There is a world of difference between geologic time events and how long it takes green sunfish to find their way into a newly created farm pond. I can see fish eggs being transported by adherence to birds as a long shot that could occur over millions, or even thousands of years, just as life formed from primordial ooze and evolved through unlikely recombinations of molecules billions of times. However, when you build a pond one summer and find GSF in it the next summer inexplicably, it seems to me that upstream migration best explains the presence of GSF. The observation of self stocking of ponds is not a rare event.
