9678

• UCREFRP Catalog Number: 9678
• Author: Tyus, H. M. and C. A. Karp.
• Title: Habitat Use and Streamflow Needs of Rare and Endangered Fishes
• USFW Year: 1990.
• USFW - Doc Type: Flaming Gorge Studies - Draft Consolidated Report Preliminary.
• Copyright Material: NO

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protected as endangered species under provisions of the Endangered Species Act
of 1973 (U. S. Fish and Wildlife Service 1986). The razorback sucker, a
candidate species for federal listing, is protected by state statutes in
Arizona, California, Colorado, Nevada, and Utah (U.S. Fish and Wildlife
Service 1985, 1987a).
In the lower Colorado River basin (below Lee Ferry, AZ), the Colorado
squawfish has been extirpated, relict populations of bonytail chub and
razorback sucker remain in some impoundments but neither species are presumed
self-sustaining, and humpback chub reproduce only in the Little Colorado River
(Hinckley 1973, 1983; Kaeding and Zimmerman 1983; C.O. Hinckley, pers.
comm.). In the upper Colorado River basin, Colorado squawfish persists in the
Yampa and lower Green (below the confluence of the Yampa River) rivers, the
upper Colorado River mainstream, and the lower San Juan River (Archer et al.
1985; Meyer and Moretti 1988; Tyus 1990). The humpback chub is reproducing
successfully in the Yampa and upper Colorado rivers (Archer et al. 1985; Karp
and Tyus, in review). The razorback sucker persists in the lower Yampa and
Green rivers, the mainstream Colorado River, and the lower San Juan River,
but there is little indication of recruitment in these remnant populations
(McAda and Wydowski 1980; Meyer and Moretti 1988; Lanigan and Tyus 1989; Tyus
and Karp, in review). Bonytail chub are extremely rare in the upper Colorado
River basin (Valdez and Clemmer 1982; U. S. Fish and Wildlife Service 1987a).
All four fishes have been extirpated in the Green River between Flaming Gorge
Dam and the Yampa River confluence, presumably due, in part, to the loss of
usable habitat following closure of the dam (Vanicek et al. 1970). The Yampa
River supports all of its native fish fauna including self-sustaining
populations of some of the rare species and is considered important to the
maintenance and availability of usable rare fish habitat in the downstream
Green River (Tyus and Karp 1989).
Study Abstracts
The following section abstracts all reports completed under the Flaming
Gorge Interagency Agreement of 1986. These reports are generally organized
under the appropriate study; however,-there was some overlap between study
reports. Abstracts were taken from each respective report.
Study 1: Summer and Fall Requirements of Age-0 Colorado squawfish in the Green
River.
Report 1- Distribution, Abundance, Habitat use, and Growth of Young Colorado
squawfish in the Green River Basin, Colorado and Utah (Tyus and Haines, in
review).
Age-0 Colorado squawfish Ptychocheilus Lucius (N = 11,378) were captured
in drift nets and seines in the Green and Yampa rivers 1979-1988. Larvae were
captured in stream drift (N = 601) in June and July, and small postlarvae were
captured in shoreline habitats (N = 3,079) in July and August. The young fish
appeared in drift nets about 47 d after the peak spring discharge, and
thereafter for about 2-6 weeks. Larval Colorado squawfish moved downstream
soon after hatching. By autumn, postlarvae were most abundant (N = 6,459) in
lower gradient reaches of the Green River, about 150 km below the Yampa River
spawning area (River km (RK) 335-450); and about 130 km below the Green River
spawning area (RK 50 -160). Postlarvae were most abundant in shoreline
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