Sexing LMB for the novice without training is difficult. Best way for a novice is to catch the LMB during spawn season and obvious presence of eggs or milt indicates sex.
Your problems of YP and RES will not be great in several years. Numbers of BG could be another story. I predict that any offspring from LMB will eventually result in them being the dominat predator. If you get offspring from LMB and unless you carefully manipulate the fishery, I predict in 6-10 yrs you will have an essentially BG-LMB pond. In my experiences perch do not "THRIVE" in SMALL, weed sparse, ponds for the long term with reproducing LMB unless the fishery is carefully manipulated.
