7047

• UCREFRP Catalog Number: 7047
• Author: Tyus, H. M. and C. A. Karp.
• Title: Habitat Use and Streamflow Needs of Rare and Endangered Fishes in the Green River, Utah
• USFW Year: 1991.
• USFW - Doc Type: Final Report.
• Copyright Material: NO

lower Green River (km 0-211) were extremely rare; their numbers were too small
(13 fish captured, 1 recaptured) to allow a reliable population estimate. Gray
and Desolation canyons separated the upper and lower Green River razorback
sucker populations. These canyons and a low diversion dam appeared to be
barriers to fish movement. The absence of the razorback sucker in Gray and
lower Desolation canyons (km 211-282) suggested a lack of suitable habitat.
The Green River supports the largest known population of razorback suckers
among the species' native riverine habitats. However, low population density
and recruitment, as well as habitat alteration, mandate increased research and
management efforts to save this population. (Abstract)
Report 8- Spawning and movements of razorback sucker, ~rauchen texanus, in
the Green River Basin of Colorado and Utah. (Tyus and Karp 1990)
Spawning and movements of the razorback sucker, Xvrauchen texanus, were
evaluated by radiotelemetry (n=17 fish) and capture of 230 adults (105
recaptures) in the Green and Yampa rivers, 1987-1989. Ripe fish (n=194) were
captured in riffles with cobble, gravel, and sand substrates from mid-April to
early June. Recaptured males were ripe from 2 to 28 days and recaptured
females from 2 to 15 days. Razorback suckers spawned during ascendin~ and
highest spring flows at water temperatures of about 14°C (range 9-17 C].
Spawning migrations of 30-106 km were detected in 17 razorback suckers, but
movements were more limited or undetected in other individuals. Flooded
lowlands and lower portions of tributary streams presumably served as resting-
feeding areas for razorback suckers during the breeding season. Native
flannelmouth sucker, Catostomous latiuinnis, bluehead sucker, C. discobolus,
and putative flannelmouth X razorback sucker hybrids in breeding condition
were collected with ripe razorback suckers. Razorback sucker is in peril due
to a paucity of spawning adults, hybridization with other suckers, little or
no recruitment, and habitat loss. (Abstract)
Report 9- Humpback chub (Gila yaha) in the Yampa and Green Rivers, Dinosaur
National Monument, with observations on roundtail chub (G. robusta)
and other sympatric fishes. (Karp and Tyus 1990a)
We evaluated distribution, habitat use, spawning, and species
associations of the endangered humpback chub (Gila c ha in the Yampa and
Green rivers, Dinosaur National Monument, from 1986 to 1989. Adult and
juvenile humpback chub were captured in high-gradient reaches of Yampa and
Whirlpool canyons where they were rare (N=133, < 1% of all fish captured). The
fish were primarily captured in eddy habitats in association with 7 native and
12 nonnative fish species. Roundtail chub (G. robusta) were widely distributed
in eddies, pools, runs, and riffles. Humpback chub (N=39) and roundtail chub
(N=242) in reproductive condition were sympatric in eddy habitats during the
5-6 week period following highest spring runoff. River temperatures at this
time averaged about 20°C. Nonnative channel catfish (Ictalurus punctatus) were
abundant in eddies yielding humpback and roundtail chubs, suggesting a
potential for negative interactions between the native and introduced fishes.
(Abstract)
Report 10- Age determination in Colorado squawfish and razorback sucker.
(Minckley et al., in prep.)
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