9678

• UCREFRP Catalog Number: 9678
• Author: Tyus, H. M. and C. A. Karp.
• Title: Habitat Use and Streamflow Needs of Rare and Endangered Fishes
• USFW Year: 1990.
• USFW - Doc Type: Flaming Gorge Studies - Draft Consolidated Report Preliminary.
• Copyright Material: NO

Fluctuating winter flows with icy conditions may cause movement of
overwintering adults, and this presumably causes stress. Stable flows are
recommended.
Recommendations
Flow and Temperature
Decline and endangerment of the Colorado River fishes is due in part, to
human-induced habitat changes. Closure and operation of Flaming Gorge and
Fontenelle dams on the upper Green River eliminated most of the native fishes
in 128 km of river above DNM (Baxter and Simon 1970, Vanicek et al. 1970) and
current operations do not provide desirable flow and temperature conditions
for downstream native fish populations. Standing crops of endangered fishes in
the Green River below its confluence with the Yampa River are presumably being
maintained by the more natural flow and temperature regimens of that system
(Tyus and Karp 1989). Reproduction of Colorado squawfish in the lower Green
River continues because of mitigating affects of tributary flows and increased
distance from Flaming Gorge Dam.
Miller et al. (1982c) provided some flow recommendations for Colorado
squawfish in the Green River which considered survival, rather than
maintenance or recovery, of self-sustaining populations. These investigators
recognized that additional flows were needed to maintain endangered fish
habitat, but could not identify them because of limited information. Operation
of Flaming Gorge Dam can be altered to aid recovery of the endangered
Colorado River fishes. Efforts to coordinate timing of key Green (via
operation of Flaming Gorge Dam) and Yampa river flow events should be
explored for recovery of the rare fishes in the Green River basin.
Acceptable flows and temperatures will require two major changes in
Flaming Gorge operations: higher and warmer spring releases, and lower, more
stable flows during the remainder of the year. Recommended flow regimes, by
season are:
SPring (March 21-June 21)
Flaming Gorge releases should pattern spring flows of the Yampa River,
particularly with respect to timing and duration. Maximum streamflow of 113.2
m /s or more of warmest available water (highest lake levels) should be
provided annually. These releases should be synchronized with Yampa River
spring runoff, and occur for a period o~ about three to six weeks, resulting
in an average flow in excess of 367.9 m /s at Ouray, ~tah (sum of average peak
flow at mouth of Yampa River, 254.7 m3/s, and 113.2 m /s released fr~m Flaming
Gorge Dam). This flow should be followed by flows of at least 56.6 m /s for an
additional week. Bottomlands in the Jensen and Ouray areas would thereby be
flooded but fish access may need improvement. Water temperatures during
Colorado squawfish migrations should range from 14°C or more on May 23 to
about 22°C on July 27. Water temperature should reach 20°C by June 1.
Summer (June 22-September 22)
Green River flows should decrease gradually in concert with the emergence
of larval Colorado squawfish on spawning grounds in Yampa and Desolation-Gray
canyons. The flow regimen of the Green River should resemble (in timing,
duration) the hydrologic conditions of the Yampa River with respect to low,
moderate, and high water flows. Gradual decreases in spring flows sho~ld be
initiated with larval drift, attaining a target flow of about 50.94 m /s at
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