It sounds like the tiles are appropriate structure for the channels to reproduce but given the sizes, timeframe, local conditions, and lack of catching fingerlings I would lean toward the smaller ones being slow growers. I would go with Theo's suggestion and do a cross-sectional aging if you want to be sure. Kiser lake, not too far from you, is a 400 acre lake with lots of structure but reproduction is intermitten at best so the DNR restocks channels periodically.

I have many fond memories of nights of catfishing myself.



"The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge." Stephen W. Hawking