Are all of the CC that you observe or catch the same size?

One of your pond management factors to consider is; are the CC reproducing in the pond?

If the CC are reproducing, it may be time to start culling some. 4# CC are a good eating size. More importantly, they are now large enough to start eating you large BG and your LMB. I don't believe you want that result.

If you like the fishery balance now, then the CC may be net beneficial. Therefore, if the CC are not reproducing, then I think you still may need to start culling, and then ladder-stock some small CC every second or third year to keep a small, ongoing population in the pond.