If you are just looking for fish to each the bug larvae, you could go with sunfish too.They're easy to catch, do a good job on any insects that fall in/on the water, and if you allow them to stay and breed for next year, you'll have free bait.The only issue is the legal transport/transplant of live fish. There might be a loophole in regards to "bait" status, but I'd check first.There's always the "goldfish" option. They are good for the bug eating task as well.In any case, you will have a number of options to consider.
Fatheads (Pimephales promelas) are extremely hardy in winter. In fact in Minnesota they are harvested from shallow ponds that regularly winter kill any other fish species that get into them hence why they are ideal for bait minnow production.
Are you saying that fatheads would survive being frozen solid for months?
If it's an ornamental garden pond why not add some type of flow like a waterfall? If there isn't power available for a pump they make floating solar fountains. Any surface disturbance will stop the skeeters from breeding.