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Last modified
8/11/2009 11:32:57 AM
Creation date
8/10/2009 5:03:10 PM
Metadata
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Template:
UCREFRP
UCREFRP Catalog Number
9456
Author
Van Steeter, M. M. and J. Pitlick.
Title
Aerial photograph/GIS Analysis and Field Studies of the 15 and 18 Mile Reach of the Colorado River.
USFW Year
1994.
USFW - Doc Type
Boulder.
Copyright Material
NO
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<br />. <br /> <br />1 <br /> <br />. <br /> <br />Introduction <br />Problem Statement <br />Surveys of the Colorado River near Grand Junction, Colorado show <br />that populations of Colorado squawfish (Ptychocheilus lucius) and <br />razorback sucker (Xyrauchen texanus) are small and continue to decline. A <br />potentially important factor in their decline is a reduction in the amount of <br />available habitat. The fish are most commonly found in habitats of <br />complex channel which may be affected by bank stabilizing activities and <br />regulation of the river flow (Osmundson and Kaeding, 1991; Li et al., 1987). <br />Areas with channel complexity provide important habitats for the <br />fish in both their adult and larval life stages. Adult fish apparently prefer <br />these areas because they provide a range of habitats for feeding, shelter, and <br />reproduction. Areas of complex channel contain areas of low velocity <br />water and backwaters which are also very important to the larval life stage <br />of the fish. After hatching, larvae drift downstream and collect in <br />backwaters. Backwaters provide both a warm and nutrient rich <br />environment for the growth of the larvae as well as refuge from predators <br />which cannot enter shallow areas of the backwater. The absence of this <br />habitat results in continued drift downstream, greater exposure to <br />predators, and slower growth rates due to lower temperatures and inferior <br />food sources (fyus and Karp, 1989; Holden, 1977; Kaeding and <br />Osmundson, 1988). <br />Most fish habitat is influenced by the magnitude of flows, therefore a <br />reduction in flows due to river regulation affects fish habitats. For <br />example, the bankfull discharge appears to control channel features, thus <br />changes in flow magnitude result in changes in the channel (Schumm, <br />1969). H flows are decreased for a significant period of time, the river <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br />
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