If you are woried about the LMB overpopulating and jsut want a few predators to control things you could add some Euryhaline fish such as red drum, mangove Snapper or southern Flounder. since you are so close the coast you probably could get a couple in the esutaries around you. they can be a little cold sensative but other than that once acclimated over to fresh water they will thrive but not be able to reproduce. I know of a pond here in florida that has 2 nice snook and a couple 20-30" tarpon in it. It has lots of BG in it and they seem to be doing well. You might be too cold for Snook or tarpon but redfish and mangrove snapper can handle the cold a little better.
I just added some to my pond that is in about the same startingpoint as yours. somthing differant to consider.

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