7166

• UCREFRP Catalog Number: 7166
• Author: Miller, W. H., et al.
• Title: Yampa River Fishes Study
• USFW Year: 1982.
• USFW - Doc Type: Final Report.
• Copyright Material: NO

squawfish, although rare, were found in all strata except Stratum 3 on
the Yampa. A total of 64 adult Colorado squawfish were captured in the
Yampa, and 15 in the Green River. Adult Colorado squawfish demonstrated
some specific microhabitat preferences, but there was no correlation
evident between the PHABSIM modeled weighted useable area curves and
adult squawfish distribution.
Seven adult Colorado squawfish in the upper Yampa River and one in
the Green River at Echo Park were implanted with radiotransmitters and ti
monitored. All seven radiotagged Yampa River fish and one Green River
fish migrated into the lower Yampa River in early July. Additionally,
4nother,36 ripe Colorado squawfish, including 2 recaptures, were col- y
lected in the lower Yampa between 1 July and 9 July 1981 during radio-
tracking and spawning studies. This spawning migration had been post-
ulated by several researchers, but never documented. Total distance
moved during June and July by each of the 8 radiotelemetered squawfish
ranged from 88 to 350 km.
Colorado squawfish spawned in the Yampa River during the 1 July to
9 July period during 1981. Further documentation of Colorado squaw.fish
spawning in the lower Yampa (and possibly in the Green) was provided by
collection of young-of-the-year fish from the lower 12 mi of the Yampa,
and below Split Mountain on the Green. These collections indicated a
drift behavior whereby larvae actively drift downstream away from the
harsh environment of the spawning site to more favorable quiet backwater
habitats. Identification and protection of larval nursery areas and
long distance,spawning migrations of adult Colorado squawfish may be the
most significant factors for preservation of this endangered fish.
Habitat selected by Colorado squawfish for spawning in the lower
Yampa River appears to be: 1) water of medium depth, 3 to 7 ft; 2) low
velocity of 0 to 2.8 ft/s and averaging 1.2 ft/s; and 3) substrate of
the lower cobble/rubble size with mean diamter of 7.5 cm. The association
of adjacent deep pool areas and the mix of various habitats is also
believed to be significant. Using the PABSIM modeling process it was
concluded that flows in the lower Yampa River, below the confluence with
the Little Snake River, in the 800 to 2,000 cfs range provided the
highest Weighted Useable Area (WUA) for Colorado squawfish spawning.
The humpback chub, though extremely rare, was collected in the
lower Yampa Canyon and in Whirlpool Canyon on the Green River. Addi-
tional studies are needed to evaluate the significance of these col-
lections. The bonytail chub formerly occurred in DNM but was not col-
lected in the current study and appears to be extinct above Split
Mountain. Razorback sucker was collected in low numbers in spawning
condition from the Green River and lower Yampa River study area only in
May and June. Though spawning activities probably occurred, success of
such attempts is doubtful since no young or juvenile razorback suckers
have been collected in 3 years of intensive sampling on the Green
River.
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