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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or activity. Fish often moved closer to the stream bottom as

flows increased, especially for the activity of stationary swim-

ming and during the summer. The average mean column velocity was

consistently higher than fish velocity for the activity of sta-

~ tionary swimming. This resulted from the fact that fish were lo-

cated below the water depth where mean co1 umn vel oc i ti es are

measured.

Mean velocities for the activity of random swimming

were lower than mean velocities for stationary swimming.

On five occasions, fish were observed during prearranged

flow changes. Stationary swimming fish often moved closer to the

bottom as flows increased and farther fr:om the bottom as flow de-

creased.

In some cases, juveniles were observed to move closer

.r to shore as flows increased. Feeding rates often increased with
increasing flow.
The low water line was the upper limit for establishment of
aquatic plants. Water velocities (near the bottom) and substrate
both appeared important in determining which species of plant was
4r found in an area. Plant beds on silt substrate consistently had
higher densities of invertebrates than the other substrate types.
During the pre-test period in January 1982, fish were ob-
served to choose microhabitat similar to that chosen in January
1981. They were clumped in essentially the same pools as they
had occupied the previous year.
During January 1982, juvenile cutthroat were located higher
in the water column than the other groups of fish. The juvenile
cutthroat trout were physically more isolated from the other
groups than they were during January 1981.

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