This is the same time I Will be in quetico aswell and I have always gone in early june so I am hoping the fishing conditions will be similar with this early spring. We always do well trolling shoreline. Some lakes/bays produce more then others and it usually has to do with water depth and clearity in my opinion. Troll baits that go different depths to figure out where fish are, and if you are near any moving water this time of year I would say jigging would be very productive for the walleye, depending on the water temps again.