Here's what I know, which aint much and others please feel free to correct this.
From my understanding, the fry stay in the bay and become part of the resident population. Once they grow to a size bigger than the resident population (on average 5-6 lbs) they then join the migratory walleye group. Also, in terms of the fry, the MNR have a yearly netting program to capture and count the fry which they refer to as "Young of the Year" (yoy).
Every year they use a net with a very fine mesh and basically trawl specific areas throughout the bay and count the yoy in each area that they have netted. The results indicate how successful or not the the spring spawning was. In some years they have found yoy in the east end of the bay and not the west end, others years the opposite and in some years yoy everywhere. In really bad years when the spawn was a bust they might not find any fry. Over the long term these results are graphed and you can see and understand the various population sizes of year classes. All of this information is available to the public at the following website.
http://www.glfc.org/lakecom/loc/mgmt_unit/
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Dan Elliot - A bad day on Quinte is better than a good day at work !!!
http://www.quintefishing.com