Gator,
Post the property. Either with signs or purple paint. Then when the guy shows up, call the sheriffs.
If you aren't there when it happens, he is still trespassing and the signs may run him off, but you will have more legal leverage if it is posted.
New idea, pardon the craziness of this, but it just occured to me. Drive a stake into your pond on each side, just under the water line and tie a piece of monofilament between them so that it is stretched 6 inches under the waters surface or so. Ideally, close to the good fishing structure.
If it is broken, you had trespassers. If they had a trolling motor, you might have wound your line up in it real well. If they had no boat, you hung a few lures for them. If they had a boat, you still made fishing difficult. They would have to cut the line to fish or not cast across it. Placement would be the key to reducing the fun of a good poaching trip.
