7333

• UCREFRP Catalog Number: 7333
• Author: Valdez, R. A. and W. J. Masslich.
• Title: Winter Habitat Study of Endangered Fish - Green River, Wintertime Movement and Habitat of Adult Colorado Squawfish and Razorback Suckers.
• USFW Year: 1989.
• USFW - Doc Type: Report No. 136-2 for Bureau of Reclamation,
• Copyright Material: NO

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SUMMARY OF FINDINGS

ADULT COLORADO SQUAWFISH AND RAZORBACK SUCKERS IN THE GREEN RIVER
OVERWINTER IN SPECIFIC REGIONS, GENERALLY LESS THAN THREE MILES LONG.

Maximum net movement by an adult
r;:ldiotagged Colorado squawfish during the first
4-month winter period (December 1, 1986
through March 31, 1987) was 22.2 miles
upstream. Seven of the ten radiotagged fish
remained within a 3-mile reach of river.
Maximum net movement during the second 4-
month winter period (1987-88) . was 25.9 miles
downstream. Eight of the nine fish remained
within a 2-mile reach. We conclude from these
observations that the majority of overwintering
adult Colorado squawfish remain within a 2 to
3-mile reach of river.

Maximum net movement by an adult
radiotagged razorback sucker during the first
winter period was 10.5 miles downstream. Six
of the eight radiotagged fish remained within a
1 mile reach of river. Maximum net movement
during the second winter period was 7.3 miles
upstream. Six of the nine fish remained within
a 3-mile reach. We conclude from these
observations that the majority of overwintering
adult razorback suckers remain within a 1 to 3-
mile reach of river.

OVERWINTERING ADULT COLORADO SQUAWFISH AND RAZORBACK SUCKERS
EXHIBIT LOCAL DIEL MOVEMENT, USUALLY WITHIN AN AREA OF 50 M DIAMETER.

Average local movement by four Colorado
squawfish in ice-free water in year 1 was 15.23
m/h. In year 2, nine fish in ice-free water
moved 23.03 mlh and fIVe fish under stable ice
moved 29.16 m/h. This movement was usually
between two to fIVe favorite spots within the
same habitat. The fish sometimes occupied
these spots for hours. Thus, the majority of
overwintering adult Colorado squawfish move
15 to 23 mlh within an occupied habitat in ice-
free water, and about 29 mlh under stable ice.

Average local movement by 3 razorback
suckers in ice-free water in year 1 was 24.54
m/h. while 8 fish in year 2 moved 30.93 m/h.
This movement was usually between two to
eight favorite spots within the same habitat.
The fish sometimes occupied these spots for
hours. The majority of overwintering adult
razorback suckers move 25 to 31 mlh within an
occupied habitat.

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