http://kbbi.org/post/lower-cook-inlet-pinks-show-early-strong-run-isnt-certain

"Escapement goals were exceeded in several systems. Too many fish in a stream or river can actually damage future returns, and the Pinks returning this year are the fish that hatched in 2015."

First I've heard of this.

It is possible to have too many spawners. Probably when you exceed about 2.5 to 3 kg/sq metre of stream. Pinks have been known, especially in Alaska, to have so many fish in the stream that they remove all the oxygen and essentially kill the fish in the stream. Actually, same thing happened about 20 years in, I believe, the Similkameen. Lots of hatchery Chinook came back (below the densities listed above) but it was a hot, dry summer. Low flows, lots diverted, low oxygen. They not only killed themselves but most all the other fish in the river.

Now, a manger will tell you that one fish over the escapement goal is "over escapement" and 10 or 15 over is "catastrophic". The escapement goal for Puyallup watershed pinks was set at 19,000. That was supposed to be MSY. In the early years of this century the watershed hosted a million or more without grave problems.

That's interesting thank you. I can certainly see there spawning interfering with other species.
I hear you about oxygen levels. Not sure if that happened in this case. What if those 4 million they caught had spawned? The pink return would be dismal?

Obviously whoever wrote the article doesn't know pinks. They are essentially fixed 2-year fish so 16 had nothing to do with 17. A quick read had a really good run two years earlier. Stands to reason that the return 2 years later would be pretty good too.