7346

• UCREFRP Catalog Number: 7346
• Author: Wick, E. J. and J. A. Hawkins.
• Title: Colorado Squawfish Winter Habitat Study, Yampa River, Colorado 1986-1988.
• USFW Year: 1989.
• USFW - Doc Type: Fort Collins, Colorado.
• Copyright Material: NO

Depti, velocity, and substrate utilization
Number of observations for total depth, effective depth, and velocity '
were normalized for each year within each habitat type during the winter.
Total depth reflected distance from the river bottom to the top of the ice;
this measurement included solid ice, packed non-moving frazil, and water
(effective depth).
Backwater habitats showed the narrowest range of depths used, and pool
habitat showed the broadest range and deepest depths. Generally, the
;
difference between total depth and effective depth reflected surface ice
thickness except in run and pool habitat where effective depth was
substantially less due to very thick (packed) frazil ice. Highest frequency
of use for total depths was 2.0-3.5 feet in backwater, embayment, run, and
shoreline habitats. Frequency of effective depth use was highest between 1.0
to 2.0 feet. 'Dotal depths used most frequently in eddy habitat ranged 5.0 to
9.5 feet. Effective depths used most frequently in eddy habitat ranged
between 3.5 to 9.0 feet. In pool habitat the most frequently used total depth
the most frequently used effective depth was 3.0 feet,
was 10.0 feet; however
,
showing the effect of packed frazil ice (Figures 11 and 12).
The predominant velocity within backwater, embayment and eddy habitats
during the winter was 0.0 ft/s, but a few velocities over 0.0 ft/s indicated
fish locations along the interface with the main channel. The positive
velocities within eddy habitat indicate fish within the eddy-run interface.
The greatest range and highest velocity were found in run habitat. Velocities
used most in run and shoreline habitat were 0.0 to 0.4 ft/s. The most
frequently used velocity in pool habitat was 0.6 ft/s (Figure 13). These
velocities are not fish nose velocities but are mean column velocities taken
at 0.6 effective depth. Fish may be utilizing micro-habitats that provide
lower velocities. Depth and velocity summaries over extended periods can be
misleading because a large number of observations on any given trip or period
can heavily influence the over-all frequency. Therefore, depth and velocity
are presented below on a trip by trip basis to better reflect habitat use aver
time.
Most depth mats during the fall period were in ice-free water.
Depth measurements which included ice are identified within the appropriate
figures. Ice thickens during this time was 0.1 foot. Water depth in
backwaters during the fall were between 3.0 and 4.0 feet. Embayment use was
similar except for use of shallower 1.5 foot depth. Fish use of the
shallowest depths in each habitat may have been facilitated by ice that
provided overhead cover. Depth of eddy habitat was greatest at 4.0 and 4.5
feet. Pool depths showed a bimodality at 5.0 and 13.0 feet. lam and
shoreline depth utilizations ranged between 3.0 and 4.5 feet (Figure 14). Fall
velocities. were mostly 0.0 ft/s in backwater, embayment, eddy, and pool .
habitats and 0.5 ft/s in run habitat and 0.3 ft/s in shoreline habitat (Figure ?
15).
Winter substrate use was segregated by habitat type for each year of the
study (Table 7 and 8). of the 36 possible combinations of clay, silt, sand,
gravel, cobble, boulder, and bedrock substrates, 21 were observed throughout
the 2 years of the study. Sand (SASA) was the most commonly used substrate
type in both years of the study. It was the dominant substrate used in run
habitat during Winter 1 and in run and pool habitat in Winter 2. During
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