7603

• UCREFRP Catalog Number: 7603
• Author: Nesler, T. P.
• Title: Endangered Fishes Investigations
• USFW Year: 1991.
• USFW - Doc Type: Federal Aid Project #SE-3 - Job Progress Report.
• Copyright Material: NO

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which the first and second backwaters encountered in each segment were sampled
with two seine hauls per backwater. Minimum depth of any sample could be 0.3
m, and area sampled had to comprise approximately 25% of the total area of the
backwater. Width and length of each seine haul was recorded, though in
practice the width was considered constant at 4 m. Within the seine sample
area, maximum depth was recorded, and also the depth halfway between each
shoreline and the maximum depth point. Other data recorded included river
kilometer location, backwater type (main- or side channel), backwater length,
backwater temperature, main channel temperature, and maximum depth of the
backwater.

All fish collected per seine haul were examined briefly in the field to
identify and enumerate common, nongame fish species and release these fish.
All gamefish were separated and kept for length measurements, scale and
stomach samples. Stomachs were removed from larger fish (>25 mm) and
preserved in diluted 10% formalin. Smaller fish were preserved whole. The
remainder of the fish sampled were preserved in formalin for identification or
screening at the CSU Larval Fish Lab to meet needs of the standardized
monitoring data base. Apart from the requirements of the standardized
sampling design, extra seine hauls would be made in a given backwater if the
presence of gamefish species warranted extra effort to increase the sample
size of gamefish. Also, additional backwaters located from RM 140-128 were
sampled in a similar manner to increase the sample size of gamefish. All
gamefish preserved whole for stomach content analyses were measured in the lab
for total length. Stomach contents of all gamefish collected in seine samples
were analyzed in the same manner as above.

Job 3: Northern pike habitat utilization.

With the presence of radio tagged northern pike in the Yampa River, sampling
trips included searching for these fish via radiotracking. Using an ATS
receiver and 2.5 m whip antenna to monitor the various frequencies employed, a
given river reach would be searched throughout for signals emitted by northern
pike suspected of being present within the reach. Upon detection of a
specific signal, continued approach toward the location would be made as
quietly as possible to avoid disturbing the fish. Using the ATS receiver with
a Smith Root directional antenna tuned to the 30-32 MHz frequency range, the
location of the signal would be pinpointed by triangulation from shore to
determine the habitat type occupied by the fish. Thereafter, the fish would
be monitored for 15-30 min to determine its level of activity. This would be
classified as stationary, active within a specific habitat, or progressive
movement upstream or downstream. During this time, the presence and location
of adjacent habitat types, cover, and aquatic vegetation would be noted. In
some instances several pike could be monitored in the same locality.
Movements of these fish in relation to each other would also be recorded when
possible. Searches for radio tagged northern pike were conducted from
approximately RM 180 (Milner, Colorado) above Hayden to the confluence with
the Green River, and downstream to Split Mountain north of Jensen, Utah.