9690

• UCREFRP Catalog Number: 9690
• Author: Recovery Implementation Program
• Title: Recovery Implementation Program For Endangered Fish Species In The Upper Colorado River Basin 23rd Annual Recovery Program Researchers Meeting
• USFW Year: 2002
• USFW - Doc Type: 21
• Copyright Material: NO

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ABSTRACTS

Instream Flow

Anderson, R.

Colorado Division of Wildlife, Grand Junction, CO

Progress on Colorado Division of Wildlife instream flow recommendations for the Colorado
River (l5-Mile Reach) and the Yampa River, with updates for smallmouth bass and catfish
in the Yam pa. Two-dimensional modeling of five study sites is being used to quantify native fish
habitat availability over a range of low flows on the Colorado and Yampa Rivers. Habitat
mapping has been completed at one site on the Colorado River (Com Lake) and one site on the
Yampa (Duffy) and is progressing (contract with USU) for the remaining 3 sites. 2-D modeling
results show strongly different habitat composition between Duffy and Com Lake and fish
sampling results show strongly different fish population characteristics. At typical base flows (100
- 150 cfs), Duffy is dominated by shallow low- velocity habitats while the Colorado River is
primarily rifile or fast run habitats at typical base flows (1000-1500 cfs). Between 1998 and 2001,
fish density estimates averaged 384 fish per kilometer at Duffy and 3,993 fish per kilometer at
Com Lake ( Colorado, River). Native fish are very rare in the Yampa' s Duffy reach, but are
abundant in the Colorado's IS-Mile Reach. This appears to be a function of the habitat availability
at the two sites. Also it appears that habitat availability for native fish was further reduced in the
Yampa (Duffy and Sevens) during low flow years. Density for all native fish (flannelmouth and
bluehead sucker, roundtail chub, Colorado pikeminnow, speckled dace and mottled sculpin) in all
Yampa stations have displayed a strong to mild downward trend between 1998 and 2001.
Minimum flows in the Yampa River were much less in 2000 (30 cfs) and 2001 (50 cfs) compared
to 1997 (320 cfs), 1998 (116 cfs) and 1999 (166 cfs). Predation by northern pike may not have
been as significant in 2000 and 2001 as their numbers were much less than in prior years. In 2001,
smallmouth bass was the only species in the Yampa River to display large increases in abundance
for both yay and older fish. yay smallmouth bass counts for 2001 in the Duffy reach were near
4,000/station compared to 700/station in the earlier three years. Smallmouth bass for fish over 12
cm became the dominated species at Duffy for the first time. Also bass composition strongly
increased at Sevens and Lily Park in 2001. This suggests that habitat availability for bass increased
during low flow years. In contrast, density and composition of native fish in the Colorado River
have been stable between the higher (1999) and lower flow years (2000 and 2001).

Pitlick, J.

Department of Geography, University of Colorado, Boulder, CO

Update on Geomorphic Effects of Coordinated Reservoir Operations on Habitats in the
Upper Colorado River. This talk focuses on results from a 4-year study of the effects of
reservoir operations on sediment transport and channel change within the 15- and 18-mile reaches
ofthe Colorado River. Field studies have been done at several scales to assessthe movement of
coarse sediment on gravel bars, and the deposition of fine sediment in backwaters and other areas

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