That sounds doable. Pick a board that's thick enough to stay in the current, maybe 2 inches wide and 1 inch thick. Cut a notch on one side so a fish can’t get out, and add a small lip on the other side. Use a sturdy rope or braided twine to tie the board to a float that keeps it centered. When you drop it, the current will pull the fish in, and the lip will hold them until you come back. Just keep the boards dry and sealed so they don’t warp. I’ll bring the saw and the rope tomorrow.