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

backwaters that were relatively warm (19.4°C in one area, 14.6°C in the
other), deep (33.9cm, 41.8cm), large (494m2, 1,158m2) and turbid. Abundance
and size of young Colorado squawfish were inversely correlated with abnormally
high summer flows released from Flaming Gorge dam, which inundated backwater
nursery habitats. Backwater sampling in autumn and the fol]owing spring (1985-
86, 1987-88, and 1988-89) indicated that overwintering mortality of age-O fish
was not a major factor affecting recruitment of Colorado squawfish in the
Green River (Preliminary Abstract).
Report 2- Diel Movements and Habitat Preferences of Young Colorado squawfish
(Tyus, in prep).
Young Colorado squawfish (N=1,127) were captured, fin-clipped, and
released in the Green River of Utah in April, October, and November, 1980-81.
Recaptures of 23% of the fish demonstrated extensive diet movements between
backwaters and other shoreline habitats. The young fish were most abundant in
backwater habitats in afternoon when water temperatures were highest (>i0°C),
and virtually absent in them at dawn when temperatures were lowest (<10°C).
The most abundant fish species collected with the young Colorado squawfish
were the red shiner Notropis lutrens_is and fathead minnow Pimephales promelas,
and numbers of these fishes a7 so varied with temperatures and time of day
(Preliminary Abstract).
Study 2: Winter Habitat and Flows for Adult and Young Colorado squawfish, and
Adult Razorback Sucker.
Report 3- Winter Habitat Study of Endangered Fish-Green River. Wintertime
Movement and Habitat of Adult Colorado squawfish and Razorback Suckers
(Valdez and Masslich 1989).
Adult Colorado squawfish and razorback suckers in the Green River
overwintered in specific regions, general]y less than 4.8 km long. Maximum net
movement by an adult radiotagged Colorado squawfish during year 1, {December
1, 1986 through March 31, 1987) was 35.52 km upstream. Seven of the ten
radiotagged Colorado squawfish remained within a 4.8 km reach of river.
Maximum net movement during year 2 (1987-88) was 41.44 km downstream. Eight
of the nine fish remained within a 3.2 km reach. We conclude from these
observations that the majority of overwintering adult Colorado squawfish
remained with a 3.2 to 4.8 km reach of the river.
Maximum net movement by an adult radiotagged razorback sucker during-the
first winter period was 16.8 km downstream. Six of the eight radiotagged fish
remained within a i.6 km reach of the river. Maximum net movement during the
second winter period was 11.68 km upstream. Six of the nine fish remained
within a 4.8 km reach. We conclude from these observations that the majority
of overwintering adult razorback suckers remained within a 1.6 to 4.8 km reach
of river.
Overwintering adult Colorado squawfish and razorback suckers exhibited
local diel movement ... the majority of overwintering adult Colorado squawfish
moved at rates of 15-23 m/h within an occupied habitat in ice-free water, and
about 29 m/h under stable ice. ...The majority of overwintering adult
razorback suckers moved at-rates of 25-31 m/h within an occupied habitat.
Overwintering adult Colorado squawfish and razorback suckers .selected -.
specific microhabitat within low. velocity habitats. ...The areas used by the
fish (Colorado squawfish) were characterized by average water-depth of 0.762