I can't believe no one suggested a flat head catfish, I've kept several and they are very mean and can be trained to come when called! I also live where very big bowfin are caught, just looking at a big bowfin skull will make you think twice about going swimming where they live but a really big one would be difficult prize to catch keep or even grow. I made a net out of wire mesh hardware cloth and a bofin about 36" or bigger bit through it and ripped it apart. It was at night and I was in chest deep water trying to catch the thing! Very thought provoking to say the least!