I am very glad to hear that those depressions are likely from fish. The minnows I put in late last summer were only about 3" or so. I am surprised they survived let alone grow enough to spawn. However there is also always the possibility that someone dropped in some mature fish without letting me know.
Thanks for the comment dlowrance. We are very blessed to have the opportunity to witness and enjoy such sights. I just wish I had my real camera at that moment. It was such a beautiful morning all around.