I just read an article from North American Journal of fisheries Management on Flathead Catfish movements and habitat in the Lower St. Joseph River which could and does apply to most of Indiana. They used electric transmitters so this information is accurate. Some of the information that I thought would be useful to us fisherman is that the flatheads stuck to wood debris 70% or better of the time and liked riprap also. When the water reaches 10 celsius or 50 degrees fahernheit they become pretty inactive and are in their wintering habitat which is deep over 4 meters. They did not move any distance when in Wintering habitats until the water reached 50 degrees and then over a two week period they moved back to their original location from the warmer months. It said they moved a distance of about 1000 to 2000 meters in Spring and Fall when returing to these locations. It said in the spring they liked locations of a depth of about 2-5 meters and even over 7 meters. In the summer they were in shallow water from about 1-3 meters and in the fall they liked water that was deeper than 4 meters. I found this very interesting, fish a little deeper in the spring than you would in the summer, in the fall fish for them deep. When the water hits 50 degrees the flats are moving to the spots where you usually catch them just holding at different depths. Stick to fishing wood debris or trees and riprap. If you hooked some big ones last year they will be back to their original spots this year. Good luck.