7428

• UCREFRP Catalog Number: 7428
• Author: Tyus, H. M.
• Title: Management of Native Warmwater Fishes of the Upper Colorado River.
• USFW Year: 1990.
• USFW - Doc Type: \
• Copyright Material: NO

extinct in the near future. As each species disappears; it is anticipated that
r_ecov~y Qf_-the-remaining forms will become increasingly more difficult.
~~~~o, perturbations in the native ecosyste~i-nom-ate-. An example is the flannelmouth
=" 'sucker, a oug~reviousiy reported from a variety of locations in the lower ABC. '''
~`"~~~t~~basi n, the fish has now been extirpated south of Lake Mead (W. L. Mi nckl ey, ~,,.,;,~
~I2cov~
personal communication). Other fishes, including the roundtail chub G. ~~~~~~ ~
robusta) are uncommon-to-rare in many mainstream habitats in the upper ~V~ky~~~
Colorado River basin (Tyus et al. I98Z). 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 ~Z'"""'\
interest. Maw 5 ~~
~, The Green River System
~•~ ,~~ The Green River system in the upper basin has long been identified as
~~n'' ~ perhaps the most acceptable location to determine management measures
'~~ ~o- 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 ,r
~,~ '` assumed that conditions in which species evolve are also those in which it is~Q,r6,~`a
~ most likely to maintain an adaptive advantage over other forms. The Green
River supports the largest remainin riverine populations of Colorado
squawfish (Holden and Wick 1982; Tyus .f~~ 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}. Bonytail persists only as an
incidental species (Kaeding et al. 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
al. 1910) 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, presumably because of mitigating effects of tributary f]ows 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 (T us and Karp 1991).
MANAGEMENT
Management activities for endangered fishes has been a prime concern of
various agencies, and several have been explored in the Green River system to
date. Five management elements were 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
4