I first bought Pond Boss circa 1992. There was a study about cormorant and raccoon depredation in four ponds.
1 Was left to nature.
2 Had some protection like noisemakers
3 Had more protection including "Mr. Scary", a solar PV panel charged a battery. When the battery was charged, Mr. Scary was powered up to blow up a doll that makes noises every 20 minutes or so.
4 Had total fencing.

1 Was eaten up.
2, 3 did better but even Mr. Scary failed after several months.
4 Worked.

I may have some details wrong.

I now live on a 40-acre lake with bass and bream west of Auburn, Alabama.

Every day on the green side of the grass since I had Cancer surgery is a gift from my Creator and is not to be wasted.