You need to assess the LMB and BG populations. Usually a LMB heavy/crowded pond will have lots of 8-12 inch LMB , a few large BG and very few BG in the 2-4inch size. The small LMB will be in poor condition (not fat).

Removal of crowded LMB is needed if that is the case. You can help the process by adding some adult BG to help with reproduction. Xmas trees near the BG beds (< 40 ft) help survival of offspring. In the proper situation feeding and fertilization can also help.

See this archive thread and its links on stunted LMB ponds - http://www.pondboss.com/forums/ubbthreads.php?ubb=showflat&Number=92500#Post92500

And this one on population analysis - http://www.pondboss.com/forums/ubbthreads.php?ubb=showflat&Number=92492#Post92492