Has it had water in it this whole time, if so there may be some types of food anyway.
I know that somehow my pond sat empty for 4 years before I stocked it and somehow GSF were already in the pond.
This has made for a fun time, but I have pulled out a few nice GSF to eat. The LMB have taken care of the rest. I am sure I will continue to have them in small numbers, and will end up with some natural HBG, but heck we eat all of them and the kids like to catch them so I guess that is all that matters.