It's basic comman sense; manage the runs to take every single extra fish for harvest under optimal river and ocean condition assumptions, year after year on systems all ready far below historic carrying capacity. What happens? Within a few generations you hit critical mass. Look at the Hood Cannal as as example, pristine environmental conditions yet even with massive intervention from humans in the Hamma Hamma project the can't get the run to come back. look at the Queets, well below carrying capacity barely makes escapement yet pristine habitat.
Salmon and steelhead will spawn in a ditch if there is no more room in the river and be successful, oil and fuel runoff and all. 150 years of massive comercial harvest takes nature's safety net out of the equation. There was a reason for massive abundances, fertilizer was a big reason, I'm sure our forests are going to run out of nitrogen at some point due to being starved of it for the last handful of decades. Our rivers should be packed from bank to bank 9 months of the year with all species of salmonoids. The rivers and habitat are capable to produce that even today. A massive abundance of fish creats a massive abundance of bugs and then more fish.
I was correct about the Bundys as well not to mention Bigfoot and probably Gnomes....