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Last modified
7/14/2009 5:02:37 PM
Creation date
5/24/2009 7:11:02 AM
Metadata
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UCREFRP
UCREFRP Catalog Number
9673
Author
Tyus, H. M. and G. B. Haines.
Title
Distribution, Habitat Use, and Growth of Young Colorado Squawfish in the Green River Basin, Colorado and Utah - Preliminary Report.
USFW Year
n.d.
USFW - Doc Type
Vernal, UT.
Copyright Material
NO
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. Habitat use.-The timiny of spawning, and thus hatching, is critical to <br />larval survival. Spawning occurs during the period of declining flows <br />following spring peak runoff and increasing temperatures, and it occurs <br />earlier in low flow years and later in high flow years. This temporal <br />adaptation (mid-summer spawning associated with decl-fining flows) is <br />associated with the reproductive strategy of the species (Tyus 1986), <br />whereby the length of exposure of eggs and larvae to lethal cold <br />temperatures of spring and to predation is reduced, and the short growth <br />period is balanced by movement of fish into backwater nursery habitat. <br />Backwaters (shallow ephemeral shoreline embayments) were heavily utilized <br />as nursery habitats by young Colorado squawfish in the Green River, as <br />previously noted by Holden and Stalnaker (1975) and Tyus et. al. (1982). <br />These backwaters were created by gradually decreasing summer flows <br />following spring runoff (snowmelt). <br />The Colorado squawfish reproductive strategy that has evolved over <br />thousands of years may no longer be adaptive for the Green River. <br />Increased predation by introduced non-native fishes and altered flow <br />regimes from Flaming Gorge Dam have produced an environment for which the <br />Colorado squawfish is ill-suited. Reduced standing crop and growth of <br />young fish brought about by high summer flows was viewed as a significant <br />impact that could .preclude management actions (Rose and Hamill 1988). <br />However, changes in water management to flow regimes more optimal to <br />young Colorado squawfish could overcome this problem (B.D. Williams, U.S. <br />Bureau of Reclamation, personal communication). We believe the mainstream <br />Green River can be managed as a Colorado squawfish nursery area by <br />15 <br />
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