In the spring when they return to the river where they were born, they dont eat again prior to spawning in the autumn/winter. So they lose a vast amount of weight and the body changes shape dramatically. They are close to death by the time they spawn and nearly all die soon after.
I had to google this to find out what you were all talking about. I never knew about this process of change in salmon at spawning. Fascinating. You are never too old to learn something new. Thanks, guys, for the education.