So, what do carp do in the Winter? These scientist in Berlin, Germany had some fun by placing 37 tagged and traceable carp in a very cold (7°C, 44.6°F) natural lake during the winter to see what these fish would do. You will really enjoy this short YouTube. 
 
"The carp showed high swimming activity with no signs of hibernation. During the night, the fish stayed isolated or in small groups near the shore at a depth of about four meters. "The fish switched to open water during the day, where they actively swam at a depth of up to eight meters (at the bottom of the lake). Why the typically warm-loving carp remained so active in the cold water -  with a reduced metabolism - still remains a mystery to the scientists."
 
https://www.igb-berlin.de/en/news/what-are-carp-doing-winter