9350

• UCREFRP Catalog Number: 9350
• Author: Hawkins, J., T. Modde and J. Bundy.
• Title: Ichthyogauna of the Little Snake River, Colorado, 1995 with Notes on Movements of Humpback Chub.
• USFW Year: 2001.
• USFW - Doc Type: Denver.
• Copyright Material: NO

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DISCUSSION

Discharge, water temperature, and water quality

The 1 995 water year exemplified the seasonal nature and extreme variability
of the Little Snake River. Annual runoff volume in 1995 was 1.5 times higher than
the average of 415,200 acre feet lCrowfoot et al. 1996) and three times wetter
than the previous year which discharged about half the average volume (Ugland et
aJ. 1995). The unregulated characteristics of the river and the nature of the
hydrograph in 1995 were represented by the extreme peak to base-flow ratio
(165: 11 primarily caused by extremely low base flows which are typical for the
Little Snake River. Low baseflow dewatered all reaches but was most evident in
the sandy and braided middle reach. Fish habitat was maintained in the lower and
upper reaches by scattered refugia pools, connected with minimal surface flows
that were very shallow and created a barrier to fish movement between pools.
Shallow, widely dispersed flows also had a tremendous influence on water
temperature and caused diel variations of a greater magnitude than those in the
Yampa River. These and other physical influences likely caused a significant, but
unknown, role in initially attracting and eventually repelling humpback chub and
Colorado pikeminnow and structuring the fish community of the Little Snake River.

Fish community sampling

Humpback chub and Colorado pikeminnow occupied the lower 15 km of the
Little Snake River during summer runoff. Locations and dates of their capture in
1995 matched those of previous collections of these species lMiller et al. 1982,
Wick et al. 1 991), demonstrating that both species use the Little Snake River on a
regular basis. We found no evidence of their occurrence in the middle or upper
reaches even though a Colorado pikeminnow was previously captured at about