Brent, congratulations on the purchase of the pond! And, welcome to the forum...

Some very interesting questions you have!

There are a few things that hit me right off. First, if you are seeing huge numbers of GSH and nothing else in a 10 acre pond that has been around for 50 years plus, it indicates the pond winter kills pretty regularly. GSH are very winter kill tolerant while game fish are not quite so much. This leads me to believe you will need to establish an aeration program and especially one geared towards preventing winter kill. 9 feet deep is not deep enough to prevent winter kill in MN and 12 feet is pushing the limit as well. Aerating a pond of that size can cost some serious $$$$ though... I would make a separate post in the aeration section of the forum to start getting some good advice.

As far as your goals... If you are able to get an aeration system set up that will prevent winter kill, the sky is the limit. A pond that size has lots of carrying capacity and with that, lots of options. before I stocked anything, I would look into what you have in your pond. At 50 years of age, that's a long time for bucket stocking to happen, and only God knows what's in that pond now. As the weather warms, I would start doing some fishing. Especially with a smaller hook, size 8 or 10 and use small pieces of worm. You can also fish small shiners etc to try to gauge the different species and sizes of fish that may be in there.

Bringing the state into your private pond can have negative consequences. Mostly, they may rule the show... They may place restrictions on what you do with your pond if they are placing their fish in it. I would get in writing exactly what you can and cannot do if they stock fish. Who owns these fish after they do their original harvest? Will you have to follow state public water laws after they are done harvesting these fish. They may restrict you being able to stock any other species of fish until after they harvest or perhaps for years afterwards. They may restrict you from fishing your ponds until they harvest. Be very careful...

It will not be difficult establishing game fish into a pond full of GSH. However, they will directly compete with BG and small LMB for food sources. This is just something you are going to have to deal with though, as they are most likely there to stay. You may see as the years go on after stocking game fish and those game fish reproduce and grow in numbers that your GSH population will go down dramatically.

WE will not prevent you from growing quality BG in a LMB/BG pond. If anything, they may help some. But again, before you accept a deal from the DNR, research it and get the restrictions in writing.