LA. welcome to the PB forum. An interesting question.

To many BG can be a cause of no/little LMB recruitment as can other factors and usually in combination. Take a look at this link on pages 10-12 on Management (balance) in LMB/BG ponds. A seine survey will tell you much about small fish status. I suggest it as a method to gather more info (in addition to creel(catch) surveys and visual info). If what you think is true, an easy way to deal with it is to buy a few LMB in the size classes that are missing and add them. Population balance is an on going matter in LMB/BG ponds so it is good to learn how to determine it and how to use it to meet your goals. Do you know your original stocking rates from 3+ years ago and any since then?

http://msucares.com/pubs/publications/p1428.pdf

Theo great minds think alike. ;\)