Has the CPU (catch per unit effort = time needed to catch the same # of fish) gone down? If so how much ? If yes then start adding large ( > 4 inches)BG and keep every crappie you catch. The numbers of fish ( 10 lbs , or 50 lbs) per acre depends on the ponds fertility/productivity. If you keep adding BG (up to the right amount) and feed them in conjunction with removing LMB and crappie you can balance the population.