Because of low population levels, there were especially restrictive hunting regulations between 1958-1965, including complete closures during the 1960-1963 seasons, for canvasback (Aythya valimeria) and redhead (A. americana) ducks. Banding data from 1952 through 1965 indicated that restrictive regulations reduced both harvest and annual mortality rates. During the period with very restrictive regulations, annual mortality-rate estimates ranged from 14 to 21 percent, much lower than before this period when estimates were 50 percent or higher.
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Effect of restrictive hunting regulations on canvasbacks and redhead harvest rates and survival