Anyone else notice that every picture I have seen of A. serracanthus appears to have damaged fins. Even those taken in the wild. Could I put forward the theory that fins on this species naturally degenerate for some reason and that is possibly accelerated in captivity?
That's because the fins on your fish are badly damaged. I'm almost sure it's Ameiurus serracanthus.
Yup, at some point in the past your fish has suffered severe damage to the finnage, but that's what it is. Obviously a survivor, deserving of another 7 years TLC.