Water drawdowns of 1 1/2 to 2 feet were effected at Fort Randall Reservoir immediately following periods of major carp spawning in 1955, 1956, and 1957. Eggs thus exposed were killed. Predictions of the time of spawning were based on gonadal conditions of mature fish, water temperature and weather forecasts. Major spawning occurred in shallow (less than 1 foot deep) flats during periods of warm, calm weather when open-water temperature first reached 62-68° F. Effectiveness of the drawdowns in limiting carp reproduction was judged by the size of the age class produced each year in comparison to a previous year and to other species sampled by the same methods of spot-poisoning, shoreline seining, gill netting and frame netting. Size of the age class of carp established each year was relatively small. It is concluded that the planned drawdowns were primarily responsible for poor reproduction.
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