How cold is it apt to get up there, anyway? Upper-20s (Fahrenheit) in the morning, warming to 50 degrees or so during the day? One slight complication is that fishing is not the most aerobic activity, so pretty good insulation may come in handy even if it isn't all that chilly. In which case, you should look at the Patagonia Puff Jacket ($159; www.patagonia.com). It's a simple, hooded jacket lined with synthetic insulation similar to what they use in sleeping bags. It's very warm, water resistant, and breathable. The hood can also be removed. I should think it would be nearly ideal for sitting around a boat waiting for those walleye to strike.
A mid-weight fleece jacket may also work well. Not quite as warm as the Puff, but that may be a good thing when you're hiking around. You can spend a lot of money on a fleece piece, but I think L.L. Bean's Super 200 Trailwind Fleece Jacket ($69; www.llbean.com) is just fine. It uses high-quality Polartec Wind Pro fabric, a fleece that's naturally wind resistant by virtue of its dense weave. But it breathes nicely, too.
Either the Puff or Super 200 will slide nicely under some sort of waterproof jacket. If you don't plan on doing a lot of hiking, then I'd happily settle for something such as Helly Hansen's Impertech Parka ($70; www.hellyhansen.com). It's soft and well made, and WILL keep you dry if it starts to rain, no question. But it doesn't breathe for a darn, though that doesn't really matter when sitting in a boat. For something waterproof and breathable, look no further than Canada's very own Mountain Equipment Co-op's Tempest 2 Jacket ($198 Canadian; www.mec.ca). It's a nicely designed, basic piece of rainwear, using two-ply construction (meaning it has a mesh liner).
So there you go. Not a lot of money, but plenty protection. Have fun!