First a bit of geology: http://www.hotspotenergy.com/ground-...rature-map.jpg
even though surface water or ice temp may be far colder water near the bottom of a deeper lake will read about that of groundwater except when currents are present. Trouble is that O2 may be limited at depth so the fish are in a balancing act. Coupled with the fact that their metabolism decreases and therefore they require very little food during colder periods, the fishing sucks. Find a nice outflow area aka spring and you solve the O2 problem at times as well as a bit of the temps problem and you can catch fish more easily.
Techniques that work for me are suspended bead head, maribou flies under a strike indicator. Almost motionless but lots of micro action due to the feathers. Smallies, Trout, Crappie are all takers. They like smaller, very slow mouthfulls at this time of the season and this satisfies that.
South facing shorelines that catch the most sun can raise bottom temps to a few degrees above ambient water temps and are always an early target for me as well as dark bottoms over light colored ones as the dark absorbs more heat. Find a place where a nice white reflective boat house or dock stands over a dark bottom on a south shore and you've got the makings of a great spot.