SP " It looks like hunger can be a powerful incentive."

No question about that. They will eat about anything rather than starve.

I have seen LMB adults trained to feed starting with minnow/fish parts followed by minnow parts stuffed with pellets followed by pellets dipped in minnow parts juice followed by just pellets. That pond had little forage also. It was labor intensive and took time and quite a few minnows.