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

that it differs with habitat type to reflect a resting mode in slow runs and
slackwaters and a feeding mode in eddies and backwaters. We attribute the
relatively greater movement during year 2 to lower flow regimes that may have
created more marginal conditions in fish habitat.
Figure 3 illustrates the local movement of 2 of the 10 radiotagged fish
monitored in year 1. Colorado squawfish OR-4021 occupied four favorite spots
within the same slackwater during a 24-hour period. The fish moved a total of
50 m during this time, but ended up only 10 m from its original location. This
fish occupied the four spots five times for periods of 2, 1, 4, 8 and 9 hours.
A second Colorado squawfish, GR-6106, in the same vicinity, visited eight
favorite spots for periods of 1 to 9 hours, all within a 50-m diameter area in
the same slackwater habitat. Gross movement by this fish was 118 m while net
movement was 10 m.
We conclude from these observations that local movement rates of 15 to 23
are normal for overwintering adult Colorado squawfish in the absence of
fluctuating flows. This movement is not continuous, but occurs between
favorite spots or microhabitats in which the fish is sedentary for several
hours before moving to another spot.
Local movement was also analyzed under stable ice and nonfluctuating flows
in year 2 to determine if ice cover affects this aspect of fish behavior. The
average local movement by 5 Colorado squawfish under stable ice conditions was
29.16 m/h. This figure did not differ significantly from average movement. of
23.03 m/h under ice-free nonfluctuating flows. Although their movement is not
significantly greater under ice, we believe Colorado squawfish use ice as a
cover element.
Local movement by an adult Colorado squawfish under stable ice is
illustrated in Figure 4. Fish GR-3422 occupied three favorite spots during a 2
hour period; gross movement was 30 m and net movement was 7 m. We conclude
from these observations that local movement by adult Colorado squawfish under
stable ice is not significantly greater than in ice-free conditions. We noted
that all fish monitored in areas characterized by a mosaic of solid surface ice
and jam ice remained beneath the former more stable form.
Razorback Sucker
Long-range movement by overwintering adult razorback suckers was not
considered extensive. In the first winter of the investigation, maximum net
movement by a fish was 10.5 miles downstream (Figure 5). Although one other
fish moved 4.4 miles downstream, 6 of the 8 radiotagged fish were found less
than 1 mile from their initial tracking locations. The average net movement of
these 8 fish during year 1 was 2.1 miles. In the second winter, maximum net
movement by a fish was 7.3 miles upstream, while two other fish moved 5.9 and
3.2 miles downstream. Six of the 9 radiotagged fish in year 2 remained within
3 miles of their initial tracking locations. The average net movement of these
9 fish was 2.9 miles.
As with adult Colorado squawfish, total movement by adult razorback
suckers was not very different from their net movement. In year 1, maximum
total movement by a razorback sucker was 10.5 miles, and average total movement
by the 8 fish was 2.3 miles. In year 2, maximum total movement was 10.4 miles,
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