One of the more annoying aspects of pike and pickerel fishing is seeing how many of these toothy critters end up with a hook around a gill-rake. I see a lot of this with smaller specimens, but it also happens with bigger fish - whether fly-fishing or gear fishing. A lot of it has to do with the way pike and pickerel feed - they inhale lures by forcing water through their gills. I see it a lot with flies and lures that are fished with a stop and go motion. You pause the lure and then the fish sucks it in. Bass often do the same thing.
A sure way to kill these fish is by trying to back the hook around the rake and bring it back through the mouth. The fish usually will thrash and you'll get cut or the gill tissue will get ripped - killing the fish. A great way to remove your lure or fly is to simply cut your line and back the hook through the gills. If you open up the fish's gills you'll see where the hook is. Just go through the gills with your hookout or pliers and carefully clamp around the bend of the hook and gently pull it through. It works great and next time you see that hook in those gill rakers you will know that by working fast and effectively, you will save the fish, your hands and valuable fishing time.