7981

• UCREFRP Catalog Number: 7981
• Author: Tyus, H. M.
• Title: Management of Native Warmwater Fishes of the Upper Colorado River. pages 175-182, in Warmwater Fishes Symposium I. Technical Report RM-207.
• USFW Year: 1991.
• USFW - Doc Type: \
• Copyright Material: YES

also become endangered or extinct in the near
future. As each species disappears, it is _,
anticipated that recovery of the remaining forms
will become increasingly more difficult as
perturbations in the native ecosystem increase.
An example is the f1anne1mouth sucker, although
previously reported from a variety of locations
in the lower basin, the fish has now been
extirpated south of Lake Mead (W.L. Minck1ey,
personal communication). Other fishes, including
the roundtail chub G. robustar are uncommon-to-
rare in many_~~in~tream habitats in the upper
Colorado River basin (Tyus et al. 1982). Study
of non-endangered fishes has been primarily
incidental to those done for the listed fishes;
to date, study of the former has been
constrained by an unavailability of funds and
lack of interest.

The Green River System

The Green River system in the upper basin
has long been identified as perhaps the most
acceptable location to determine management
measures necessary for recovery of the
endangered fishes. Reasons for this are include
the premise that life histories and habitat
needs of fishes are best evaluated in systems
that are least altered and the fish most
abundant. It is also assumed that conditions in
which species evolve are also those in which it
is most likely to maintain an adaptive advantage
over other forms. The mainstream Green River and
its major tributary the Yampa River, support the
largest remaining riverine populations of
Colorado squawfish (Holden and Wick 1982; Tyus
1991) and razorback sucker (Lanigan and Tyus
1989). Humpback chub persists in Desolation and
Gray canyons of the Green River (Valdez and
Clemmer 1982; Rosenfeld and Wilkinson 1989) and
in the lower Yampa River (Karp and Tyus 1990).
Bony tail persists only as an incidental species
(Kaeding et a1. 1986), but was formerly common
in the Green River (Vanicek 1967).

However, habitats used by endangered
fishes in the Green River system continue to
change, and an evaluation of optimum habitat
requirements are problematic. Closure and
operation of Flaming Gorge and Fontenelle dams
on the upper Green River in the 1960s eliminated
most of the native fishes in 128 km of river
above Dinosaur National Monument (Baxter and
Simon 1970, Vanicek et a1. 1970) and current
operations do not provide acceptable flow and
temperature conditions for native fish
populations for many miles downstream (Vanicek
et al. 1970). Standing crops of endangered
fishes in the Green River below its confluence
with the Yampa River are presumably being
maintained by the more natural flow and
temperature regimens of the latter system (Tyus
and Karp 1989). Recruitment of Colorado
squawfish in the lower Green River continues,
pr~sumably because of mitigating effects of
trlbutary flows and ambient warming of the river
with increased distance from Flaming Gorge Dam.

--

Lack of recruitment in razorback sucker there,
however, may be associated with loss of habitat
and flow regulation (Tyus and Karp 1991).

MANAGEMENT

Management activities for maintaining,
establishing or restoring native warmwater
Colorado River fishes are virtually unknown. On
the contrary, most of the fisheries management
activities to date have been concerned with
introductions of more familiar, non-native
fishes. More recently, however, endangered
fishes has been a prime concern of various
agencies, and several management options have
been explored in the Green River system to date.
Five, rather inclusive management elements have
been developed by the Upper Colorado River Basin
Recovery Program: Provision of Instream Flows,
Habitat Development and Maintenance, Stocking of
Native Fish Species, Nonnative Species and
Sportfishing Management, and Research,
Monitori ng, and Data Management (Rose and Hami 11
1988}. Each of these elements are presented and
briefly discussed below:

Provision of Instream Flows

Viable populations of Colorado River
fishes must be maintained to allow testing of
various management scenarios. This can only be
accomplished by providing suitable habitat. Of
first consideration is provision and maintenance
of instream flows of the proper quality, timing,
duration, and magnitude. These flows must be
delivered to the proper locations to satisfy the
life history requirements of the various fishes.
The attainment of sufficient quantities of water
requires determination of instream flow needs so
that water can be provided, acquired, or
appropriated. However, flows needed for the
fishes may potentially affect water resources
allocations among and between, the United
States, Mexico, and the states of Arizona,
California, Colorado, Nevada, New Mexico, Utah,
and Wyoming. Because of this, flow
recommendations must be scientifically
defensible if they are to be accepted by various
agencies.

In the Green River, the operation of large
reservoirs upstream of endangered fish habitat
can aid in providing needed instream flows. The
Bureau of Reclamation and the Fish and Wildlife
Service have been cooperating in studies
designed to evaluate the impacts upon the
endangered fishes associated with operation of
Flaming Gorge Dam. These studies, performed
under interagency agreements pursuant to Section
7 of the ESA, have resulted in recommendations
for the operation of the dam to offset impacts
on the fishes.
These include seasonal flow and non-flow related
recommendations that have been developed from
analysis and interpretation of about 10 years of
empirical data (Tyus and Karp 1991). It is not
known if these recommendations will be

ill
if :;
-\,1',
d ,
I "' ~
,i 1; ~ii
l'Ii)'1
ill.

177

II