showed a reduced percentage of native, and a corresponding increase in percentage of <br />non-native cyprinids. In the five yeass of study, the percentage of Colorado <br />pikeminnow in the drift was highest in the moderate to high water years. <br />• Objective 3) determine if relative abundance of larvae varies similarly with the relative <br />abundance of juveniles in the nursery habitats in the fall <br />o Colorado pikeminnow larval drift densities were not linearly correlated with young-of- <br />year densities in fall backwaters within reaches in all years. Drift densities at Loma or <br />Westwater were not related to fall year class strength in the Moab reach. <br />o Larval abundance was fairly indicative of juvenile abundance in years other than 1995. <br />In 1995, high larval abundance was followed by low juvenile abundance. <br />o Mean length of Colorado pikeminnow in the fall was negatively correlated with the <br />magnitude and duration of peak runoff flows. In 1995, high peak discharge and runoff <br />flows contributed to delayed spawning and decreased degree accumulation, resulting <br />in a shorter, less than optimum growing season. <br />o The greater mean length of Colorado pikeminnow in the fall in low water years was <br />positively correlated with increased overwinter survival. <br />o Colorado pikeminnow densities in fall backwaters were not lineazly correlated with <br />flow. The intermediate flow year of 1996 had the highest densities of young-of year <br />Colorado pikeminnow. <br />• Effect of flows on non-native cyprinid densities <br />o At Moab, non-native cyprinid drift density was not related to flow, with high and low <br />water yeass having both high and low drift densities. <br />21 <br />
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