3125

• UCREFRP Catalog Number: 3125
• Author: Wick, E. J., et al.
• Title: Colorado Squawfish and Humpback Chub Population and Habitat Monitoring.
• USFW Year: 1984.
• Copyright Material: NO

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Colorado squawfish of the Yampa River were backcalculated to find total lengths
of each annulus and relative growths of these values were computed (Tables 10
and 11). The mean relative growth for each annulus was calculated and given
(Table 12). Dissimilarities occurred during Age VII.+between Yampa and Colorado
River specimens of Colorado sauawfish. The Yampa River specimens had a larger
relative growth between its seventh and eigth year than the specimens from the
Colorado River (Table 13). Yampa River specimens experienced a growth increase
over the preceeding two years. Specimens ages IX+ and X+ also experienced an
increase in their relative growth during the eighth year, leading me to hypothesise
that possibly the growth increase is due to a switching of food types during the
eighth year or a charge to an environment more suitable to fast growth. Possibly
the extra Age VIII+ growth is due to Colorado squawfish preparing for spawning.
Because Colorado River specimens did not experience this growth increase during
their eighth year, the Yampa River growth might also be due to misinterpretations
of scales.
Colorado squawfish scales can be analyzed if sufficient scales a,
for proper analysis. Scales can be used to calculate age and estimate relative
growth and total length of the fish at various times. Colorado squawfish of
the Colorado River and the Yampa River showed similar growth characteristics.
Colorado River specimens grew more quickly at a younger age, but did not live
as long as tie Yampa River specimens. The Yampa River fish acheived greater
lengths than Colorado River specimens. The Age VIII+ year class was dominant
for both rivers. High temperatures combined with low flows restricted Colorado
squawfish spawning success in the Yampa River.
No scales were removed by United States Fish and Wildlife personnel during
the zummer of 1983 because workers believed that Colorado squawfish scales could
not be interpreted. From results I feel that Colorado squawfish scales