7785

• UCREFRP Catalog Number: 7785
• Author: Thompson, J. M.
• Title: The Role of Size, Condition, and Lipid Content in the Overwinter Survival of Age-0 Colorado Squawfish.
• USFW Year: 1989.
• USFW - Doc Type: Colorado State University,
• Copyright Material: NO

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30

University on age-O Colorado squawfish collected from the
Green River by U.S. Fish and wildlife personnel showed that
of 18 fish collected during November 1987, 15 (83%) had food
items in their stomachs. One fish was collected in
December, and stomach analysis indicated that it had been
feeding. Observation of active feeding under simulated
winter conditions in the laboratory, combined with the
finding of food in stomachs of wild fish after the onset of
winter water temperatures in the Green River, support the
hypothesis that Colorado squawfish feed overwinter.
The results of my laboratory study may be useful in
developing models that predict overwinter survival of wild
age-O Colorado squawfish in nature. Perhaps the best method
of describing how my laboratory data might be useful to such
model development is to use a graphical approach. The
relation between fish size and time to starvation can be
represented by several curves (Figure 5). Line A depicts
the direct relation between fish size and time to death by
starvation, as determined in my laboratory study. Line B
shows that when fed, fish of all sizes survive simulated
winter conditions. The positions of line C and curve D
were estimated from my laboratory results. Metabolic
requirements of wild age-O Colorado squawfish are
undoubtedly higher than for my aquarium-held fish.
Therefore, if no food were available to wild fish or if wild
fish simply did not feed, then the fish size versus time to
starvation relation would shift upward, as represented by