The cause of mortality is different from lifespan over populations. Assuming all other stress factors are similar over large populations from diverse locations then the remaining mortality possibility is natural death ( worn out muscles). Muscles in fish wear out slower in northern areas due to reduced use and slower metabolasms in winter.

Those stats have nothing to due with supp feeding and likely due not include data from private ponds ( or extremely limited).

The issues wrt feeding are a different from these.