Ric:

I would suggest you contact the AZ DFG and ask them if they can do a shocking studying of you lake to determine the population dynamics of your lake. If they can't do this ask them if there are any private companies in your area that can do this.

I bet you will find that the lake is bass heavy and you need to start culling out bass, if you want to increase their sizes. Do people keep bass out of the lake? The size of your crappie indicates that the bass are keeping them in check. However, if you aren't catching many bass over than 1 - 2 lb. fish you could be bass heavy and have a stunted population of bass. How often do you see small tilapia? Are you seeing bluegill on beds? Putting out some structure will make it easier to catch the bass for you as you will certain spots that will attract them to.

Dave