9520

• UCREFRP Catalog Number: 9520
• Author: Haines, G. B., D. Irving and T. Modde.
• Title: White River Base Flow Study for Endangered Fishes, Colorado and Utah, 1995-1996.
• USFW Year: 2004.
• USFW - Doc Type: 5D,
• Copyright Material: NO

of riflle and run habitats; that the pool and eddy habitat were secondary components of main

channel riflle and run habitats; that habitat proportions remained relatively constant from 600 to

150 cfs; and that riflle habitat increased in proportion to the other habitats when flows dropped

below 150 cfs.

In the Yampa River, adult Colorado pikeminnow apparently used different habitats during

day and night (Miller and Rees, 1997; Miller and Modde, 1999). In daylight the fish remained in

pools or deep runs> 1.2 m. After sunset, fish moved to feeding areas, primarily riflles, and were

very active. Miller and Modde (1999) pointed out that base flow management should address

both resting and active behaviors and focus on the most limiting flow for habitat needs.

Our simulations of daytime resting habitat for the White River indicated that the

availability of quality habitat was low, because depths> 1.2 m were relatively rare in the White

River, even at flows greater than base flow. The Colorado pikeminnow in the White River

apparently found suitable daytime resting areas in habitats with depths much less than 1.2 m.

Simulations of night foraging habitats showed a linear increase with flow and therefore no

curve break to identify a minimum flow below which habitat was lost at an increasing rate.

Osumundson (2001) found that habitat use by adult Colorado pikeminnow varied

seasonally. In the winter they favored low-velocity habitats like pools and backwaters; in the

spring, when water velocities were high and main-channel temperatures low, they tended to use

warm off-channel, low-velocity sites, like backwaters and flooded gravel pits; and in the summer

use increased in runs and eddies and pools and backwaters remained important.

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