With that much water your would have to spend a lot of time fishing to even get a glimpse of the fish populations that exist. I know a quite few guys you could hire to do the job!
I am assuming that this lake is pretty much devoid of structure since it is a prairie basin lake (at least that's what I call them). If you have the time you may want to fish the warm side of the bays immediately after ice out. That will tell you if there are Northern Pike. After the water warms, you should still stick to the bays to see if you have Largemouth Bass, Crappie, Bluegill, Yellow Perch. They will be in the warmer shallow water in the spring. I am betting that you have all of the above since the lake has been there since the 1990s.
A man could make a lake that size his life's work!
