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

GREEN AND YAMPA RIVER COMPLEX
The Service considers the Yampa and Green Rivers as a system that is essential
to the survival and recovery of the endangered fish, primarily because of
their biologic and hydrologic interrelationshipsR The Green River above its
confluence with the Yampa River has been altered (hydrograph, temperature,
sediment transport, fish habitat, and stream species composition) by
construction and operation of Flaming Gorge Dam. Yampa River flows, however,
remain predominately unregulated and follow a more natural hydrograph.
Relative to the Green River, the Yampa River has higher spring and summer
water temperatures, and its input of sediment promotes the creation and
maintenance of backwater nursery habitats for Colorado squawfish in the-Green
River. Operation of Flaming Gorge Dam has altered the magnitude, duration,
and timing of the spring peak and has increased base flows in the Green River.
This-had negative impacts on the nursery habitat for Colorado squawfish and
razorback sucker.
Sediment and stream channel morphology in the Green River are maintained
somewhat by spring runoff from the Yampa River (Tyus and Karp 1989). Sediment
import into the Green River from the Yampa River contributes to the system's
present sediment quasi-equilibrium (Lyons 1989). This sediment is important
in creating backwaters and other important habitats for endangered fish.
The Green and Yampa Rivers also are interrelated biologically. Colorado
squawfish migrate from the Green River to spawn in the Yampa River; the larvae
are then transported back to Green River nursery habitats. Movement of adult
endangered fish, between the Green and Yampa Rivers, was well documented by
Tyus (1990), Tyus and Haines (1991), and others.
ENDANGERED FISH
The importance of the Green River to rare and endangered fish was established
by the Recovery Program and recognized by many biologists as noted in the
recovery plans for each of the species. The Green River and its tributaries
were 1-fisted as the highest priority for recovery of Colorado squawfish in the
Colorado River Basin in the recently revised Colorado squawfish Recovery Plan
(U.S. Fish and Wildlife Service 1991). The Green River in Desolation and Gray
Canyons and in Dinosaur National Monument (Dinosaur) is considered extremely
important in the recovery of humpback chub in the Humpback Chub Recovery Plan
(U.S. Fish and Wildlife Service 1990a). The Bonytail Chub Recovery Plan
(U.S. Fish and Wildlife Service 1990b) indicates that one of the lest known
riverine concentrations of bonytail chub was in the Green River within
Dinosaur. In addition, the Green River supports the largest known population
of razorback sucker in their natural riverine habitat (Lanigan and Tyus 1989).