My understanding is that much of Puget Sound is pretty flat/soft. What we think of as classic rockfish structure is not a large percentage of the sea floor.

The glacier(s) that covered the basin 15,000 years ago pushed a lot of material ahead and as they retreated, probably dropped a lot of rocks/boulders which are now probably buried under inches/feet of sediment. Run-off from the rivers and the subsequent increase in sediment due to logging, site construction, road work, etc has probably exacerbated the coverage of smaller "rock piles" which may have increased the population declines. Add in the damage done in the 70s and 80s when WDF opened up the Sound for the trawl fisheries and continuing problems with some trawl fisheries (shrimp), purse seines set in shallow water, gill nets that drag, many of the remaining small rock piles are probably also affected.

What techniques and "deposit material" do we use to replace what has been lost?