1006

• UCREFRP Catalog Number: 1006
• Author: Resource Consultants, I.
• Title: Biological Assessment Green Mountain Reservoir Water Marketing Program.
• USFW Year: 1985.
• USFW - Doc Type: Denver.
• Copyright Material: NO

I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I

Service (Archer et al 1984) did collect more y-o-y squawfish in the
Colorado River in 1983 than in previous years, and also found more of
them near Grand Junction where they had seldom been collected pre-
viously. They used a more efficient collection method in 1983, which
might explain this difference.
Therefore, available data support the hypothesis that Colorado
squawfish reproductive success may suffer in areas and years of low
flow. Additionally, the Colorado River has been more depleted than the
Green River, and depletions were initiated earlier in this century
(Joseph et al 1977). Reproductive success of squawfish is lower in the
Colorado River than in the Green River under essentially similar habitat
conditions (Holden 1979, Miller et al 1984, Archer et al 1984). This
would further suggest their is a 1 ink between depl etion of flows and
lowered squawfish reproductive success.
Humpback Chub
Distribution, Abundance and Ecology:
The humpback chub is found in several canyon areas of the upper
Colorado Basi n, and in the Grand Canyon in and near the mouth of the
little Colorado River. In the Colorado River between Grand Junction and
Moab it is found in Westwater Canyon and a portion of Ruby Canyon call ed
Bl ack Rocks (Figure 2). These habitats differ from the rest of the
river by having areas up to 60 feet deep, apparently a necessary element
of good adult humpback chub habitat. Present distribution appears to be
similar to past distribution, except the Grand Canyon population is
greatly reduced due to the cold tailwaters of Glen Canyon Dam and a
population in the upper Green River was eliminated by Flaming Gorge Dam.

- 25 -