Have you walked the watershed area? Just wondering if there is any water of any type in your watershed that could have overflowed into the pond. I looked at the map but it is difficult to determine the elevation layout.
We were just talking here in the office, reflecting upon the time that we witnessed an osprey haul a largemouth bass off and drop it in another pond on the farm�
This type of unintended introduction of fish is very common. In fact, we see it all the time�
Mother nature will find a way to move life around.