The only spearing I've done was when I was really young, Northern Pike and Red Horse Suckers (think that's what they're called?) We usually just called them "Suckers"... Our spearing for Northern Pike, was very early in the spring, when enough ice had left the creek so you could see through in spots. After the ice was gone, the Suckers were running. Spearing a Northern was really rare for us. Suckers would (and I would assume the Northern's as well) run up the river, right at the bank, and because the river washed out the bank, they were usually slightly under the bank. We were usually reaching out, away from us, and spearing under our feet, under the bank.
The point to that whole lead up... When you are trolling or casting for Northern, you want your lure, to be right above them, because their eyes are above, and see up, much better than down. When you are spearing them through the ice, you are directly above them. Are you fast enough with the spear, that before they see movement it's too late? Are you trying to spear from slightly behind, so they don't see it coming? Or is all of this just plain nonsense, and it doesn't matter at all... see a fish, and hammer down with the spear?