I fished Deer Lk (the lower one at the end of the official trail from Mammoth). No fish, don't recall seeing any.
Also, Pica Lk. Saw fish, didn't catch any. My friend caught one.
Purple Lk, halfway to Virginia, had lots of small fish. Caught a few. Brookies, as I recall.
I also saw trout in the outlet from the uppermost lake just below Duck Pass.
This was mid-September last fall.