7145

• UCREFRP Catalog Number: 7145
• Author: Inslee, T. D.
• Title: Spawning of Razorback Suckers
• USFW Year: 1981.
• Copyright Material: NO

at their yearly high. During winter, however, activity is much reduced due
to water temperatures near zero. Colorado squawfish and razorback suckers
are primarily in a maintenance mode during this time; though not entirely
dormant, their movements are localized and probably involve minimal feed-
ing activity and avoidance of moving ice (Wick and Hawkins 1989, Valdez
and Masslich 1989).
Review of Winter Habitat Use
During winter in the Grand Valley, adult Colorado squawfish primarily
occupy pools and slow runs; large backwaters are also used but are few in
number (Osmundson and Kaeding 1989). Habitats occupied at this time vary
in depth, but are generally deeper than habitats occupied at other times
of the year. Mean depth by month at the locations of radiotelemetered
squawfish during 1986-1989 was 5.1 ft for November, 5.0 ft for December,
4.7 ft for January, and 3.8 ft for February. Data also indicated that
squawfish were more likely to use shallow sites if there was ice cover.;
Most sites (> 50%) were of very low velocity (< 0.35 ft/sec); the mean-
column velocity of some sites was relatively high (1.0-1.95 ft/sec), but
we suspect that the fish may have been residing on the bottom where veloc-
ities would be much lower.
For razorback suckers, pools and eddies were primarily used throughout the
winter, though we did note an increased use of runs during February. Sites
used were generally deeper than those used by Colorado squawfish. Mean
depth of sites where radiotelemetered razorback suckers were located was
6.4 ft during November, 7.2 ft during December, 6.4 ft during January, and
6.8 ft during February.
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