Effect of restrictive hunting regulations on canvasbacks and redhead harvest rates and survival
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.
Journal of Wildlife Management↗