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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local activity, and response to flow change and ice conditions. Movement and activity of the

Green River fish and the Yampa River fish (Table 3) are compared in the following

discussion.

Fish Movement And Activity

Colorado Sauawfish

Radiotagged adult Colorado squawfish moved relatively little during the two winters

obselVed in the Green and Yampa rivers. Common use of areas in winter, and return to

specific locations a year later suggests homing and fidelity for overwintering locations and

habitats in both rivers.

Average net movement (distance from first to last radio contact) of the Green River

fish was 9.0 kIn (n=10, range of 0.2-35.7 kIn) and 5.8 kIn (n=9, range of 0-41.7 kIn) during

Winter 1 and Winter 2, respectively. Excluding the fish with greatest movement, average

net movement was 6.0 kIn (n=9, range of 0.2-22.4 kIn) and 1.3 kIn (n=8, range of 0.0-3.2

kIn), respectively. Nearly 80 percent (15) of 19 fish monitored remained within 5 kIn of

their original location. Movement by the Yampa River fish under ice cover averaged 0.5 kIn

each year, with ranges of 0.0 to 1.8 km in Winter 1, and 0.0 to 0.8 km in Winter 2. Lesser

movement by the Yampa River fish may be explained by distribution of habitat in the two

rivers, and more stable flows and ice conditions. The Yampa River had distinct pools and

persistent off-channel habitats (e.g., backwaters, embayments), while the Green River was

dominated by runs with few persistent off-channel habitats, and daily fluctuating flows.

Movement by fish was greatest during ice break-up, as obselVed in March in both

rivers and periodically throughout winter on the Green River, with fluctuating dam releases.