Couple things about the age of springers. First, they usually migrate to the ocean at 1 1/2 years old, like steelhead and coho smolts and unlike fall chinook, which usually migrate the same year they are born, at 1/2 year old. So springers spend one year less feeding in the ocean. They also stop feeding and return early in the spring, so they miss their final adult season of summer feeding - and summer is when the days are long and the ocean is at it's most productive. So a 5 year old spring chinook only got to spend 3 summers in the ocean, and would be equivalent in size to a well fed 3 year old fall chinook or a puny 4 year old. 35 pounds is about as big as I've ever seen in person, is a damn nice springer, and likely is a 5 year old - the last one I saw that was in this class was 33 lbs, and was a 5 year old for sure as I did read the scale (used to do this for a living). So perhaps by some miracle that professional biologist might have been right, and you armchair bioligists who were bashing him just might have been wrong, as you seem to be confusing spring chinook life history with fall chinook life history. Just an observation