One often stated standard for your situation is 500-600 5 inch BG per acre. But for that to work you will need to remove LMB. The LMB have taken up all the carrying capacity of the pond. Removing 30-40 lbs of LMB to start would help. However you need to be sure of the facts first. Do a seine survey and or trapping if you can't have the pond e-shocked. Creel surveys are good but not definitive.