I remember reading an article in Yankee Magazine about a man who called Snapping Turtles to the surface to capture them. The writer spent a week with him and watched as he called up multiple snappers from ponds people would swear didn’t have one. I truly believe if you live in the Eastern United States and have a pond older then two or three years you probably have a snapping turtle in it. I have raised them in tanks and while they are ok at fishing they don’t pose much threat to fish populations. An Alligator Snapper might be a concern in a small pond, since they are fishing specialists