How deep is the water you are over? Is this a pond? What I'm getting at is if you are over fairly shallow water the fish may move away from the boat and the zone of the cone. I have also see where the fish were up high in the water column and moved away from the boat. That's why some of us use planer boards on larger bodies of water for trolling expecially when the water is gin clear.

If pigs could fly bacon would be harder to come by and there would be a lot of damaged trees.