7048

• UCREFRP Catalog Number: 7048
• Author: Desert Fishes Council ‎(Edwin Pister, e.
• Title: Proceedings of the Desert Fishes Council
• USFW Year: 1991.
• USFW - Doc Type: Volumes XX and XXI
• Copyright Material: NO

of fish contacted. Locations provided through aerial telemetry were generally
within 0.1 mile of the point subsequently located by ground crews. Generally,
aerial telemetry was conducted at ground speeds of 70-160 mph at above-ground
elevations of 50-1000 feet.
Radiotracking on the river was done primarily from jonboats, although ice
cover during January and February, 1988, prevented their use through most of
the study area. During this time, access was by vehicle along shoreline roads
and on cross-country skis over the frozen and snow-covered river channel.
Snowmobiles and quadratracks were found to be impractical because of the
unstable and rough nature of the river ice and the heavy shoreline vegetation.
Once a signal was received, the RF-40 receiver with loop antenna was used
to pinpoint the fish location. As soon as the signal source was located, the
boat was taken to the nearest shore or island, with care to not disturb the
fish. From land, the RF-40 receiver was used exclusively; first to identify
the fish by determining the transmitter frequency and pulse, and then to locate
the fish using triangulation. Triangulating the location of a fish involved
using the directional capabilities of the loop antenna to establish two or
three bearings at different places along the shore. Each bearing was marked
with two flagged metal rods driven into the ground 3 to 5 m apart and in line
with the sighting.
Each fish was determined to be alive by intentionally disturbing and
causing the fish to move at the end of the monitoring period, although some.
movement was recorded for nearly all fish during the monitoring period. If no
movement was detected or could be caused, a concerted effort was made to locate
the fish carcass or radiotransmitter. All fish were accounted for during this
investigation, except for razorback sucker OR-3230, which was not contacted
following release; transmitter failure is suspected.
Monitoring Fish Movement And Habitat Use
Monitoring
The fish and their associated habitats were monitored under three modes;
2-hour, 24-hour, and crepuscular. Only 2-hour and 24-hour monitoring were
conducted during year 1. In year 2, 2-hour and crepuscular monitoring were
conducted. The selection and order of fish to be observed for 24-hour and
crepuscular monitoring was determined within each of the three study regions
using a random numbers table.
Two-hour monitoring was performed on as many fish as possible during each
field trip of both years. Its primary purpose was to locate each fish, observe
it over a short daylight period, and record physical habitat measurements. Once
a fish was contacted, its location was monitored continuously for 2 hours.
During this time, movement and habitat utilized were recorded. A map of the
river reach occupied by the fish (about 250 m) was hand-drawn on the back of
each data sheet, to include habitats, prominent features of the channel, as
well as fish locations and movements. At the end of the 2-hour monitoring
period, habitat measurements were taken only at sites used by the fish
continuously for 15 minutes or longer. Each fish that had not moved during the
monitoring period was intentionally disturbed following habitat measurements to
insure that it was alive.
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