Ever hear of Didymo or Rock Snot? This is an algae that is spreading accross the country in major trout waters. It has been reported in the South fork of the American River in California and I had the displeasure of seeing it in the SF of the Feather below Little Grass Valley Reservoir. It makes NZMS look like a light weight in terms of potential damage to a fishery. When I first saw it on the Feather, I thought there was a decomposing carcass of a deer on the bottom of this small pool.  The area was gray colored and a large number of wide ribbons of the algae were waving in the current, like tendrils of loose flesh.  But then I saw it everywhere completely carpeting the stream bed.  On the rocks it was about 2 inches thick and felt like  carpet. There was very little insect life under the rocks and very few fish in the stream, which used to be a great little fishery if you didn't mind some free style cliff climbing.

Because its an algae and its single cells are microscopic, its easily transported on anything that comes in contact with infested water. I treated my shoes and lightweight waders with dilute bleach to disinfect; other chemicals might be more appropriate.

For those that subscribe to Fly Fisherman magazine, there is a short article on it in this month's issue.  FFF also has some information on their web site. It may be present in other streams in CA, I'm sure DFG and Fisheries would like to know if you come across it.