Fresh and cured mackeral are good, but hard to beat good ole bloody chicken livers for channels. Blues and Flatheads prefer live bait and are the exceptional catch, channels are the most prevelant here in So. Cal. Cats feed by smell, so if it stinks or gives off lots of blood or scent trail, it'll work.
I've caught cats on everything from Hot dogs to blood worms, just keep trying till ya find what they like, but liver is my goto bait.