Los Vaqueros because it's as man made as a lake can be. The creek that flows in is tiny, most all of the water is pumped in from the Delta and sucked right out to go other places. There's virtually no downstream flow and so virtually no risk of inbred steelhead issues.

It's also filled with large predatory fish, most of which were introduced intentionally and reproduce naturally in the lake. You'll never, ever get rid of those fish (imagine telling Contra Costa County residents you were going to rotenone it).

Since there's no steelhead issue, and the other predatory fish - which you will never get rid of - are far more effective predators of frogs and salamanders, adding more trout to the mix is inconsequential. If anything, it satisfies the large predatory fish!

So just like reopening the back ponds at Shadow Cliffs to fishing was the right thing to do because closing them saved nothing and protected nothing, planting trout at Los Vaqueros is also the right thing to do.