There are still native fish in the Elwha but they are very few in number.
Checking on river flows this evening I clicked on Elwha and came across a press release dealing with this topic by the USGS. So if you want a little more info on silt behind the Elwha dams look up http://wa.water.usgs.gov/reports/news/news.wrir99-4215.html
The report is brief so be brave and indulge.