where to find fresh water clams in nor cal

Can anyone direct me to some freesh water clams in the lake and mendo counties?  I would like to just taste the difference between the two.

Thanks
Tom

I did not know fresh water clams were edible??  I know it may not help you much but I have found good numbers of clams in the Russian River just below the surface on a lot of gravel bars and some can be a good golfball size.

When lake mendocino is low there are clam shells everywhere in the mud.  I've never seen any living though and the shells are so small that I'm not sure they would be worth trying to eat.

delta clams?