RE: Mississaugi River
I have fished this River system quite a bit, mostly in the lower sections, Tunnel Lake and the River. I've heard the Rocky Island walleye population is very good, but it is a huge body of water. Contact the MNR (1-800-667-1940) and ask for the Sault Ste. Marie office.
Also, if I were to pick my favourite month to fish this reservoir system it would be August, walleye are deep (30 - 40ft), typically in mid reservoir areas on structure associated with the main river channel, but concentrated(easy to locate on electronics). Current areas are better than back water bays for me at this time of year. Spinner rigs work very well. This is stained water, I use orange or chartruese blades on 2oz bottom walkers with worms or leeches.