Brian C,
There is not much that can be said that is not already posted. A 50 acre lake is difficult to analyize and most likely you need a professional fish sampling project.
This is a guess and will go against the grain of how most managers think.... perhaps you have harvested too many small bass and now the big bass do not have any competition for the available food. If so, they will fill up at night or not have to range far for food.
Excess bream generally means too few preditors.
If you do not have the books already, I suggest you purchase the Pond Management books sold by Pond Boss, they will give you some great insight and will let you develop a plan.
Again, first and foremost, you need to know your fish population.
You can make your own C4 (a bit dangerous and really frowned upon now days) or look in the yellow pages for a local demolition specialist for some red stick. Just remember to throw the stuff into the wind, just last year a guy threw some dynamite downwind and the wind blew his boat over the blast site, it killed him. By the way, the fish biologist can tell when you use red stick on a fish, the air bladder breaks. A guy in Arizona tried to claim the state record with a blasted bass and was arrested.
Good luck
