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

measured using a Marsh-McBirney Model 201 current meter. Negative velocity
was recorded if direction of current flaw deviated more than 90 degrees from
that of the main channel current. Substrate was identified visually or by
'feel' by probing with the depth rod. substrate was categorized as a
ccaabinaticn of primary and secondary couponents of clay, silt, sand, gravel,
cobble, or boulder. cover designations included vegetation, brush, and
boulder. '
Three sets of measurements were taken at each site; one set was at the
triangulated fish location (main site) with additional sets taken 1-2 m,
nine toward shore and "but" away from shore. Velocity measurements at the main

site were taken at 0.2, 0.6, and 0.8 depths from the water surface when ice '
free or from the bottom of the ice during ice cover. At the in and out
measurement sites, velocity was measured at 0.6 depth. During ice cover,
habitat measurements were taken through holes drilled in the ice. Boles were '
drilled using either an 8-inch strikemaster hand auger or 7-inch Strikemaster
gasoline powered auger. Additional measurements were then taken to determine
ice-free water depth (effective depth). These included solid ice thickness

(ice below the water surface in the hole), frazil ice thickness, and total '
depth (water depth in the hole). Water depth below the surface of the ice was
then calculated by subtracting ice thickness from total water depth (Figure

4). Tien frazil ice was present under the hard ice cover, its thickness was '
determined by lowering the velocity probe to the bottom, getting a positive
velocity reading, and then slowly raising the probe until the frazil could be
felt touching the probe and velocity decreased to 0.0 feet per second (ft/s).
The compact, non-moving, frazil ice deposits were treated as solid ice in
making water depth and velocity measurements (Figure 5). Winter discharge
measurements recorded at the United States Geological Survey (USGS) gaging
station near Maybell, Colorado, were used during Winter 1 to provide a record
of flow conditions.
Habitat Measurements Winter 2
During Winter 2, habitat mats were made at fish locations where
fish spent 15 minutes or more. Velocity was measured at 0.6 depth only. In
and out measurements were not taken unless extreme variation was suspected in
a habitat.
Th obtain accurate discharge data, a cross section station was

established at RU 81.1 near Maybell, and flow determinations were made on '
each biweekly trip. Fence posts wpxe driven into each bank to mark the
location. Holes were drilled through the ice 5 feet apart near the same
location each trip for water depth, ice thickness, and velocity moments. '
Velocity was measured using a Marsh McBirney model 201 Current meter.
cross sections were also established through embayment and backwater
habitats at III 81.1 and 95.7. Measurements of water depth and ice thickness
were taken from the same locations biweekly to determine how these habitats
changed throughout the winter under various flow and tagmratrure conditions.
In addition, all cross section measurements were referenced to known bencrmiark

elevations at each site by means of survey level to record elevation changes '
of the ice surface, water surface, and river bed throat the winter.
A series of dissolved oxygen measurements was taken during mid-winter to
determine if oxygen depletions were occurring as a result of heavy SHOW '
covering the ice for an extended period. Measurements were taken by lowering
12 '