8188

• UCREFRP Catalog Number: 8188
• Author: Muth, R. T., et al.
• Title: Flow and Temperature Recommendations for Endangered Fishes in the Green River Downstream of Flaming Forge Dam.
• USFW Year: 2000.
• USFW - Doc Type: \
• Copyright Material: NO

Final Report

September 2000

fish with cues to begin spawning migrations and reproduction. Elevation of reworked in-channel
sediment deposits is set by the magnitude of the spring peak and declining post-peak flows.
During summer and autumn base flows, nursery habitats form in low-velocity areas associated
with sediment deposits. Conditions in the nursery habitats during this period are critical for
growth and survival of age-O Colorado pikeminnow.

The Green River system supports the largest remaining riverine population of razorback
suckers. However, recruitment is insufficient, and their population is declining to precariously
low levels. Lack of recruitment is attributed primarily to low production of larvae and high
mortality of early life stages. Floodplain habitats, which are important for all life stages of the
razorback sucker, are critical for survival of early life stages because they provide warm, food-
rich environments. Restoring access to inundated floodplain habitats appears to be crucial for the
recovery of the razorback sucker. Spring peaks of sufficient frequency, magnitude, and duration
to inundate floodplain habitats are needed to enhance growth and survival of young razorback
suckers.

Reproduction and recruitment of humpback chubs occur in Desolation and Gray
Canyons in Reach 3. A few humpback chubs occur in Whirlpool and Split Mountain Canyons of
upper Reach 2, but the current abundance and life history of chubs in those areas are unknown.
High spring flows prepare spawning habitats and provide the fish with cues for spawning, which
occurs as runoff declines in late spring. Young fish inhabit low-velocity shorelines and backwater
habitats as flow decreases during summer. Older juveniles inhabit deeper offshore eddies, often
in association with boulders or other cover. Large eddies form at high flow and provide habitat in
which humpback chubs spawn and feed on entrained allochthonous materials. Complex shoreline
habitats used by larvae and juveniles are available at relatively low base flows during summer
and autumn.

Information on each endangered fish species was used to develop integrated flow and
temperature recommendations for the Green River downstream of Flaming Gorge Dam. The goal
of the recommendations is to provide the annual and seasonal flow and temperature patterns in
the Green River that would enhance populations of the endangered fishes. Six objectives were
developed to achieve this goal: (1) provide appropriate conditions that allow gonadal maturation
and environmental cues for spawning movements and reproduction; (2) form low-velocity
habitats for pre-spawning staging and post-spawning feeding and resting areas; (3) inundate
floodplains and other off-channel habitats at the appropriate time and for an adequate duration to
provide warm, food-rich environments for fish growth and conditioning and to provide river-
floodplain connections for the restoration of natural ecosystem processes; (4) restore and
maintain the channel complexity and dynamics needed for the formation and maintenance of
high-quality spawning, nursery, and adult habitats; (5) provide base flows that promote favorable
conditions in low-velocity habitats during summer, autumn, and winter; and (6) minimize
differences in water temperature between the Green River and Yampa River in Echo Park to
prevent temperature shock and possible mortality to larval Colorado pikeminnow transported
from the Yampa River and into the Green River during summer.

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