The goal is to take the big holdovers, which have proven to be adaptive, back to the hatchery to collect their DNA (more here). They then are returned to the river.
The program has been around about 20 years and has been successful. I’ve read that half of the browns at the Farmington are now wild. It helps that a big chunk of the river is C&R all the time. Imagine if this happened at the Swift!
Here are two videos that show what it is like catching and sorting browns. There are some incredibly pretty and large fish in the second video.