Timeing all depends on water temp. I usually start in on the spawning sholes when the temp hits 45+. Where I fish, the eyes usually spawn in late April, or early May, on borad, shallow gravle bays, as well as the face of the dam. They like the gravel bars near stram inlets too. There is one particular thin, flat point extending about 300 yards, with deep water on both sides, which is almost exclusively the domain of sauger spawning. I'd say that's my favorite early fishing area.
I usually fish pre-spawn when the males move in to the spawning grounds for fast action. When they are competing for good spawning sights, it seems to me that the eyes, and especially sauger are more agressive even than when they spawn. They go nuts for anything that looks like a minnow swimming through their spawning sholes. In the pre-spawn, the sexes are more or less segragated too, so you catch smaller fish, usually 1-3# where I fish, but avoid catching the females which are more dispursed in deeper water, so don't really threaten the spawning fish's success for the year. Besides, I find post spawn females to be far more agressive, and easier to catch, about two weeks after spawning ends. They seem to stop feeding agressively before the spawn, and more or less attack terrirtorially just before, and during the spawn.
Mid to late May, and Early june are far better fishing for the big fish for me. Pre spawn, through the spawning period probably accounts for 2/3 of the eyes I'll cach in a season. A 50-60 fish day, isn't uncommon, and at the peak of the pre spawn period, I can catch the sauger untill my arms feel like they'll fall off. The vast majority of them will be small male fish, though. A hell of a lot of fun, but the big ones come later. There'll be a couple of week slow period, then I find the deep rocky recovery areas, and beat the he!! out of the post spawn females. The last week in May, and early june accounts for about 2/3 of my fish over 5 pounds.