i fished a very small pond the a friend of mine owns and in it there where nice sized cats and a large number of small bluegill, no bass...
i suggested that they could control the population of the bluegill by catching alot of the smaller ones and allowing the others "room" to grow and by stocking bass....
we caught a number of the smaller bluegill and they stocked bass and within 3 maybe 3 1/2 years the bass grew, they grew large....
the largest bass that i've caught to date was around 7lbs....
i would follow what cart7 suggested......
i got the below article from the pond management site on the VA DNR website.....
Harvesting
All ponds have a maximum weight of fish the pond can support. In unfertilized ponds, you should be able to harvest up to 40 pounds of adult bluegill (about 120 fish) and 10 pounds of adult bass (about 8 to 10 fish) per acre per year. In fertilized ponds, you can harvest 160 pounds of bluegill (600 to 700 fish) and 35 to 40 pounds of bass (30 to 35 fish) per acre per year.
In new or reclaimed ponds, do not allow bass harvest for at least 2 years after stocking to let the bass mature and reproduce. Bass are easy to catch, and in small ponds it is possible to harvest 70-80% of the bass in 1 weekend of fishing. Harvest 5 to 10 pounds of bass per acre per year. Restricting bass harvest will help keep the fish population balanced (the proper ratio of predator and prey fish). In a balanced pond, 40-60% of the bass should be 12 inches or longer, while 20-40% of the bluegill should be 6 inches or longer. A good rule of thumb for maintaining balanced bass/bluegill populations is to remove at least 4 to 5 pounds of bluegill for each pound of bass removed. Keep all bluegill caught. Most over-population problems are caused by small bluegill, and returning them only adds to the problem.
Removing too many bass usually causes bluegills to become overpopulated and stunted. Overpopulated ponds are full of 3 to 5 inch bluegills that are thin and slow growing. Management options to correct this problem include: (1) winter water level drawdowns to increase bass predation on bluegills; (2) stocking additional predators; (3) draining the pond and re-stocking; (4) applying rotenone (fish toxicant) to kill a portion of the population; (5) seining to remove excess stunted bluegills.
Catfish and trout can be harvested without limits in ponds because their populations are maintained by stocking, not reproduction.
Hope this helps,
Alfred