9568

• UCREFRP Catalog Number: 9568
• Author: Resource Consultants Inc.
• Title: Sediment Transport Studies of the Little Snake, Yampa, and Green River Systems.
• USFW Year: 1991.
• USFW - Doc Type: Fort Collins, CO.
• Copyright Material: NO

I
I

Previously, the Yampa Canyon was considered a unique environment in that their were no major
dams upstream and only modest water consumption (about 10 percent of annual streamflow, Steele and
others, 1979). Consequently, the river in the lower reaches was considered relatively pristine and
undisturbed by man. With the recent completion of Stagecoach Reservoir on the upper Yampa River
above Steamboat it can no longer be said that there are no major dams upstream; however, due to a large
intervening drainage area the lower reaches are still considered relatively free flowing and pristine. The
Sandstone Reservoir project, proposed for the upper Little Snake drainage, could further modify the Yampa
Canyon hydrology.

I

I
I

1.3 Critical Habitat Reaches (after Tws and ~. 1988)

I
I
I
I

The Colorado squawfish, humpback chub, bonytail chub, and razorback sucker are four endemic
fishes that were historically common-to-abundant in the Colorado River basin, including the lower Yampa
River. However, these fishes are threatened with extinction throughout the basin due to the combined
effects of habitat loss and alteration, introduction of non-native competitors and predators, and other man-
induced impacts. The Colorado squawfish, humpback chub and bonytail chub are federally listed as
endangered species, while the razorback sucker is protected in the states of Arizona, California, Nevada,
Colorado, and Utah and is a candidate species for federal endangered listing.

Colorado Sauawfish

I
I
I
I
I
I
I
I
I
I

Adult Colorado squawfish are distributed throughout the mainstem Yampa River from its mouth
to Craig, Colorado; however, spawning occurs primarily in the lower 32 miles of the Yampa Canyon,
particularly in the reach from Warm Springs rapid (river mile (rm) 4.1) to Harding Hole (rm 20).
Numerous captures of ripe fish in a 4 mile reach near Mathers Hole (rm 17.7) suggested that egg
deposition and fertilization may be concentrated in this area where large, deep pools and eddies are
intermingled with runs and cobble bars of gravel, cobble, and boulder substrate. Spawning behavior is
divided into two phases: resting-staging phase in pools or large shoreline eddies, and deposition-
fertilization phase on cobble bars. A clean cobble substrate is considered necessary for spawning. After
spring runoff larval squawflSh emerge as sadry from cobble bars in the canyon reach and drift downstream
to concentrate in shallow backwater areas on the Green River.

Humpback Chub

Adult humpback chub have been captured in canyon-bound habitat in the lower 56 miles of the
Yampa River and the lower 10 miles of the Little Snake. In the canyon, the fish were most often collected
in eddy habitat areas (average depth 5 feet), particularly shoreline eddies created by boulders. Spawning
occurs shortly after peak spring flows. Young humpback chubs have been caught between no 0.1 and 40 of
the Yampa River, again in shoreline eddies and runs.

Bonytail Chub

Habitat requirements of the bony tail chub in the Green River basin are largely unknown.
Captures have occurred primarily in the lower Yampa and upper Green Rivers.

Razorback Sucker

Adult razorback suckers have been captured in flat-water sections of the upper Green River and in
the lower Yampa River. During the nonbreeding season the most common habitat was shoreline runs and
mid-channel sand bars in the Green River. Spawning activity has been documented in the lower Yampa
River (near the Green River confluence) and in the upper Green River.

1-3