After you had dug up the ponds,it was then filled with rain water.During the rains,those ponds on the upper elevated (could be even slight elevation) ponds got filled in & excess of water started overflowing.As your ponds were got connected by this overflowing wae,ievarretits of fishes from those ponds came to your ponds,due to the temporary connection. After the rains this connection was not there,& this is how you got the fish in your new ponds.-B