I must be missin somethin, is there a warm water trout?

they are still there, just a lot less active because of their motablisms slowing way down to survive the colder water and conserve energy.

If you can find some underwater springs they might hang out there (same place they hang out in hot weather because of the constant supply of cold water). The spring water may be quite a few degrees warmer than the surrounding near freezing stream. Also in deeper holes.

Like people have said, they are still there. In the cold water months trout are very conservative with their energy and appetite. They will hole up in deeper holes with less current and they will change their appetite. They won't aggressively chase down food and they eat much smaller pieces of food. The game changes drastically during the winter.

They stay were they normally are.

Are talking about RIVER trout? or lake trout big water trout like the great lakes??

I have taken some very nice lakers from inland lakes her in MI thru the ice and usually it is from the deep holes using smelt or jigging swedish pimples

They might hop on a flight to Rio...or they JUST might stay put and hide under a rock. Your guess is as good as mine!

In streams they are deeper in slower water and way more sluggish. They usually will not move far at all for food so you need to present it right in their face.