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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when young-of-the-year squawfish are generally first found (Vanicek .
and Kramer 1969, Holden and Selby 1979), but none were found. Sampling
effort in 1978 was low but still produced six 1976 year class fish,
17 young-of-the-year, but no yearlings, the 1977 year class. There
is little doubt that 1977 was in fact a very poor year for Colorado

squawfish reproductive success in the area between Jensen and Ouray.
Therefore the data in Table 1 accurately portrays reproductive status
of Colorado squawfish for the period 1975-1979, and all years, except
1977, were reproductively successful for the squawfish.
Comparing this data with flows in 1975-1979 (Figures 3-7) shows
that all years exhibited rather natural flows, except 1977 (Figure 5).
The loss of a high spring flow, attributable to very little runoff
from the Yampa River, appears to be the major factor that is different

in the hydrograph for 1977 (Figure 5). During most years, a high

spring peak occurs in either Mayor June, then recedes in late June and

July. Also in all normal years (1975, 1976, 1978, and 1979), the major

portion of the spring flow is Yampa River water because releases from
Flaming Gorge Dam are regulated and do not exceed 4400 cfs. In 1977,
the Green River provided most of the flow at the Jensen USGS gauge
except during May and June when about one-half of the Jensen flow was
due to the Yampa inflow. These data show that the Yampa River is very
important to the success of Colorado squawfish in the upper Green River
and that major reductions in its spring flow would be very detrimental to
Colorado squawfish.

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