What kind of structure do you have in your pond?
My Channel Cats are reproducing in my pond probably because I dumped several dump truck loads of pipe chunks into the pond in various places, i put it in there for structure and cover purposes but obviously some have landed probably with mud in one end that is giving them nesting cavities.
In your case Im not sure that they would have spawned at that young age, especially if the young are already up to 6", some of the educated guys may chime in and give a theory on that.
What I would guess they may be mud cats that have found their way into your pond, other than that, the difference in growth rates of the fish I stocked in my pond really surprised me. some of the same CC that I stocked, some seemed to grow literally twice as fast as others.
