They are on their way to become good engineers. Why this, why that, what about this.

I am sure there are many experts who know better but I'll give it a try since they may be busy fighting each other.

Bucks come earlier to establish the territory and they also stay longer to protect the eggs and the longer in the river the more they match the environment (by getting darker) for concealment.

Not all salmon die. About ten percent of Atlantic salmon survive the spawning and return to ocean. Some say Atlantic salmon is East coast steelhead?!