If you want wild fish, quit fishing.
If you want lots of fish, turn the harvest/production of fish over to private interests as that is what they desire.
If you want a life long career producing paper ..... work for the government.
The critter itself may be complicated....and certainly it is over-thought to death....but producing them is simple.

Why not divide the rivers?

All wild/no fish kill

All harvest, plant the hell out of it.