Lake Isabella has a bigger problem then rain, it's dam was condemned and the lake can't be refilled to full pool.
I wrote a article for In-Fisherman titled A Rare Chance for a World Record Bass* when the Isy was producing 18+ lb bass. Isabella has the forage base in both Threadfin, Gizzard Shad, a good trout, golden shiner, bluegill and crappie population. Isabella is fed by 2 rivers the north fork of the kern river is a class 5 white water River at 9,000 to 15,000 fps flow rates in the spring, it's not lack of water for this lake.
Our northern Cal lakes are currently topping out and overflowing the dams with emergency and spectacular water releases at this time, several lakes closed to fishing do to the dangerous conditions. The SoCal lakes are another story, we have had a wonderful January rain fall, no down pours, the lakes at this time are still at historic low water levels but a few more storms and things should change.
When lakes fill the ecosystems have lots of new forage for bass, it's good!
Tom
* book 64, Jan-dec '86