9305

• UCREFRP Catalog Number: 9305
• Author: U.S. Fish and Wildlife Service.
• Title: Final Biological Opinion for the Operation of Flaming Gorge Dam.
• USFW Year: 1992.
• USFW - Doc Type: Denver, CO.
• Copyright Material: NO

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staging fish. High spring flows mobilize and deliver-nutrients and sediments
downstream and aid in the formation of nursery areas. Additional studies are
required to refine this relationship.
Humpback Chub
r+
Humpback chub predominantly use high-gradient, rocky, canyon habitats, and
availability of such habitat may be adversely affected b,~ the present
alteration of spring runoff in the Green River. Spawning of humpback chub
occurs shortly after highest spring discharge at river temperatures of about
20 °C in the Yampa River, and presumably in the Green River as well. Reduced
spring runoff promotes growth of the introduced salt cedar, Tamarix spp.
resulting in bank stabilization and increased availability of spawning habitat
for introduced fish. Relationships between magnitude and duration of spring
runoff should be further evaluated with a consideration of availability of
shoreline eddy habitat,. bank stabilization due to exotic vegetation,
overgrowth, and abundance of nonnative and other potential competitor and
predator fish.
Razor ack Sucker
Spawning of razorback suckers occurs with increasing flows associated with
highest spring runoff. Curtailment of spring runoff in the mainstream Green
River may be associated with loss of recruitment to the juvenile stage.
Overbank flooding during spring runoff is considered beneficial to adults and
may be important for dispersal and rearing of young. Flaming Gorge releases
should promote spring flooding of historic flooded lowlands. Influence of
spring flows on razorback sucker spawn in the Green River should be more fully
evaluated.
Bonvtail Chub
Because so few bonytail chub were collected in the wild, their spring behavior
and requirements are unknown. It is hypothesized that if the habitat and life
history requirements of squawfish, humpback chub, and razorback suckers are
met, tfien the remaining bonytail chub will benefit.
Su_
Colorado Soua fish
Gradually decreasing flows and sediment transport regimens and warming river
temperatures in early and midsummer are necessary for successful spawning,
hatching, and downstream transport of drifting larvae. The gradual decline of
summer flows following spring scouring maintains natural sediment transport
equilibria, prevents siltation of spawning substrate, aids downstream drift of
larvae, and creates productive nursery areas.
Humpback Chub
Rapidly declining summer flows adversely affects spawning and nursery habitats
by concentrating fish in suboptimal habitats and increasing the potential for