Further to Johns comments the flood of 1980 at the Ganny and other eastern flows ie Wilmot cleaned out the spawning beds of silt, providing many years of quality spawning for steelhead and excellent survival rates as well, as the populations increased thru the 1980s until 1989 where record numbers were recorded in all eastern tribs, thru normal springs with normal runoff siltation occurs naturally once again, covering prime spawning gravel and reducing natural spawning habitat, hense the decline in steelhead populations, the flood in Peterborough where I live in 2004 had it happened 20 miles south along the lakeshore would have once again set the tables for another 10 or so years of increased steelhead populations, thats my 2 cents maybe a little more