Wow!
This bears out the numerous anecdotal claims of good bass fishing in the J and lower Susky. The population structure of SMBs from age one to 15" is very strong.
A point worth remembering is that a 15" river SMB in PA is about 7-8 years old. In other words, the current strong population of big fish over 15 inches are from the year classes from about 2009 going back to about 2003 (for a 20" fish). This was during the height of the early years of the bass crash when there was great concern that younger fish would not survive (and many didn't). Nevertheless, we can conclude that fish that survived those years had good continued survival.
Another, I think this is less likely... possibility is that the current numbers of big fish may involve significant numbers of fish that have migrated down into the middle and lower Susky from the West and North Branch.
Another positive angle that leads to optimism is the fact that there are so many adult fish and large adult fish. Such an increase in numbers of adult fish should result in more spawning and this may start to improve YOY in coming years (let's hope).
I'm still concerened about the poor YOY, however, survival of adult fish is looking very good and the numbers of fish of the size range we like to catch is tremendous.