7145

• UCREFRP Catalog Number: 7145
• Author: Inslee, T. D.
• Title: Spawning of Razorback Suckers
• USFW Year: 1981.
• Copyright Material: NO

once again available to the population. This will require a combination of
higher spring flows and management of the Grand Valley floodplain. The
leasing or purchase of key riverfront areas in the Grand Valley where
dikes could be removed and the adjacent low-lying lands allowed to flood
should be explored. Natural draining of such areas after runoff would
prevent the establishment of resident populations of predacious fish.
Recommendations
Analyses of data collected in the Grand Valley (Osmundson and Kaeding
1989, and new data presented here) and in downstream reaches of the Colo-
rado River (McAda and Kaeding 1989) have revealed a strong relationship
between flows and the annual abundance of Colorado squaFfish young. The
high-flow years of 1983 and 1984 resulted in low catch rates of young
Colorado squawfish, as did the low-water years of 1988 and 1989. Peak
flows during 1983 and 1984 at the State line gage were 60,200 and 68,300
cfs, respectively; during 1988 and 1989, peak flows there were 15,000 and
9,480 cfs, respectively. Based on data currently available, we feel that
flow conditions of 1985 should be viewed as optimal for maximum production
of Colorado squawfish young, followed by those of 1986. It is not known
whether flows somewhat higher than those provided during these years, but
not as high as 1983 and 1984 levels, would result in even greater produc-
tion of young. It is also possible that physical as well as biotic changes
brought about by the high flows of 1983 and 1984 provided the necessary
conditions that were conducive to the relatively high reproductive success
realized in the succeeding two years. Flow conditions and production of
young should never fall below 1987 levels (State line peak of 22,000 cfs);
except during years of extreme drought, such flows should be viewed as the
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minimum acceptable.
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