9434

• UCREFRP Catalog Number: 9434
• Author: Chart, T. E., K. L. Orchard, J. C. Schmidt, K. S. Day, K. D. Christopherson, C. Crosby and L. Lynch.
• Title: Flaming Gorge Studies
• USFW Year: 2000.
• USFW - Doc Type: Reproduction and Recruitment of Gila Spp. and Colorado Pikeminnow in the Middle Green River.
• Copyright Material: NO

hydrograph when water temperatures near 20°C. Larvae drift great distances from the hatching
site before occupying backwater habitats in nursery areas. The use of backwaters by young
pikeminnow has been reported by several authors. Haines and Tyus (1990) stated that Colorado
pikeminnow used backwaters greater than 0.15 m deep and were found more frequently in
backwater with surface area greater than 750 mZ. Tyus and Haines (1991} also reported
pikeminnow used backwater that were deeper, warmer (mean 2°C) and more turbid than those
not used. Concurrent investigations of pikeminnow nursery habitat use in the low gradient
stretches of the Green River above and below Deso/Gray report similar findings (Trammell and
Chart 1999; Day et a1.1999b). However neither of these researchers found a direct correlation
with catch rate of YOY pikeminnow and habitat availability. Habitat availability was negatively
correlated with the spring peak in both areas. Previous descriptions of YOY pikeminnow habitat
use in canyon bound stretches of the Green River are lacking.
The goal of this project (Flaming Gorge Project No. 39) was to determine if test flows
from Flaming Gorge Dam optimize habitats needed for adequate reproduction and recruitment of
Gila spp. and. Colorado pikeminnow in this portion of the Middle Green River or to propose
modifications to existing recommendations as needed. To address this goal, three related studies
were conducted. The first study (Report A: Orchard and Schmidt 1998) dealt with the effect of
varying flow levels on the availability of low velocity eddies, a habitat preferred by the juvenile
and adult life stages of endangered humpback chub. Extent anal distribution of eddies were
mapped at flows ranging between 2,100 and 27;000 cubic feet per second (cfs). In addition,
changes in the channel geometry since the 1920's were determined through examination of
historical photographs. From that analysis, presumed long term changes in the availability of
eddy habitat was modeled.
The second study (Report B: Day et al. 1999) was designed to determine reproductive
success of Gila spp. and Colorado pikeminnow and establish a link between the fgrmation and
maintenance of preferred nursery habitat and Green River flow. Sampling trips occurred
throughout the summer, fall and spring to track the relative abundance of these species and
characterize their habitat use.
The third study (Report C: Chart and Lentsch 1998) focused on monitoring the entire fish
community which provided a measure of Gila spp. and. Colorado pikeminnow recruitment to
Age l+ and later life stages. Monitoring consisted of one mid-summer sampling trip each year
of the study, which. incorporated a variety of sampling techniques. A corollary to the monitoring
efforts was investigations into suspected Colorado pikeminnow spawning at locations other than
the documented site at Three Fords rapid (RK 250). Although this study was not initiated as part
of the Flaming Gorge studies until 1994, i.e., a three year study, pre-project data were
incorporated whenever possible.
STUDY OBJECTIVES
The goal of these studies was to determine if test flows from Flaming Gorge Dam
optimize habitats needed for adequate reproduction and recruitment of Gila spp and Colorado
pikeminnow in the Middle Green River or to propose modifications to existing
recommendations. There were a total often project objectives as identified in the original scope
of work: six dealt with the biological component; four addressed the geomorphic component.
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