7152

• UCREFRP Catalog Number: 7152
• Author: Holden, P. B.
• Title: Relationship between Flows in the Yampa River and Success of Rare Fish Populations in the Green River System.
• USFW Year: 1980.
• USFW - Doc Type: Logan, Utah.
• Copyright Material: NO

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Monument in 1974-1976, but failed to find any young squawfish. Holden
and Crist (1978) found three yearling squawfish in Island Park in 1978
and one yearling there in 1979 (Holden and Crist 1980). The seining

effort expended by these researchers from 1967-1979 was considerably
lower on a yearly basis than Vanicek's (1967) effort. Sampling varied

from year to year, but sufficient effort was expended that young squaw-
fish, at least a few, would have been found if they were present. The
most intensive effort during these years was that of Holden and Crist
(1979 and 1980). The low numbers of fish they foun~, and the failure

to see any suggestion of good reproductive success, is similar to the

conditions found by the other investigators from 1967-1977. These data

show that reproductive success of Colorado squawfish essentially col-
lapsed in about 1967-1968, changing from a strong reproductive position
to one of essentially no reproductive success.

A similar collapse of the trophy trout fishery immediately below
Flaming Gorge Dam also occurred in about 1967 or 1968. Holden and
Crist (1978) showed that these simultaneous declines in the squawfish

and trout populations were correlated with an increase in the flow re-

leased from Flaming Gorge since 1967, compared to the 1963-1966 period.
Table 4 is a listing of mean monthly flows and temperatures at the
Greendale USGS gauge for the periods 1951-1962 (pre-Flaming Gorge Dam),
1963-1966 (immediately after closure of Flaming Gorge), and 1967-1977
(normal operational mode for the dam). These data show that Flaming
Gorge Dam had a tremendous impact on the natural flows and temperatures
of the Green River, and that releases from 1963-1966 were fairly low.

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