Today is the first ice free day we've had all winter. Ice was rarely thick and often had an area of open water but always had some. Today we found four dead Redear. About 4" long....looked generally ok (I'm no expert)...no deformaties. The pond is 1/4 acre...16' deep on the center. We stocked LMB, FHM, and Redear last spring. Our open-loop geothermal system empties into the pond (hence the no-ice corner). Have some algae growth already in that corner. Should I be concerned? Or is this just end of winter stress?

Uh-oh.

I wouldn't be concerned if you had an open corner...

I wouldn't worry about it unless you see a lot more after ice out. Some fish just don't make it thru the winter.

Four fish is nothing to worry about, four hundred fish would be. I wouldn't be concerned at all, chalk it up to winter stress.

I lost a three RES fingerlings and one 7-8" RES at ice out on my 1/4 acre pond as well.

It keeps happening. We find a dead Redear once or twice a week. I know Redear are called shell crackers and we don't have snails. Is it possible they just don't have enough to eat?

Try and catch a few and post pics. Some winter stress related death in RES in your area is to be expected. They eat a lot of stuff besides snails.