Thiamine is, and has always, been there in the bait.
However, when the Ice over is excessive there is little food for the bait (chubs I believe) they loose weight---not thiamine.
When bait looses fat and weight it takes more of them to satisfy the game fish so they get a much higher dose of thiamine over the Winter than is normal.
This causes them to die off and/or become much more prone to other negative issues.
Believe that this will affect most all of the game fish to some degree.
I too hope for the big return run and can only hope they did OK while eating bait fishes and growing
Sadly it may have been more than last years run lying on the bottom but some future runs as well.