9417

• UCREFRP Catalog Number: 9417
• Author: U.S. Department of the Interior.
• Title: Final Environmental Assessment
• USFW Year: 1998.
• USFW - Doc Type: Acquisition and Enhancement of Floodplain Habitats along the Upper Colorado, Green, and Gunnison Rivers as part of the Recovery Program for Endangered Colorado River Fishes.
• Copyright Material: NO

survive to adulthood (Tyus and Karp 1990;
Minckley et al. 1991; Modde et al. 1996),

After they hatch, young larval fish need an
immediate food source to survive. They must
initiate feeding during the "critical period" after
swim-up or they will die from starvation (Miller et
al. 1988). The "critical period for larval razorbacks
lasts from about 7 to 21 days after hatching
(Minckley et al. 1991). The larvae and juveniles of
all endangered Colorado River fishes feed on
zooplankton (Miller et al. 1982), When compared
to other riverine habitats, inundated floodplains
have proven to produce the highest densities of
zooplankton (Welcomme 1989).

These off-channel habitats not only produce food
of the proper quantity and size, they produce this
food at the time it is needed by the larval fish
(Modde 1997). Finding ways to increase
zooplankton production in off-channel habitats is
expected to increase the survival of young fish.

H. Distribution of Floodplain Habitat

Bottomland habitats in the upper Colorado River
basin were inventoried during 1993 by Irving and
Burdick (1995). Along the Green River, the
highest concentration of floodplain habitats is
located between Pariette Draw and Dinosaur
National Monument (Figure 1-5). Along the
Colorado and Gunnison rivers, the highest
concentrations of habitats are located within three
general areas (Figure 1-3):

(1) the Colorado River between Rifle and
DeBeque, Colorado;

(2) the Grand Valley reach of the Colorado
River between Fruita (Lorna) and Palisade,
Colorado; and

(3) the Gunnison River near Delta,
Colorado.

Criteria used to identify parcels of land suitable for

Colorado River System

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Figure \.3, General location map for the project a1D;g the Colorado anl
Gunnison Riveu. Major floodplains are shown by the shaded areas.

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acquisition and restoration as floodplain habitat are:

(1) Biological Importance - areas where
razorback suckers currently reside and/or they were
historically common to abundant;

(2) "Floodability" - areas that currently
flood or can be made to flood at lower flows;

(3) Contaminants - sites which are not
contaminated; and

(4) Size - parcel's surface area.

An estimated 3,588 acres of bottomland along the
Upper Colorado River meet these criteria. These
lands are adjacent to 113 miles of river between
Westwater Canyon (Lorna) at the Colorado-Utah
State Line and Rifle, Colorado. Razorback suckers
are believed to have been historically abundant in
this area (Quartarone 1993). Below Palisade, this
reach is also a high concentration area for adult
Colorado squawfish, and includes larval nursery
areas and historical spawning sites.

Floodplain habitats that meet the above criteria

1-4