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

4-5

September 2000

Table 4.1.-Continued.

a Abundant = occurring in large numbers and consistently collected in a designated area; common = occurring in
moderate numbers and frequently collected in a designated area; rare = occurring in low numbers, either in a restricted
area or having a sporadic distribution over a larger area; incidental = occurring in very low numbers and known from
only a few collections. Endangered species are defined in text box on page 1-1.

b The Kendall Warm Springs dace (Rhinichthys osculus thermalis) is a federally listed endangered subspecies restricted
to Kendall Warm Springs in the upper Green River drainage, Wyoming.

C Includes native Colorado River cutthroat trout (Oncorhynchus clarki pleuriticus) and nonnative Snake River
Yellowstone cutthroat trout (Oncorhynchus clarki bouvieri) and Bear Lake Bonneville cutthroat trout (Oncorhynchus
clarki utah).

Sources: Behnke et al. (1982), Tyus et al. (1982a), Miller and Hubert (1990), Maddux et al. (1993), Muth and Nesler
(1993), McAda et al. (1994a, 1994b, 1995, 1996, 1997), Hlohowskyj and Hayse (1995). Information also came from
personal communications with T. E. Chart and K. D. Christopherson of the Utah Division of Wildlife Resources and
T. Modde of the U.S. Fish and Wildlife Service.

Before construction of Flaming Gorge Dam, the Green Ri ver exhibited seasonal fluctuations
in flow, and water temperatures ranged from near freezing to greater than 200C (Vanicek et al. 1970).
Warm-water reaches of the Green River in and downstream of Flaming Gorge Canyon supported
native fishes (including humpback chub, bonytail, Colorado pikeminnow, and razorback sucker) and
some nonnative fishes; most of these species were successfully reproducing in the river upstream of
its confluence with the Yampa River (Vanicek et al. 1970; Holden and Stalnaker 1975a;
Holden 1979, 1991). Trout were absent from this portion of the river (Holden and Crist 1981).

After closure of the dam, hypolimnetic releases of cold, clear water allowed for the
establishment of a tailwater trout fishery and reduced or eliminated populations of warm-
water-adapted fishes downstream to the Yampa River confluence (Holden and Crist 1981). An
additional perturbation occurred in 1962, when 700-800 km of the Green River and its tributaries
were treated with the fish toxicant rotenone. The goal of this controversial project was to remove
unwanted "coarse" fishes and allow Flaming Gorge Reservoir and its inflowing streams to realize
their full potential as trout fisheries (Miller 1963; Dexter 1965; Pearson et al. 1968). Downstream
detoxification failed, and rare endemic fishes were killed in Dinosaur National Monument (Holden
1991). The present tailwater fish community consists of native Colorado River cutthroat trout and
several subspecies (Table 4.1) or species (Section 4.1.2) of nonnative trout, which largely are
maintained by stocking; nonnative brown trout reproduce throughout most of Reach 1.

Penstocks at Flaming Gorge Dam were modified in 1978 to permit withdrawal of warmer
water from selected reservoir depths (Section 3.2), thereby increasing temperatures in the tai1waters
and downstream to levels better suited for trout production and growth (Holden and Crist 1981;
Modde et al. 1991). As a result, the growth rates of trout improved, and the fishery is now
well-recognized for abundant, large fish. However, it is interesting to note that the temperature of