9524

• UCREFRP Catalog Number: 9524
• Author: Kitcheyan, C. D. and e. al.
• Title: Evaluation of the Effects of Stage Fluctuations on Overwinter Survival and Movement of Young Colorado Pikeminnow in the Green River, Utah, 1999-2002.
• USFW Year: 2004.
• USFW - Doc Type: Denver.
• Copyright Material: NO

backwater from which they re-inhabit once the stage recedes. Other riverine fish have been documented
to behave similarly in response to ice formation, which reduces physical space and changes depth and
velocity. Atlantic salmon (Salmo salar) young-of-the-year redistributed to find suitable depth and
velocity habitats (Whalen et al. 1999). Whalen et al. (1999) found that young Atlantic salmon exhibited a
combination of strategies, first movement and then fidelity, suggesting an integration of strategies for
winter survival.
Winter survival of small fish is related to their ability to accumulate energy reserves (Oliver et al.
1979; Shuter and Post 1990). Small fish are at a disadvantage because basal metabolism increases as size
decreases, but there is no corresponding increase in energy storage capacity. Mortality of young
Colorado pikeminnow during winter has been attributed to exhaustion of lipid reserves (Thompson et al.
1991). Body weight and condition decline faster when fish activity increases, because energetic reserves
must be used to offset the higher metabolic rate. Bioenergetics model predictions suggest that overwinter
survival of age-0 Colorado pikeminnow may be negatively affected if fish activity increases in response
to human-induced changes in the environment. When activity rates were at low and moderate levels
(s0.5 bl/s), age-0 fish survived to the end of the winter period. But when activity was at a high level (1.0
bl/s), fish did not survive to the end of the winter period regardless of their size.
The objective of this investigation was to evaluate the effects of winter operations (i.e. flow
fluctuations) of Flaming Gorge Dam on the distribution, nursery habitat, and overwinter survival of age-0
Colorado pikeminnow. The magnitude of daily flow fluctuations in this study produced a stage change of
<0.1 m at the Jensen gage and <0.01 m at the Ouray bridge. These flow fluctuations did not directly alter
physical morphology of backwaters in the Ouray complex. Ice jams increased stage elevation by 0.75 to
1.50 m which transformed many backwater habitats into flow-through areas. Under these conditions,
overwinter movement (between autumn and spring sampling) of young-of-year Colorado pikeminnow
was about 3 miles or less. Mark-recapture population estimates were hampered by relatively low
Xvll