RES do not do well in cold water -- RT need cool/cold water. There is a temp. overlap and it might work in the right place. Take a look at the temps of both. My guess is there are not many folks here that have those conditions which would support year round RT and RES. But if you are willing to restock RT in the fall many southern ponds will work.

RT - 10 � 24�C http://www.fishbase.org/Summary/SpeciesSummary.php?id=239

RES - NA But not native to upper midwest- http://www.fishbase.org/Summary/SpeciesSummary.php?id=3378