In this case, I think it was probably from a high water event, as we have several last year. The hybrid bluegill were stocked this past weekend and the gambusia and green sunfish were there before. Also, I did check the catfish when stocked and there were only catfish looking fish on it!, granted I'm no expert and could have missed them. There are a couple of ponds above mine, across a road, it is possible that the road flooded enough for the fish to get into my pond. I guess I'll be adding a predator fish soon. Thinking off some HSB or maybe LMB...