I don't think there is an exact science to the # of water fowl per acre based on many variables. I have close to 100 ducks and geese on my 19-20 ac. lake. It is a self contained body of water with little watershed , just an abundant amount of groundwater below a certain level. On avg. you could have 4-5 ducks per acre depending on your nitrogen levels already, etc as stated by Jim. If using geese these #'s should be halved. Trial and error with close observation is required. In my case I'm close to the max., but they help control the weeds, add some free fertilizer to the clear water and we enjoy their beauty on the water while managing a LMB/SMB/BG and YP fishery. I hope this helps.
Rowly
