9685

• UCREFRP Catalog Number: 9685
• Author: Tyus, H. M. and C. A. Karp.
• Title: Habitat Use and Streamflow Needs of Rare and Endangered Fishes
• USFW Year: 1989.
• USFW - Doc Type: Flaming Gorge Studies - 2nd Preliminary Draft.
• Copyright Material: NO

lower Green River (km0-211) 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, Xvrauchen texanus, in
the Green River Basin of Colorado and Utah (Tyus and Karp, in review).
Spawning and movements of the razorback sucker, Xvrauchen texanus, was
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 over a 4-5 week period each year between mid-April and early June.
Males remained in breeding condition for up to 28 days but females were ripe
for about one week. Razorback suckers spawned during ascendin~ and highest
spring flows and water temperatures of about 14°C {range 9-i7 C). Migrations
of 30-106 km to two spawning areas were detected in 17 razorback suckers, but
movements were more limited or undetected in other individuals. flooded
lowlands and mouths of tributary streams presumably served as resting-feeding
areas for razorback suckers during the breeding season. Native flannelmouth
sucker, Catostomous latipinnis, bluehead sucker, C. discobolus, and putative
flannelmouth X razorback sucker hybrids in breeding condition were also
captured with ripe razorback suckers in riffles with cobble, gravel, and sand
substrates. The razorback sucker is in peril due to a paucity of spawning
adults, hybridization with other suckers, little or no recruitment, and
habitat loss (Preliminary Abstract).
Report 9- Habitat Use, Spawning, and Morphology of Humpback Chub, in the Yampa
and Green Rivers, Dinosaur National Monument, Colorado and Utah (Karp and
Tyus, in review).
Habitat use and spawning of the endangered humpback chub Gila cypha was
evaluated in the Yampa and Green rivers, Dinosaur National Monument, 1986 to
1989. Humpback chub (n=133, 8% of a71 chub captures) were captured only in
whitewater canyon reaches dominated by rocky runs, and rapids, and were most
prevalent in shoreline eddy habitats. Humpback chub in breeding condition
(n=38) were captured at river temperatures of about 20°C during the period of
declining flows following peak spring runoff. Humpback chub were captured in
association with 18 other fish species, including 7 native and 11 introduced
forms. Co-occurrence of ripe humpback and ripe roundtail G. robusta chubs
indicated some temporal and spatial overlap in spawning, but incidence of
possible hybridization was judged low. Canyon habitats occupied by humpback
chub also supported large numbers of introduced channel catfish Ictalurus
punctatus, suggesting a potential for negative interactions between these
fishes. Humpback chubs were differentiated from roundtail and hatchery-reared
bonytail G. elegans chubs by-the presence of a fleshy snout and inferior
mouth, pronounced nuchal hump, deep and laterally compressed midsection,
indistinct squamation, and notable susceptibility to capture and handling .-
stress (Preliminary Abstract).
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