I guess I would like to know what size do they usually reach? How long will they live without venturing into salt water?

Rainman, I'm sure they were put in by someone. My pond is an excavated gravel pit. There is a chance that during a great flood that the creek that borders my property could enter the pond, but haven't seen it yet even though we've had some real gully washers the past couple winters.

Anyway I am excited to find out more about these fish. I will post any new info as I go along this new twist in my pond journey.