9569

• UCREFRP Catalog Number: 9569
• Author: Valdez, R. A.
• Title: Synthesis of Winter Investigations of Endangered Fish in the Green River Below Flaming Gorge Dam.
• USFW Year: 1994.
• USFW - Doc Type: 18-11,
• Copyright Material: NO

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16 months later, on February 19, 1988, about 2 kIn downstream. Valdez and Masslich

(1989) suspected that other adult razorback suckers and Colorado squawfish would have

been relocated at specific wintering sites, had the radiotransmitters lasted a full year.

Adult razorback suckers, like adult Colorado squawfish, were locally active throughout

winter. Movement was typically within a given habitat (e.g., slow run or slackwater),

between several favorite spots. Local movement by overwintering razorback suckers was

characterized by rates of 25 and 31 m/hr, for Winter 1 and Winter 2, respectively. This

movement was usually between microhabitats that the fish occupied for extended periods

of time. One fish (#OR-3257) monitored for 24 hours occupied three spots for periods of

15, 4, and 5 hours (Figure 13). The fish moved a total of 103 m, with net displacement of

only 20 m from the original location. These movement rates were considered normal, and

did not differ with habitat types, as with Colorado squawfish, i.e., greater movement by

squawfish in backwaters was attributed to foraging for small fish prey.

Habitat Use

Colorado Squawtish

Habitat used by radiotagged adult Colorado squawfish in the two winters (1986-87

and 1987-88) differed in both the Green and Yampa rivers (Figure 14). Different habitat

use for Green River fish was attributed to flow and ice conditions (Winter 1 with high flow

and no ice, Winter 2 with low flow and ice), and different use by Yampa River fish was

attributed to flows (Winter 1 with high flow, Winter 2 with low flow). The Yampa River was

ice-covered from early December to early March of both winters.

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