Almost 100% of gater problems are from people feeding them, either directly or from trash/litter. We have had several removed from the rv park when they got big enough for the state to come get them. That being said, I don't let my little dog to close to the water.
Little 4' gater along the trails at BBSP. No big one out that day, but there are over 300 6'+ and many over 10' gaters in 1000 acers of water and you see them all the time. I wouldn't let a dog of any size explore the waters edge. I'll get some pictures this summer.