Don't know the particulars in SW Washington due to differences in run timing I think it is pretty clear that the summer and winter fish would be at different places in the ocean and different times of the year. This could lead to different survivals.

Here on north Puget Sound Rivers while the winter returns (both hatchery and wild) went into the crapper during the mid and late 1990s the summer fish held their own or even increased some areas. In the last two years the winter runs have gone up some (better survival) while the summer run returns have fallen to as much as 1/3 as their abundance a couple of years ago.

Bottom line there seems to be little correlation between summer and winter steelhead.

Yes the summer and winter steelhead smolts migrate to sea at the same time of the with peak migration typcial in early to mid-May.

Tight lines
S malma