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

to 1.37 m, and mean column velocity of 0 to 0.3048 mps. ...The areas used by
the fish (razorback sucker) were characterized by average water depth of
0.6096 to 1.37 m, and mean column velocity of 0.03 to 0.335 mps.
Overwintering adult Colorado squawfish rested in midchannel slow runs and
slackwaters and fed in eddies and backwaters. Average gross movement rate of
adult Colorado squawfish in eddies and backwaters (48.20 m/h) was
significantly greater than in slow runs and slackwaters (21.71 m/h),
indicating a foraging behavior in the former habitats and a resting mode in.
the latter. These observations suggest that overwintering adult Colorado
squawfish rest in deep midchannel habitats with low velocity and feed in
shoreline eddies and backwaters.
...Significantly greater local movement was exhibited by adult Colorado
squawfish and razorback suckers exposed to fluctuating river levels that
exceeded 5 cm/h. ...Microhabitats used by these fish were altered or shifted
by the fluctuating flows, causing the fish to move. We concluded from these
observations that flow fluctuation rates greater than 5 cm/h caused about i90
percent greater movement in adult Colorado squawfish and 39 percent greater
movement in adult razorback suckers.
Movement of adult Colorado squawfish and razorback suckers under
fluctuating flows was increased when shifting and floating ice masses occurred
during periodic breakups. ...A subsequent increase in flow often dislodged
and transported the ice downstream, causing fish to move to dodge the ice
masses. Thus, maximum flow fluctuations caused ice buildup and transport in
January and February and caused additional movement by the radiotagged fish.
...Flow fluctuations of sufficient magnitude to cause fish to move
extended as far downstream as Bonanza Bridge, about 192 km downstream of
Flaming Gorge Dam. We concluded that these adult endangered fish in the upper
88 km of their distribution in the Green River can be expected to move more
frequently than fish further downstream in order to remain in suitable
microhabitat. The effect of this energy expenditure on survival, growth, and
reproductive potential is unknown.
Flow release scenarios from Flaming Gorge Dam ... of 22.64 m3/s followed
by a maximum release of 118.86 m3/s for 8 hours resulted in a stage change,
sufficient to cause fish movement as far downstream ~s the Bonanza Bridge,-192
kr~ from Flaming Gorge Dam. A flow release of 22.64 m3/s followed by 118.86
m /s for 4 hours resulted in a stage change rate of 5 cr~/h or greater as far
downstream as Jensen. Flow release of 22.64 to 118.86 m /s for 2 hours did-not
produce a stage change rate greater than 5 cm/h within the current known
distribution of adult Colorado squawfish and razorback suckers (abstracted
from Summary of Findings).
Report 4- Winter Habitat Use of Young Colorado squawfish (Tyus, in prep.}
Shoreline habitats and general river conditions were studied during the
winters of 1987-88 and 1988-89. Weather conditions differed between. the two
winters, but ice cover generally formed by mid-December. Few fish were
captured using baited minnow traps, but 5 young Colorado squawfish were
collected in one backwater in December 1987 and one hatchery-reared juvenile.
razorback sucker was captured in 1988. fluctuating flows in 1987-88 caused
shoreline scouring in the Jensen area by moving blocks of ice, and alternate
flooding and dewatering of low-lying areas at Ouray due to ice jams. Lower,
more stable flows in 1988-89 resulted in shallower backwaters but less
shoreline scouring (Preliminary abstract).
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