1103

• UCREFRP Catalog Number: 1103
• Author: Holden, P. B.
• Title: Study of The Habitat Use and Movement Of The Rare Fishes In The Green River From Jensen To Green River, Utah, August and September, 1977
• USFW Year: 1977.
• USFW - Doc Type: Final Report.
• Copyright Material: NO

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Preferred Habitat of Rare Fishes

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Physical Components
River temperature varied considerably on a diel basis during this
study (Figure 2). Early morning temperatures were generally 3 to 5 C
cooler than late afternoon levels. Backwaters were the warmest areas9
often warming 3-8 degrees above that of the river proper in late after-
noon. Morning temperatures in the Jensen area in August were usually
15-17 C (River Mile 178). Morning temperatures in August in downstream
areas varied considerably with local weather conditions9 but weregener-
ally warmer (19-21 C) than those at Jensen. September temperatures in
Desolation Canyon (River Mile 30) were much colder (a low of 10.5 C)
due to the cool ambient air.
The level of the Green River in the study area fluctuates daily due
to releases from Flaming Gorge Dam. The greatest fluctuation occurred
at Jensen where a 16-inch daily rise and fall was noted. Diel fluctua-
tions in Desolation Canyon were only 3 to 4 inches. The large fluctua-
tion noted at Jensen caused a considerable daily change in available
habitat. Low flows provided a variety of habitat types9 especially back-
waters. High flows reduced the number of backwaters and generally cre-
ated a full channel situation (i.e., wetted area unbroken by sand bars,
etc.). In this area, juvenile squawfish were primarily caught either
during low river levels when backwaters were available, or in backwaters
which were not affected by the fluctuations.

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