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Last modified
7/14/2009 5:02:31 PM
Creation date
5/18/2009 12:06:30 AM
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UCREFRP
UCREFRP Catalog Number
7801
Author
Valdez, R. A.
Title
Synthesis of Winter Investigations of Endangered Fish in the Green River Below Flaming Gorge Dam.
USFW Year
1995.
USFW - Doc Type
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had distinct pools and persistent off-channel habitats (e.g., backwaters, embayments), while the Green <br />River was dominated by runs with few persistent off-channel habitats, and daily fluctuating flows. <br />Movement by fish was greatest during ice break-up, as observed in March in both rivers and <br />periodically throughout winter on the Green River, with fluctuating dam releases. Average net <br />movement of Yampa River fish in fall, 1987 (September through November) was 1.4 km (n=8, range <br />of 0.0-7.1 km), while net movement in spring (March-April, 1988} was much greater, with an average <br />of 10.5 km (n=10, range of 0.0-69.5 km). <br />Valdez and Masslich (1989) concluded that the majority of adult Colorado squawfish in the <br />Green River probably overwinter within reaches 3 to 5 km long. Wick and Hawkins (1989) reported <br />that during ice-covered periods, total range of movement of all radiotagged Colorado squawfish was <br />only 0.5 km, with individual fish showing seasonal, as well as annual, fidelity to specific fall and winter <br />sites by returning to the same area two consecutive years. <br />Although radiotagged fish remained in specific areas in winter, they were quite active within <br />those areas in both rivers. This local movement in the Green River was often restricted to a specific <br />habitat (e.g., eddy, backwater, run, etc.), in which an individual fish occupied one to several favorite <br />locations for varying periods of time. One Green River fish monitored for 24 hours occupied four <br />different locations within the same slackwater (#OR-4021). Although the fish moved over 50 m <br />during monitoring, net displacement from the original location was only 10 m (Figure 12). The fish <br />occupied the four locations five times for periods of about 2, 1, 4, S, and 9 hours. A second Green <br />River fish (#OR-6101), monitored for 24 hours, moved a total of 118 m, with net movement of only <br />10 m. Similarly, the Yampa River fish moved between several favorite spots within a habitat (e.g., <br />embayment, backwater, etc.), staying in a spot for several minutes to several hours before moving. <br />Like the Green River fish, the Yampa River fish repeated this pattern of movement, often occupying <br />the same spot more than once. <br />Local movement by Green River fish was characterized by rates of 15 to 23 m/hr, as normal <br />for overwintering adult Colorado squawfish, in the absence of fluctuating flows and ice. Average local <br />movement by five fish under stable ice was 29 m/hr. Although not significantly different from <br />movement in the absence of ice, greater movement under ice--particularly in shallow water-indicates <br />use of ice as cover. Yampa River fish were also observed in relatively shallow water in the presence <br />of surface ice. <br />22 <br />
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