this is simple, birds( mainly cranes)get fish eggs stuck to their feed and legs while wading and bring the eggs to your pond where they fall off into your waterand hatch, this is simple and i've known this for years. they can and do also fly over with fish in their mouth from another source and accidentally drop them into your pond from time to time. This is mother natures natural stocking method, how do you think all of the bodies of water throughout the world got stocked? lol this is meant to be a little funny but still true!!!
