If you can't do as Eric suggested because you have fish now that need to be moved then use the cage (and feed pellets) and stock a LOT of FH so the #s will be enough to both feed the fish and reproduce enough to establish a population. Like Eric you may well need to add more FH from time to time. I would be hesitant to put that many adult YP in your pond if they are spawning. That could overwhelm the system. Those YP will be beyond predation and continue to reproduce. If you will be feeding pellets to the YP it changes your options as they will not need as many FH.

One suggestion - read Bill's cage articles in PB mag if you have not done so.