No winter kills in at least the last 9 years. Really there are not alot of trees around and it does receive runoff from plowed fields. The sides are wrapped with rocks to reduce erosion. I will post some pics of the pond as well. Thus my thinking. The 7 foot finding was last fall I have now found out. We had a major drought last year, so I plan on taking a boat out this spring to get a more accurate number. Depending on the weather tomorrow, I may try to get down and catch some of the fish in question to snap some pics. The catfish have done very well in this pond for many years.