The native species were LMB, crappie, native bluegill, chinquapin and mudcats.
Sandman, is chiquapin the is the local LA slang for redear sunfish?

If so, I just learned something new.
Are the "mudcats" bullheads or flathead catfish? A large number of flathead catfish could be eating your bigger LMB. Around here a 7 lb. LMB would not be safe with some of the bigger flatheads I've seen.

Since yiou are looking for a trophey bass lake, have you thought about stocking threadfins or a similar type of forage fish with a more fusiform shape. Golden shiners maybe?