7065

• UCREFRP Catalog Number: 7065
• Author: Behnke, R. J. and D. E. Benson.
• Title: Endangered and Threatened Fishes of the Upper Colorado River Basin.
• USFW Year: 1983.
• USFW - Doc Type: Bulletin 503A,
• Copyright Material: NO

Colorado River Squawfish
PtychocheiZus Lucius
Status
Endangered on federal and Colorado lists.
Distinguishing Features
This is the largest species of the minnow family
native to North America. Specimens 18 inches long or
longer are easily identified by their large mouth,
pike-like body shape, and olive-green back and sil-
very-white belly. Small specimens might be confused
with the roundtail chub by inexperienced persons.
Confusion is promoted because fishermen in Colorado
commonly, but incorrectly, use the name squawfish for
the roundtail chub. Among old-timers who once knew
the squawfish, the names "Colorado salmon," "white
salmon," or simply "salmon" were frequently used as
the common name for the squawfish. The upper jaw ex-
tends to or beyond the middle of the eye in the squaw-
fish, but only to a point in front of the eye in the
roundtail chub. Also, in young squawfish to a length
of 8 to 10 inches, a dark blotch occurs on the base of
the tail. This blotch is absent in the roundtail
chub. Appendix I illustrates the characters useful
for distinguishing the squawfish from the roundtail
chub.
Life History
The largest known specimens of squawfish seen in
recent years have been about 3 feet long and have
weighed about 15 pounds. It appears that the present
growth rate is much less than it was under the origi-
nal, unmodified conditions in the Colorado River
basin and before non-native fishes became predominant
over the native species. The reduced growth rate in
squawfish may be due, in part, from a change in the
prey species they consume, which was a result of a
replacement of the larger, native prey species by
smaller, non-native fishes. The possible introduction
of non-native parasites, brought into the basin in
non-native fishes, might also contribute to reduced
growth rates. Unverified weights of 80 to 100 pounds
are given in the literature. Judging by statements
in the literature and from the size of squawfish bones
found in ancient Indian sites, the length the largest
squawfish once attained was about 5 to 6 feet. The
plotting of a length and weight curve based on squaw-
fish specimens between 1 and 10 pounds, and projection
of the curve to 5- and 6-foot lengths, indicates that
a squawfish 5 feet long would weigh nearly 80 pounds
and a 6-foot specimen about 130 pounds. There is
much room for error in such projected calculations,
but it can be surmised that the largest squawfish
once attained a weight of 60 to 80 pounds.
The squawfish is a predator; its food is mainly
other fishes. In its first year of life, young squaw-
fish feed on small invertebrate animals in quiet back-
water areas and side channels off the main river. As
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