I can tell you as a current employee of Sonoma Developmental Center that both lakes are closed to public access at this time. Both lakes are closed to fishing as they are the water supply for the facility. We are slated for closure December 2018 and depending on who takes over what, access may be restored.
I fished Fern lake back in the day as my mother began her state work here in 78. It had many bass, yes were mostly 12 to 15 inches in length. I think part of that was due to lack of bass fishing skills. My father used to fish the lake regularly as well and caught many a catfish there.
Some staff I am told hike the trails to Fern Lake and fish it during off hours. I have not tried to do so myself though.