This video discusses the life cycle of salmon. https://www.youtube.com/watch?v=EqmGSexPaE
Salmon spawn in the same streams where they were born. The female makes “reds” which are like rock nests where she lays her eggs. The male fertilizes them and then the female covers the eggs with rocks and guards them. The eggs hatch and sack fry emerge and survive off their yoke sack until they are old enough to feed on insects as fry and then fingerlings. They move downstream as they mature and prepare for the transition from fresh to salt water. They migrate out of the stream and into the ocean and grow substantially until it is time to spawn and then they return to their original stream and the cycle repeats itself. Due to the exhausting journey upstream, after spawning the salmon die.
It is amazing that an organism would have evolved in such a way that its desire to spawn where it was born is more important than continued survival. It must have been a necessary response to the former abundance and success of the species that they didn’t need to spawn and keep reproducing. Dying after spawning makes way for new generations. Now that they are endangered it seems that this strategy could make it difficult for them to bounce back quickly, assuming the habitat is restored for them.
These fish are a cornerstone or linchpin species and an indicator of overall health of their environment. If they are endangered it is an indication of much bigger problems for the other species that depend on the salmon and steelhead trout. This is one reason why it is important that they can recover.