9314 ‎(2)‎

• UCREFRP Catalog Number: 9314
• Author: Wick, E. J. and J. A. Hawkins.
• Title: Colorado Squawfish Winter Habitat Study.
• USFW Year: 1989.
• USFW - Doc Type: Fort Collins.
• Copyright Material: NO

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SLHAARY
Radiotracking of adult Colorado squawfish (Ptychocheilus lucius) was
conducted on the upper Yampa River, Colorado, over two winters (Decker 1986-
March 1988) under conditions historically found in the upper portions of the
Colorado River Systm. During Winter 1, 10 squawfish were radiotracked for
590.8 total observation hours, from which 118 hours were used to develop
habitat utilization criteria. During the fall and winter of the second year,
74 observation hours were accumulated on 10 squawfish. Of these, 34 hours
were used to develop winter habitat utilization criteria on depth, velocity
and substrate. Squawfish were often active within a particular habitat but
they did not move outside the river reach they selected for over wintering.
Squawfish shored fidelity to very specific habitat areas by remaining in
either one or a few favorite habitats throughout the winter. During the ice
covered period, total range of movement of all fish averaged only 0.3 miles
each year. several squawfish deaonstrated fidelity to specific fall and
winter habitats and river reaches over one or more years. During winter 1,
embayment, backwater, and run habitats were most frequently used. Pool and
run habitat were used most often in Winter 2. Habitat use also differed
between the three study areas. This appeared related to habitat availability
and diversity. A backwater habitat was used almost exclusively by three fish
in the GOVeri'riTlent Bridge study area, river mile (M) 95-100, during Winter 1.
Run habitat was used most frequently the next year probably because channel
bed changes prevented access to the area used most frequently in Winter 1.
Embayment and run habitat appeared to be preferred over pool habitat in the
Maybell study area (RMI 70-82) which had diverse habitat availability. Pool
habitat was used almost exclusively in the Lily Park study area (IM 51-54),
in Winter 2, where pool habitat was dominant. Effective depth (ice free water
under packed frazil and/or solid ice cover) and velocity utilization for each _
trip were averaged over the winter period for three habitat categories.
Shallowest mean effective depths (2 feet) and velocities [0.1 feet/second
(ft/s) ] were from backwater and embayment habitats. Eddys and pools had the
deepest average effective depth utilization (3.3 feet) with an average mean
velocity of 0.2 ft/s. The run and shoreline habitat category had the highest
average velocity (0.5 ft/s) with an average effective depth of 2.4 feet.
Naturally stable flow conditions allowed ice cover to exist throughout the
majority of the winter period both years. Flaws and air temperatures were
above normal in winter 1 and below normal in Winter 2.
. Formaticn of different types of ice on the Yampa River changed hydraulic
conditions. During early winter, water surface elevations were maintained in
spite of reductions in discharge. During Winter 2, changes in effective
depths used by squawfish were examined at the Maybell study site by comparing
elevation changes of water surface, ice surface, and ice thickness in response
to changes in discharge. Discharge increased tthout most of Winter 2, a
relatively low water year, ranging from 142 cfs on December 15, 1987 to 340
cfs on March 3, 1988. Ice thickness increased from 0.85 feet December 15,
1987 to 2.12 feet March 15, 1988. Increasing water surface elevations
compensated for increasing ice thickness resulting in relatively stable
effective depth. Effective depths measured biweekly in embayment habitat
between December 15 and February 17 varied only 0.1 feet. Regression analysis

of discharge on water surface elevation was used to predict the effect of ,
hypothetical reductions in flaw below the lowest measured discharge of 142
cfs. For each 20 cfs loss in discharge, water surface elevation was predicted
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