I guess it depends a lot on the type of folks you have around. In most area's and towns I have been around, most everyone is good and God-fearing. These are the type of people who would ask to fish a pond even if there was no "posted" signs up, and are people I would always welcome if they asked. Most would not even ask to fish if the land were posted. It is a good idea to go over your "rules" with them to prevent abuse. Rules could include: ask each time, and/or if you bring friends along., only fish certain days, hours, months, etc., "catch and release only". Personally I abhor that practice and see it only as a "senseless maiming", and/or unnecessary education of my number 2 protein source (venison is #1). I think public water fish population regulation is best left to the state reg's, and one should always stop fishing when the desired, legal number and size of fish is caught. That way, you eat good, and no fish is unneccesarily harmed. I put "catch and release" fishing one step below golf, which at least harms no good food source. Certainly both are fun, but I am a lot happier using my free-time to "bring in the bacon". My favorite thing about golf is that it keeps some folks away from the boat-launches, and away from some of my favorite "fishin-holes".
Most ponds in my neighborhood are largemouth bass / bluegill combos, and rarely have just the right balance, meaning one of the two should be harvested at all times. Both are good eating. What species you want kept, possibly what age class, etc. should always be part of your "rules". The "rules" need to be kept up to date, and fishing for certain species ought to be banned when/if populations get a little low. The good folks should be called up whenever there is a rule change. By letting the "good folks" in, you can pick some good friends, who may be called upon when you need a hand. The more "good-guys" you get on your side, the easier it will be for you to keep out the "bad" ones when you are not around.
The net affect of them signs is to keep most of the "good" folks away, while they are interpreted as "good fishing" or "good hunting" by the bad ones who you really do want to keep away. Luckily, them bad ones tend to be a relatively unintelligent lot, and are easily "duped" by something like a big "skull and cross-bone" sign that says something like "WARNING, water is toxic due to heavy chemical pollution. Do not eat fish. Severe illness may result from touching contaminated fish and eating may be fatal. Maintain minimum downwind presence of 50 yards, and upwind of 10 yards unless wearing oxygen supplying breathing apparatus (OSBA). Breathing of airborne fumes may cause severe illness, inferttility, or death". The more official looking you make it the better. Use lots of "fine print" Most of them (not all) can read. All know the meaning of the big, red, skull and cross-bone. If you want to waste some cash on posted signs, do it, but I think you would be farther ahead shredding and using it for camp-fire kindling. One thing is for sure, they wont get you no friends. Who couldn't use a few more of them.
