The issue of increasing by-catch of steelhead while targeting salmon returning to the man-made spawning channels is a very important component to this issue.
It is compounded by the relative survival of the species involved. There is little question that we are seeing a warming of the offshore ocean (the cause is for another topic) however that phenomenon is important. Typcially fish like chum, pinks, and sockeye doing better (above long term average) under those coniditions while steelhead do poorer. The result is that commerical fishery ends have more fishing time on the years of big salmon runs which typcially would occur when the steelhead runs are down. End result is that increased commerical happens when the steelhead population would be more affected by that by-catch.