Many factors affect the growth of catfish, such as climate, forage, and environment. A recent study taken from the Ohio River found the following catfish age averages:
Blue - 17.7 yrs to reach 35 inches
Flathead - 20.1 yrs to reach 35 inches
Channel - 20.0 yrs to reach 28 inches
35" catfish typically avg around 25 lbs.
This study found fish as old as 33 years!
The above info was documented in a 2017 report by the state of Kentucky. The study did not provide a weight of the examined fish. Exposing Paylakes used other data to make the statement - "35 inch catfish typically avg around 25 lbs."