9388

• UCREFRP Catalog Number: 9388
• Author: Maddux, H. R., W. R. Noonan and L. A. Fitzpatrick.
• Title: Overview of the Proposed Critical Habitat Designation for the Four Colorado River Endangered Fishes.
• USFW Year: 1993.
• USFW - Doc Type: Salt Lake City.
• Copyright Material: NO

element. Food supply is a function of nutrient supply, productivity, and availability to
each life stage of the species. Predation, although considered a normal component of
this environment, may be out of balance due to introduced fish species in some areas.
This may also be true of competition, particularly from nonnative fish species.

These primary constituent elements interact to provide the conditions needed to meet the life
history requirements of these four endangered fishes. The presence of or potential for
suitable conditions resulting from the interaction of the constituent elements was a prime
consideration in selection of proposed critical habitat for the fishes.

Only those areas in the lOO-year floodplain that contain the constituent elements are
considered part of critical habitat. Although critical hapitat may only be seasonally occupied
by the fish, such habitat remains important for their conservation.

The biologically based determination of proposed critical habitat areas consisted of an
inventory and evaluation of areas needed for the survival and recovery of the four species.
The constituent elements and selection criteria were then applied throughout the historical
range of the razorback sucker. For the Colorado squawfish, humpback chub and bony tail, the
biological determination was based on the primary constituent elements, recovery plans for
these species, past Service findings, and other published and non-published sources.
For the razorback sucker, the biological determination was based on the primary constituent
elements, five additional selection criteria determined by the Service, past Service findings,
and other published and non-published sources. A recovery plan for the razorback sucker is
in preparation, but it has not been finalized. The additional selection criteria used included:
1) Areas with known or suspected wild spawning populations although recruitment may be
limiting or nonexistent; 2) Areas where juvenile razorback suckers have been collected or
which seem to provide suitable nursery habitat (backwaters, flooded bottomlands, or coves);
3) Areas currently occupied or that were historically occupied that are considered necessary
for recovery and that have the potential for establishment of razorback sucker; 4) Areas and
water required to maintain rangewide fish distribution, and diversity under a variety of
physical, chemical, and biological conditions; 5) Areas that need special management or
protection to insure razorback sucker survival and recovery.

References Cited

A complete list of all references cited herein is available upon request from the U.S. Fish and
Wildlife Service, Salt Lake City, Utah (address located at beginning of document).

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