I've said it before, maybe even in this thread, but we have known (at least fisheries professionals) for multiple decades that fishing has made the salmon smaller. And, in a few cases, larger. This most obvious with Chinook where they get fished as immatures for years.

But, in the last decade or so a much more dangerous factor has arisen. The salmon are now smaller at age; the quality of food is insufficient. In fact, some of the larger adults die when migrating back to the more southern streams where they swim into warmer water which raises their metabolic rate to the point that a full stomach of low quality food won't sustain them and they die.

Which means, if we don't fix the food chain, too, that even closing the marine mixed stock fisheries might not get the big fish back as they lack the nutrition to grow big rather than just lacking the opportunity.