There have been ongoing problems in the N Pacific. The heavy pink programs have been correlated with declines in just about everything south of the N Pac. Apparently the AK sockeye are further north and don't compete with the pinks. Temperatures are warming, resources are shifting. It's likely enough things so that one isn't the "major" cause so nobody has to change their "minor" impacts.

Also, there were big slides in the Fraser at Big Bar and in the Chilko. These may have messed up in river passage and water quality conditions.

I think that some of the stocks have had various disease and parasite issues that may impact spawning success. You get the spawners but only half the production. I miss the day to day Fraser management as is was, back then anyway, the most data rich management we had on the Pacific Coast. And they still threw curves at you.

But when you could look back to data from the late 1800s/early 1900s and beyond to inform your management options you could blame ignorance.