Lou Heron, It is my theory that if you stock some type of fish; they will eat any or most arriving fry. So stocking fish prevents the intrusion of unwanted species. How the fry arrive? The turtle idea is a good one. I know that there are instances in which fish arrive and it is not due to flooding from another pond. I have a pond that is a half mile from any others, and its drainage area contains on other bodies of water, yet it has bass, brim and green sunfish. Maybe mudcat too, I don't know. But I do see instances where stocked ponds have only what was stocked. So I conclude that the stocked fish prevent other unwanted species from establishing themselves.
