8170

• UCREFRP Catalog Number: 8170
• Author: Trammell, M. A., K. D. Christopherson, C. L. Rakowski, J. C. Schmidt, K. S. Day, C. Crosby and T. E. Chart.
• Title: Flaming Gorge Studies
• USFW Year: 1999.
• USFW - Doc Type: Assessment of Colorado Pikeminnow Nursery Habitat in the Green River.
• Copyright Material: NO

INTRODUCTION
Nursery habitat availability is considered a bottleneck to successful recruitment of the
endangered Colorado pikeminnow (Ptychocheilus Lucius) [Tyus, 1991 ]. This study evaluated the
' geomorphic basis of nursery habitat and year-to-year changes in habitat availability in order to
improve recommendations for flood flows that form and maintain nursery habitat and for low
flows at which these habitats are used.
' Neazly every major river in the western United States is controlled by one or more large
dams. Much research has shown that the river downstream from a dam adjusts physically, and
its waters may change chemically and biologically, after dam completion [e.g., Williams and
Wolman, 1984; Tyus, 1992]. These changes affect the downstream river and its floodplain. The
dams of the Colorado River basin, such as Flaming Gorge Dam on the Green River, Utah, have
greatly altered the river corridor, and these ecosystem changes are believed to be a factor in the
' decline of endangered fish populations to critical levels [Minckley and Deacon, 1991]. One of
the many dam-related factors that may be responsible for the demise of these populations is the
availability of nursery habitat for larval fish [Tyus and Kazp, 1991]. Consequently, species
' recovery, as mandated by the Endangered Species Act (ESA), will in part depend on
enhancement of available nursery habitat.
The purpose of this research was to evaluate the geomorphic basis of nursery habitat, and
to determine if there are annual changes in nursery habitat availability for the endangered
Colorado pikeminnow within the Ouray National Wildlife Refuge (Ouray NWR) neaz Ouray,
Utah (Figure 1). Unlike previous efforts to quantify nursery habitat in the Green River [e.g.,
Pucherelli et al., 1990], I integrated interdisciplinary data from multiple spatial scales collected
during a multiyeaz period. I used these data to address how nursery habitat characteristics and
' availability aze affected by different flow regimes of the Green River. Results from this research
may improve recommendations for releases from Flaming Gorge Dam that form, maintain, and
maximize Colorado pikeminnow nursery habitat. The objectives of this study were to determine
' the bed- and barforms that create nursery habitat, the effect ofhabitat-forming geomorphic
features on the flow field at low flow, the relationship between habitat availability and discharge,
and the yeaz-to-yeaz changes in habitat availability caused by different flood flows and
' subsequent low flows.
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