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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Spring breakup was a critical period for fish in the Yampa River, as low-velocity

habitats became invaded by flowing water. Bed changes also occurred as sediment moved

with shifting currents. The Yampa River fish were noticeably more active during spring

breakup, also described by Wick and Hawkins (1989) as a violent event. Large slabs of ice

tilted and scraped along the river bottom, leaving dramatic changes in the channel bed, such

that a backwater at RM 95.7, was nearly filled with large amounts of gravel. Three

radiotagged Colorado squawfish that had occupied this backwater throughout winter, moved

to another downstream location. In contrast, radiotagged fish using an embayment at RM

81.1 remained in place, as very little ice was deposited and no changes were seen in the

embayment during breakup.

Movement And Habitat Of Radiota22ed Adults

Ten adult Colorado squawfish were radiotagged in each of two subsequent winters

in the Green and Yampa rivers, to monitor movement, local activity, habitat use, and

response to changing flows and ice conditions. Ten fish were monitored in the Green River

from December through March, 1986-87 (Winter 1), and ten different fish were monitored

from December through March, 1987-88 (Winter 2) (Valdez and Masslich 1989). Similarly,

ten adult Colorado squawfish were radiotagged and simultaneously monitored in the Yampa

River during each of the same time periods (Wick and Hawkins 1989). Ten adult razorback

suckers were also radiotagged and monitored in each of the two winters in the Green River.

Radiotagged fish were periodically located during regular monthly trips in the 4-

month winter period. Location, movement, and habitat use were recorded for each

relocated fish, and each fish was monitored for periods of one to several days to determine

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