9312

• UCREFRP Catalog Number: 9312
• Author: Persons, W., R. V. Bulkley and W. R. Noonan.
• Title: Movements of Colorado Squawfish in the Colorado River Inlet of Lake Powell.
• USFW Year: 1981.
• USFW - Doc Type: Report No. 8,
• Copyright Material: YES

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INTRODUCTION
During investigations of striped bass spawning movements in the
spring of 1980, 45 adult-sized Colorado squawfish were captured by
gillnets in the Colorado River/Lake Powell mixing zone (Persons and
Bulkley, 1980, Appendix A). This relatively large number of adult-sized
squawfish raised important questions as to the reason for the uncommon
density of these endangered fishes. Were they concentrated for spawning
purposes? Had they moved upriver from the reservoir? Or, were they
year-round residents of this section of the river-reservoir mixing zone?
The objective of this study was to monitor the movements of selected
specimens from fish captured in 1981.
METHODS
Collection of Fish
Fish were collected during the period May 24 to July 22, 19819 with
31 meters long x 3 meters deep, 6.4-cm square mesh multifilament nylon
gillnets at the head of Lake Powell near Gypsum Canyon (river miles
194-200) (Figure 1). One end of the net was attached by rope to the
shore and the net was fished in water from 1 to 15 meters deep. Nets
were checked every 0.5 to 3 hours during the day; overnight sets were
occasionally used.
A 1.3-cm square mesh fyke net with 15.25-meters lead was fished from
June 13 to July 12, 1981. The net was set with the lead perpendicular to
shore in shallow (0-1.5 meters) water and checked approximately every 12
hours.
Tracking Equipment
Radio transmitters manufactured by AVM Corporation for insertion
into the body cavity were used in this study. Transmitters were 3 cm x
1.25 cm x 0.6 cm and weighed 4.5 grams. Frequencies ranged from 40.370
to 40.430 MHz. Receiving equipment manufactured by Smith-Root, Inc. in-
cluded RF-40 tracking receivers, SR-40 search receivers, omnidirectional
and directional antennae. Radio transmission range was approximately 100
meters with the transmitter less than 1 meter deep. Inflowing Colorado
River water was extremely conductive and caused limited transmission
range.
Interference, or spurious signals, were occasionally received with
the SR-40 search receiver near Hite at river mile 169. Microwave trans-
mission from Hite may have been responsible for these signals. They were
not confused with actual radio transmitter signals because spurious
signals were not received with the tracking receiver (RF-40) which could
be tuned to a specific frequency.
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