There used to be huge kelp beds all over the inside strait. One theory I've heard is that when the sea otters were hunted pretty much all the way back up to alaska the red urchins lost their primary predator species. The urchin populations have been growing pretty much unchecked for decades, as local divers can atest to, and they feed on all the kelp roots taking out all the beds. No kelp beds equals no where for herring to spawn. No where for herring to spawn equals much smaller herring populations which equals much smaller salmon/groundfish stocks.
Sounds like a plausible theory to me.....