Those mini-jacks that cohoangler is referring to are 1+ that are from yearling releases, so that would be consistent with the zero age dying the next year. There are a couple of hatcheries in Puget Sound that can accidentally produce a large number of 0+ jacks (micro-jacks), but in my experience all of them died after spawning.

Do you have a link to the paper about maturing 0+ Chinook in the wild. I am surprised that a natural population could attain the growth rate necessary to bring on maturity as a 0+ in the wild.