Post opener fishing has little impact on Steelhead populations IMO. Its a rather short, concentrated effort and as said, 90% of the fisb have already spawned. The single largest factor for successful reproduction is weather. A cool, wet summer that allows high hatch and survival rates does wonders.
Last year was a wetter and cooler summer than usual, particularly the first half. You'll see the result of that this coming fall with increased numbers of 'shaker' steelies returning to the tribs after their first summer in the lake.
Josh