WDG tried the "spawn only the big ones" with Skamania summers a long time ago. They used the 3-salts, so that the fishery would have larger fish. Since saltwater age has a strong genetic component, it worked. What they got back was 3-salts. Just not enough to sustain the population because the extra year of marine mortality made the run un-suatainable. Went back to spawning all they had.