I've certainly had my share of trespassing, theft and vandalism issues at our property. IMHO nothing will eliminate trespassing especially if you are an absentee owner but also my experience has been you can reduce trespassing through the following courses of action:
1. Research the trespassing laws in your state/county. Know what the laws are and what your rights are as a land owner.
2. Get to know the local law enforcement. In my area there are two Deputies that patrol the area. We have met and talked with both of them. They are great guys. Let them know you on a personal level.
3. Make sure your entire property is fenced.
4. Patrol your fence line as often as possible, repair any broken or cut fencing.
5. Post "No Trepassing, No Hunting, No Fishing, No Motor Vehicle Activity" signs along the entire fence line and along every trail on the property. Surround your pond with the signs. At a very minimum post them at the interval required by law. We have gone way beyond this interval along the fence line. You can purchased quality aluminum no trespassing signs in bulk on Ebay (25 signs for about $45 with shipping).
(Ebay no trespassing signs). The signs are very visible and are reasonable enough to replace. IMHO the plastic ones are a waste of money, the don't hold up. With the bulk signs in the link you have to drill your own holes but that is easy. We mount them to the fence using heavy wire twisted tight with the ends cut off short. That makes them harder to steal. Along trails and around the pond we pound in "T" posts and mount the signs on them. When a sign goes missing goes missing we replace it immediately.
6. Buy reasonable game cameras and surround your pond and other valuables with them. Mount the cameras in security boxes and use a locking cable (Python cable) to secure them to trees. Put them high enough in the tree that they cannot be reached on foot. All of ours our mounted at least 10 feet up so covering them up or otherwise tampering with them is difficult. If you capture an image of a trespasser forward the image to your local law enforcement. They might know who the person is and be willing to contact them.
7. Use "property under surveillance" signs and post them in any location that you suspect people are entering your property and around your pond.
9. Get to know your neighbors. Meet them face to face. This will do two things, first you might recognize as trespasser when caught on camera (one of the trespassers on our property was a neighbor) and second you can make the neighbor aware of the trespassing issues you've had and ask them to keep an eye out for trespassers as well. Tell the neighbor that you have added security cameras and that you intend to prosecute trespassers and ask the neighbor to spread the word.
10. If you are an absentee owner try to arrange to have family, friends or neighbors, check on your property as often as they are willing to.
11. Determine the legality of shooting firearms on your property and set up a safe and legal shooting range. Practice with the firearms frequently on your property.
Basically you need to make your property as uninviting as possible to trespassers. We have had way more than our share of issues with trespassers and are utilizing all of the above methods. We haven't eliminated trespassing but we have reduced it significantly. The signs and cameras cost money and are a hassle but IMHO are good deterrents. Plus with the cameras you get the bonus of getting some good wildlife images.
