anemec: When I lived in Alaska I fished for Silvers in late August and early September primarily on the Kenai and the streams along the Parks Hwy and yes the Kasilof has Silvers. I can't remember when the run is the strongest. Here is a link I found that shows a fish calendar, scroll down toward the bottom.
Alaska Salmon Fishing
If Ard doesn't see this post you might want to PM him (Hardyreels) as he lives in Wasila and loves to fish Silvers.