WSP07668

• File Number: 8240.200.10.C.5
• Description: UCRBRIP
• Basin: Colorado Mainstem
• Date: 3/21/1994
• Author: USFWS
• Title: Federal Register - Determination of Critical Habitat for Four Colorado River Endangered Fishes - Final Rule
• Water Supply Pro - Doc Type: Publication

11374

Federal Register / Vol. 59, No, 54 / Monday, March 21, 1994 / Rules and Regulations
d .

DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

RIN 1018-AB91

Endangered and Threatened Wildlife
and Plants; Determination of Critical
Habitat for the Colorado River
Endangered Fishes: Razorback
Sucker, Colorado Squawflsh,
Humpback Chub, and Bonytall Chub

AGENCY: Fish and Wildlife Service,
Interior.
Acr'ON: Final rule.

SUMMARY: The Fish and Wildlife Service
designates critical habitat for four
species of endemic Colorado River
Basin fishes: Razorback sucker
(Xyrauchen texanus), Colorado
squawfish (Ptyr:hacheilus lucius),
humpback chub [Gila cypha), and
bonytail chub (Gila elegans). These
species are listed as endangered under
the Endangered Species Act of 1973, as
amended. The critical habitat
designated is located primarily on
Federal land and, to a lesser extent, on
tribal, State, and private lands. The
designation provides additional
protection required under section 7 of
the Act with regard 10 activities that
.require Federal agency action. The
Service designates 3,168 Jan (1,980 mil
of critical hahitat for the four Colorado
River endangered fishes in portions of
Colorado. Utah..New Mexico, Arizona,
Nevada, and California. The areas
designated for each species also overlap
some areas designated for the other
species.
EFFECTIVE DATE: April 20, 1994.
ADDRESSES: The complete file for this
rule is available for public inspection,
by appointment; during nonnal business
hours et the office of the Field
Supervisor, Ecological Services, U.S.
Fish and Wildlife Service, 2060
Administration Building, 1745 West
1700 South, Salt Lake City. Utah 84104.
FOR FURTHER INFORMATION CONTACT:
Reed E. Harris. Field Supervisor, at the
above address, telephone [phone].

SUPPLEMENTARY'INFORMA nON:

Background

The four endangered fishes are
endemic to the Colorado River Basin
(Basin), which consists of portions of
seven Western States. The Basin drains
approximately 627,000 Jan. (242.000
rni2) within the United States and has
been politically divided into an Upper
and Lower Basin. The Upper Basin
consists of portions of the States of

Colorado, New Mexico, Utah, and
Wyoming. The Lower Basin consists of
portions of the States of Arizona," .
California, and Nevada. An additional
5,000 Jan' (2,000 mi') of the Basin lies
within Mexico,
Historically. the native fish fauna of
the Basin was dominated by the
minnow'(cyprinids) and sucker
(catostomids) families (Minckley et al.
1986). The four species of concern. the
razorback sucker (Xyrauchen texonus),
Colorado squawfish (Ptychocheilus
lucius). humpback chub (Gila cypha),
and bonytail chub (Gila elegans) are
listed as endangered under the
Endangered Species Act (Act) of 1973.
as amended (16 U.S.C. 1531 et seq.).
These fishes are threatened .with
extinction due to the cumulative effects
of environmental impacts that have
resulted in habitat loss (including
alterations to natural flows and changes
to temperature and sediment regimes),
proliferation of nonnative introduced
fish. and other man.induced
disturbances (Miller 1961; Minckley
1973; U.S, Fish and Wildlife Service
[USFWSJ 1987; Carlson and Muth
1989).
Natural Colorado squaw!ish
papulations survive only in the Upper
Basin, where their numbers are
relatively high only in the Green River
Basin of Utah and Colorado (compared
with other rivers in the Upper Basin)
(Tyus 1991). Razorback sucker and
bonytail chub populations throughout
. the Basin consist predominately of old
adult !ish, Populations persist primarily
because of the longevity of these species
(USFWS 1990a; Minckley et a!. 1991).
although some experimental and
augmentation programs have stocked
fish in the Basin. Humpback chub
populations in the Little Colorado River,
Black Rocks, and Westwater Canyon in
the Colorado River appear relatively
stable in number of fish, but declines
have occurred in other locations
(USFWS 1990b).
The historical ranges of the four
endangered fishes have been fragmented
by construction of dams and water
diversions throughout the Basin
(Carlson and Muth 1989), The Fish and
Wildlife Service (Service) believes that
it is important to the survival and
recovery of these species to maintain
and reestablish populations in
geographically distinct areas within
their .historic range that provida varying
thennal, chemical, geological, and
physical parameters required for .
maintenance of genomes.
Conservation of these four species
will require the identification arid
management of water resources and
habitat components that are considered

important to any fish species, such as
spawning areas, nursery grounds. and
interactions with predators and
competitors. However, because the four
endangered !ishesara present in such
low numbers, basic life history and
habitat use information has been
difficult to obtain. Changes to the
historical Colorado River Basin
ecosystem that have resulted in a lack
. of reproduction and/or recruitment have
been hypothesized as factors in their
.endangerment (USFWS 1990a. 1990b,
1991: Minckley et al. 1991). In this case,
not only would a lack of successful
recruitment lead to small numbers of
fish. but over time, remnant stocks may
lose genetic diversity. Ultimately,
extinction could result because the loss
of genetic diversity may make
populations less able to adjust to
enviromnental change,

Habitats and Status of Endangered Fish

Affected Environment

The four Colorado River endangered
fishes evolved in the Colorado River
Basin (Basin) and were adapted to the
natural environment that existed prior
to the beginning of lllIge.scale water
development and introduction of
nonnative species. This natural
environment was characterized by
highly fluctuating seasonal. and annual
flows, distinctly different habitat types
(i.e" whitewater, lower gradient and
meandering main channels, off.channel
backwaters, and others) and varying
water quality (i.e., sediment load,
temperature. salinity, etc.). Recent
population declines and disappearances
of endemic Basin fish species from
much of their former range have been
associated with the onset of rapid and
widespread anthropogenic changes to
the natural environment, The
cumulative environmental impact of
these changes has resulted in alteration
of the physical and biological
characteristics of many rivers in the
Basin. These impacts presumably
occurred so rapidiy that the fish could
not adapt to them (Carlson and Muth
1989). Dams and diversions have
fragmented fonner fish habitat and
restricted fish movement. As a result.
genetic interchange (emigration and
immigration of individuals) between
some fish populations is no longer
possible. High flood flows were once
nonnal in the Basin and provided food
and nutrient exchange between river
channels and shallow-water flood plain
hahitats. These high flows are now
controlled by numerous dams. As a
. result of these dams, major changes also
have occurred in .water quality,
quantity. lemperature, sediment load