Salmon and steelhead type question??

[heyfredyourhat]

Sorry if this is the wrong forum, but I didn't know where to ask. So my coworkers think because I am into the reefer thing that I know everything there is to know about the ocean and fish and da da dada.... Today one of them asked me "why is it that steelhead can live in the ocean and feast and then return to freshwater and not die?? And the same thing with salmon??".

Well I was unaware that steelhead do find there way to the ocean, but whatever.

Why is this???? I told him I would ask you guys...Thanks in advance