Jim...alot of folks say water temps below 40* is not worth the trouble as fish go dormant. Not a proven theory as it's not really been tested. I've caught many when only the shoreline was thawed and the rest of the lake was still iced over.
Warm water discharges are a good place to hit too. The small ones will be very close to the outlet...bigger ones sometimes a considerable distance away from them.
Rivers are better than lakes in cold weather....currents etc keep the fish a bit more active.
Feeding periods also not as often or as long as metabolism is slowed down considerably.
Alcohol based flavorings vs syrups/sugars are best to use also as they don't "gel" in the colder temps. Some fish oils are good also...ie pure salmon oil...it doesn't gel/freeze like sardine oil for example. Put a jar of sardine oil in the fridge and it'll turn to "wax" and won't even pour. Salmon oil won't...it stays liquefied and disperses scent well in the cold.
Anywho...in short, it definately slows down....my goal this year is to catch one through a hole in the ice....if we ever get any
