Channel catfish can over winter without substantial heat. (Well, big ones will just fine, little tiny babies tend to starve to death if the water is too cold for them to eat.) Catfish won't grow much when the water is below 55 degrees but they will survive. Mine are starting to eat well again now that the water is above 55 F.
Channel catfish survive wild in most of the USA. So if your fingerling stock is from a local hatchery, the catfish should be able to survive in local waterways over winter (provided they are larger than small fingerlings when the cold weather arrives.) Half of my way too small fingerings survived water at 32 F for a few weeks even but many were starving to death at that temp since they were too small to have the fat reserves to survive that long without eating. So, Provided your water keeps flowing and the catfish are not whispy little things, if they are local they should survive. When I talk about local, I mean if you live in a cold Northern state, you probably don't want to get catfish from a hatchery in Florida as they will be Southern stock and better adapted to warm water and not as good for your winters and the reverse is true, I would not want game fish from a Northern hatchery as they would not likely be prepared for 90+ F water that I could get here in the hot months.
Anyway, I know catfish can survive in places where water ways freeze over in winter so I'm pretty sure they will survive in a flowing AP system over the winter.
Thanks for the link. I will try them. I'm pretty sure trout wouldn't make an overnight ship (some don't even make the drive home) but catfish should be a lot less oxygen sensitive. Have you had good survival rates on catfish shipping?