I am doubtful myself, but I am at a loss for how this fish got into the pond.
Forgive me if I missed it but is this a new pond, drained and dried, drained and standing water, or what?
We've all seen herons spear something they can't swallow but I've never seen them move ir very far. But I have seen others animals move dead fish a good distance including dogs and cats after the heron spears them.