7300

• UCREFRP Catalog Number: 7300
• Author: Tyus, H. M. and C. A. Karp.
• Title: Habitat Use and Streamflow Needs of Rare and Endangered Fishes, Yampa River, Colorado.
• USFW Year: 1989.
• USFW - Doc Type: Biological Report 89‎(14)‎,
• Copyright Material: NO

Colorado squawfish vary with time of year, and that both
reproduction and recruitment to the juvenile stage are
highest in years when hydrographs approximate natural
flow conditions. This presumably is related to the
availability of nursery backwater habitat in fall.
Aerial photography was used to evaluate the effect of
seven test flows on availability of backwater habitat in late
summer and fa111987 at four sites (Island Park, Jensen,
Ouray, Sand Wash) in the upper Green River (M.
Pucherelli and R. Clark, written communication). It was
found that the greatest amount of backwater habitat
resulted when flows ranged from 31.15 to 50.17 m3/s, and
the least amount of backwater habitat was present at flows
of 68.57 and 148.85 m3/s. Averaging the Jensen, Ouray,
and Sand Wash sites (i.e., the upper Green River
concentration area for young Colorado squawfish drifting
out of the Yampa River), area of backwater habitat was
greatest with flows of 50.17 and 47.74 m3/s, and number
of backwater habitats was maximized at 47.74 m3/s. These
relations support the biological information and
emphasize that young Colorado squawfish need low flows
in late summer and fall.
Juvenile
Factors limiting the distribution and abundance of
juvenile Colorado squawfish are difficult to assess
because there is little information available regarding
their habitat requirements. Stream blockage is viewed
as limiting because upstream movement of juveniles is
necessary to maintain adult populations.
Evidence of predation by nonnative fishes in both
artificial and natural environments suggests that this
factor limits the survival of juvenile Colorado squawfish.
Hendrickson and Brooks (1987) noted predation by
yellow bullhead (Ictalunis rratalis) and largemouth bass
(Micropterus salmoides) on young Colorado squawfish
stocked into the Verde River, Arizona. Osmundson
(1987) noted predation by largemouth bass, green
sunfish, black crappie (Pomoris -iigromaculatres), and
black bullhead (Ictalunrs melas) on young Colorado
squawfish in gravel pits near the Colorado River,
Colorado, and indicated that predation by channel
catfish may also have occurred. In addition, Coon
(1965) reported channel catfish predation on Colorado
squawfish in the Dolores River. Flow regimens and
other conditions that may aid the proliferation of these
nonnative predators must be identified and, if possible,
avoided.
Humpback Chub
Spring peak flows are important to reproductive
success of the humpback chub, because spawning
occurs in shoreline eddy habitat shortly after this period.
Availability of these habitats is greatest during spring
runoff and lessens thereafter with decreasing summer
flows (Karp and Tyus 1989). Loss or reduction of spring
runoff could reduce availability of spawning habitat and
thus adversely affect humpback chub reproduction.
Habitat alteration may also promote hybridization with
other species (Valdez and Clemmer 1982). Flow
reductions- and decreased temperatures have been
implicated as factors curtailing successful spawn and
increasing competition in the Colorado River (Kaeding
and Zimmerman 1983).
Humpback chubs and channel catfish may be
competing for food or quality microhabitat as suggested
by capture of both species with baits in the same eddy
habitats in the Yampa River (Tyus and Minckley 1988;
Karp and Tyus 1989). The high number of channel
catfish in preferred humpback chub spawning habitat
(30% of the catch in 1987 and 1988; Karp and Tyus 1989)
suggests that this omnivorous introduced species may
adversely affect reproductive success of the humpback
chub in the Yampa Canyon. In addition, the presence of
bite marks on humpback and roundtail chubs may be
due to attempted predation by channel catfish (Kaeding
and Zimmerman 1983; Karp and Tyus 1989; C. O.
Minckley, personal communication). W. L. Minckley
(personal communication) also noted humpback chub
remains in stomachs of channel catfish captured in the
Little Colorado River. Flows or other conditions (e.g.,
temperature; Tyus and Nikirk, in review) which may
favor growth of channel catfish in the Green River basin
should be determined and avoided.
Humpback chubs predominantly use canyon habitat
(Fig. 4) and availability of such habitat could be
adversely affected by alteration of the natural flow cycle
of the Yampa River (Fig. 1).
Bonytail Chub
Bonytail chubs were never reported as abundant in
the Yampa River and a decline is not indicated in that
system. However, in the Echo Park area, bonytail chubs
have apparently declined, possibly due to flow and
temperature changes resulting from closure of Flaming
Gorge Dam. A similar pattern has been noted in the
Colorado River downstream from Glen Canyon Dam
(Utah State Department of Fish and Game 1964,1969).
Although the preimpoundment poisoning of riverine
habitat in the upper Green River in 1962 has been
implicated in the decline of the bonytail chub in that
system, fish collections in DNM before and after the
poisoning (Binns et a1.1963; Vanicek and Kramer 1969;
Vanicek et al. 1970) suggested that the downstream
extent of the poison was not a factor in the almost total
extirpation of the species from the Echo Park area.
Current negotiations between the Fish and Wildlife
Service and Bureau of Reclamation regarding
management of Flaming Gorge Dam operations for rare
fishes may improve the future of the bonytail chub in the
21