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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20

survive was 3-6% of the total dry weight of the fish. All
dying fish had lipid levels of 3-6% of the total dry weight
of the fish, significantly less than that of fish removed
while still alive (Table 6). Length was positively but
weakly correlated with time to starvation for all dying fish
(Figure 2).
All pellet-fed Colorado squawfish had higher lipid
levels than wild fish of similar size. Prior to the winter
period, the lipid levels of the hatchery-reared fish used in
my study averaged 28.9% lipid by dry weight (Appendix F).
These fish ranged in size from 26 to 59 mm TL (n = 180).
wild age-O Colorado squawfish collected from the Colorado
River between river kilometers 102.9 and 159.5 in early
October 1988 had a mean lipid content of only 14.9% for a
similar range of lengths (30-58 mm TL, n = 30, Appendix G) .
The mean lipid content of age-O cohort individuals collected
in mid-March 1989 from the same stretch of the Colorado
River was 13.6% (36-54 mm TL, n = 30, Appendix G).
For both small (mean TL = 30 mm) and medium (mean TL =
33 mm) fish, feeding determined whether a fish survived the
210-day winter period (Figure 3). At day 210, only 2 of the
original 61 starved, small fish were still alive (although
14 were removed on day 70 for lipid analysis). In contrast,
only 5 of the original 103 small pellet-fed fish had died
after 210 days (28 were removed on day 70 and 18 on day 140
for lipid analysis). The small fish that were fed brine
shrimp had 33 survivors on day 210 from the original 40 fish