Will a bitter winter affect fishing next summer?

This winter has been one of the coldest in decades

The short answer is no, at least not for us on Red Lake and mostly not for any lake, but there can be some effects for small lakes.
No matter what is taking place above the ice such as the -40 to -50 C temps and frightening windchills that  we've had this winter, beneath the ice the world is unchanged. Right beneath the ice the temperature is just above freezing and as you go deeper it gets warmer to about 39-40 F.
The ice will probably be thicker than normal, perhaps 45 inches by late winter. However, normal ice thickness here is 36-40 inches; so, it isn't all that much different. On big lakes like Red Lake which is 30 miles long, up to 140 feet deep and five miles wide in places, a little additional ice on top is meaningless.
You might think that the thicker the ice the longer it will take to melt in the spring. Our experience is the ice thickness has almost nothing to do with the time of ice-out. The type of ice can be a bit of a factor. If it is white and slushy, as it actually is this winter, than it is slower to melt than dark or "blue" ice. The thing that trumps all others when it comes to ice-out is spring weather. If it turns mild from mid-March to May 1, the ice will probably go out right on schedule - May 8, more or less, for Red Lake. If it is cold and cloudy, ice-out will be delayed. That is also the case when there has been a warm winter and the ice is thinner than normal.
So where does an exceptionally cold winter affect the fish? It can happen in smaller, shallower lakes. Big lakes like Red Lake are full of oxygen left over from open water in the fall and, of course, fish need oxygen to exist. Shallow lakes; however, have a more-limited volume. In these you can have "winterkill" where fish die from oxygen starvation. In these places you can sometimes see fish with their snouts poked right into the air at pressure cracks or pressure "blowholes" in the ice. I have even heard where the fish had flopped right out on top of the ice in their frenzy to get "a breath."
Mostly there aren't fish in these places to begin with, just minnows, which require less oxygen. However, I have seen where even all the minnows died from winterkill during a really severe winter.
A related bit of information about the cold's effect on fish occurs around our winter Nolalu home which is in the Thunder Bay area. Here almost all the little streams and lakes have brook trout, also called speckled trout. The very existence of the trout in the streams hinges on the number of beaver dams and therefore pools of water that they create. Usually, the pools don't freeze to the bottom while the streams frequently do. So if you're a stream trout fisherman, thank a beaver! This year, I'm afraid, everything will have frozen all the way. The trout will need to re-establish themselves from whatever lakes the streams started from or feed into.
There is a great website with information about fish and water bodies in the winter. It is the Wisconsin DNR's Wisconsin Natural Resources Magazine. 
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