What about the good old classics, like an M-80 tied to a rock? Can you get good fireworks (legal or otherwise) where you live? I live in NY, so all we are allowed are LED flashlights and sparklers.
When I did get my hands on those as a kid, 2-3 on a rock and a shared fuse, and anything nearby would float up for easy pickings. Drop them by the corn bag. It only stunned the fish, so most would wake up and swim off later.
I heard stories of when engineers were blasting the shipping channel in the St. Lawrence river in upstate, that simply massive fish would float up. Since they were not caught during angling, they were discounted from the record books. Even sharks would come up, which would regularly come up the river before the Robert Moses dam was built.
