Postbeetle,
Been there done that in my first winter of having a pond. Sad part is I still have so called experts in this field (not on this site) tell me there is nothing wrong with aerating in the middle of the pond in winter! Wrong!
I didn't really have dead fish right away but I had severely stressed fish come spring.
Take heart though. You may not have lost as many fish as you think. Many may have found refuge in another part of the pond.
