Is it true that Jack Salmon cannot spawn? And if that is true, why do we have to release the un-clipped jacks?

Jack Chinook salmon are reproductively mature salmon that have spent one year in the ocean. While fisheries managers typically refer to adult salmon as the fish larger than 24 inches in length that spend 2 or more years in the ocean, in reallity jacks are mature adults and are an important part of the reproducing population of adult fish