1106

• UCREFRP Catalog Number: 1106
• Author: Gosse, J.
• Title: Microhabitat of Rainbow and Cutthroat Trout in the Green River Below Flaming Gorge Dam.
• USFW Year: 1982.
• USFW - Doc Type: Logan, UT.
• Copyright Material: NO

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Summary

The development and use of tolerance intervals is suggested

as an al ternative to probabil ity-of-use curves for model ing ap-

plications. For the rainbow and cutthroat trout in the Green

River, accurate modeling requires data stratification by species,
life stage, activ.ity, and season. It is important that predic-
tive models provide accurate velocities at the depths occupied by
the fish rather than using average column velocities.
For the activity of stationary swimming, fish velocity tend-
ed to increase and fish depth tended to decrease with increased
flows. For the activity of random swimming, fish often moved
along with changes in sheer edges as flows changed with little
..---
resultant change in fish velocity.
There was a large difference between winter and summer dis-
tribution of the trout and in the importance of the two activi-
ties. Glides and rapids were the primary habitat for trout in
the summer. During the winter, fish were heavily concentrated in
..
a few large pool s. Random swimming was observed infrequently
during summer but was common during winter.
Present low flow levels were the upper limit of plant bed
establishment. Plant beds were important in producing high in-
vertebrate biomass, especially Gammarus.
During the pre-test period in January 1982, trout occupied
habitats very similar to those occupied during January 1981.
Juvenile cutthroat trout were located higher in the water column
than the other life stages in 1982 and were physically isolated