8253

• UCREFRP Catalog Number: 8253
• Author: Schmidt, J. C.
• Title: Geomorphic Control of the Distribution of Age-0 Colorado Squawfish in the Green River in Colorado and Utah.
• USFW Year: 1996.
• USFW - Doc Type: Logan, Utah.
• Copyright Material: NO

2
Abstract. Regional geology controls the geomorphic organization of the Green River
in Colorado and Utah and produces a series of river segments that are either restricted
meanders, fixed meanders, or canyons with abundant debris fans. The distribution of
channel planform controls the distribution of shoreline complexity, and there is no
systematic downstream change in channel planform or in shoreline complexity.
Backwater habitats, which typically are abundant where complexity is high, are used as
nursery areas by age-0 Colorado squawfish Ptychocheilus lucius. Field measurements
of channel and bar topography, air photo and geographic information system analysis,
and simulation modeling show that the location of critical nursery habitat segments of
the river is ultimately determined by channel geomorphology. Longitudinal dispersion
establishes a system-wide pattern wherein downstream segments have higher age-0
populations, but restricted meandering reaches have proportionally higher populations
than predicted soley by longitudinal dispersion. Streamflow at the time of larval drift
also affects population and distribution. The interaction of hydrology, geomorphology,
and the characteristics of spawning and larval drift must be understood collectively if
operations of Flaming Gorge Dam are to be adjusted to maintain the present distribution
of river segments critical as nursery habitats in the Green River.
Keywords. fluvial geomorphology, endangered fish, Green River