9314 ‎(2)‎

• UCREFRP Catalog Number: 9314
• Author: Wick, E. J. and J. A. Hawkins.
• Title: Colorado Squawfish Winter Habitat Study.
• USFW Year: 1989.
• USFW - Doc Type: Fort Collins.
• Copyright Material: NO

they did not need to leave it often. Fish remained within this backwater
during the entire winter and left it only a few times for only brief periods.
Most embayment use was at RMI 81.1. This embayment remained relatively
unchanged after ice-off and spring runoff. In addition to this embayment, one
at R G 71.6 was used in Winter 2 and another at Goverrnnent Bridge (R G 98.8)
was used early in both years. Fish used embayments throughout the winter, but
they would occasionally leave to use run and other associated main-channel
habitat.
All pool habitat use was within a mile section at the Lily Park study
site, a river segment characterized by eddy and pool habitat. This area has
no backwater and very little embayment habitat available during law flaw,
winter conditions. All three fish (C87, C89, and C00) in this area used pool
and occasionally run and/or eddy habitat during the winter.
In areas where a variety of habitats was available, fish appeared to
select certain habitat types over others. There was pool habitat within 0.3
mile of both the backwater (RMI 95.7) and the embayments (RMI 98.8, 81.1 and
76.2,) but no fish were observed to use these during the winter.
Fish using main-channel habitats changed habitat more frequently than
fish using off-channel habitats. Main-channel habitats may not provide as
many of a fish's winter needs. Advantages to the use of off-channel
(backwater and embayment) habitats may include:
1) low or zero velocity for energy conservation,
2) increased concentration of food,
3) easier identification of hoarse range area through
consistent visual or olfactory cues, and
4) protection from moving frazil ice
Off-channel habitats may also provide other indirect benefits, e.g.,
increased oxygen and primary productivity. The lower flaws present during
Winter 2 either made these off-channel habitats less suitable or made main-
channel habitats more acceptable.
Squawfish evolved within a system that provided variability of flaws
between years. Natural yearly variability would be important to avoid food
supply depletion during low-flow periods that would tend to concentrate prey
within the main channel where less cover may be available. If law flaws
continued over several years, populations of prey species could be reduced
since they would be subject to increased predation by the squawfish and
introduced northern pike and have fewer highly productive feeding areas
available during the winter.
Predominant habitat used in the fall, 1987, was pool; followed by run,
shoreline, and eddy. Backwater and embayment habitats were used the least in
contrast to high use of these habitats during the winter. Most pool use was
within the Lily Park study Area where this habitat dominates over other types.
Habitats used in the fall within the Maybell area were equally distributed
among almost all habitat types (Figure 9).
In the spring, eddy was the predominant habitat used followed by
backwater and shoreline (Figure 10). &bayments were not used during this
period probably since they tended to be flooded by the high flows. Run and
pool habitats were used very little. Backwater habitat was used in all three
study areas.
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