7610

• UCREFRP Catalog Number: 7610
• Author: Wick, E. J. and J. A. Hawkins.
• Title: Colorado Squawfish Winter Habitat Study, Yampa River, Colorado, 1986-1987
• USFW Year: 1987.
• USFW - Doc Type: Final Report Year 1.
• Copyright Material: NO

r-
(Table it and Figures 24-26). The majority of shallow depths less than 1 foot
were from embayment habitat. In the backwater habitat at RMI 95.7 the most
commonly used depth was 2 feet. All depths greater than 6 feet were from eddy
habitat used by fish B07 at RMI 76.2 (Table 6). The high use of shale;Lhs
less than 1 foot c`uld have been due to ice cover. As previously mentioned the
overhead ice was probably a security facter allowing fish to venture into more
shallow water. Throughout most of the study the ice thickness ranged from 1
to 1.8 feet. If total water and ice depths (water elevation) were considered,
the averages would be at least a foot greater. Depth distributions f_U the
inner and outer holes were similar to the main a (Table 11 and Figures 27-
32). Inner hole depths were slightly shallower (X = 2.3) and outer hole depths
were deeper at 2.9 feet than main hole depths. The deep outer hole depths over
8 feet are all attributable to fish B07 in the eddy at RMI 76.2.
Velocity
Velocity histograms were based on measurements taken at 0.6 depth from
the bottom-of the ice (Figures 2a and 2b) and were made for the main, inner,
and outer holes. Main hole mean velocity was 0.21 feet/second and ranged from
0.0 to 1.9 feet/second (Table 12 and Figures 33-35). Inner hole velocity was
0.17 feet/second while outer hole velocity averaged 0.26 feet/second. The
range of short term data was from 0.0 to 2.2 feet/second while the highest
long term velocity was only 0.9 feet/second (Table 12 and Figures 36-41).
Substrate
Of the 36 possible combinations of clay, silt, sand, gravel, cobble, and
boulder substates, 19 were observed throughout the study (Figures 42-50).
Gravel-gravel (GRGR) was the most frequently utilized substrate followed by
sand-sand (SASA). The dominance of gravel-gravel (GRGR) is interesting since
many of the habitats in which it was dominant were 0.0 velocity backwater
areas (Table 8). The dominance of sand substrate in the short term data set is
probably related to the.dominance of run habitat.
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41

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Habitat
Overall, backwater was the most
run. Run was the most frequently used
(Figures 51-53).
commonly used habitat type followed by
habitat in the short term data set
40
Comparison of 2.5 vs 24 hour data
Long and short term data were often different. This could be due to
either differences in the sample designs or possibly fish reacting to observer
presence.
Short term observations would tend to create more data points, creating
smoother distributions for final analysis where long term observations tend to
stack data over a few data intervals, especially if fish remained at one site
for an extended time. Long term data is more subject to compounding observer
error. For instance, if a triangulation to a fish location is done incorrectly
it could lead to a heavy weighting of incorrect micro-habitat variables in the
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