In all likelihood if the lake has been around for a while, you already have a well established fish community that is self reproducing... In a lake that size, you're going to have to use some different methods than one would use in a small pond; some methods will be the same to evaluate your lake's fish community and its health.
The use of trap nets, gill nets and night electrofishing should give you a good idea of different species and the population dynamics of your lake. As I said, most species will be seft reproducing in your lake. However, in all likelihood, the walleye will not even in a lake of that size. There may be some natural reproduction but not enough to maintain a quality fishery. This may also be the case for northern pike as well. Only a survey of your lake will give you the answers to your questions... Then you can decide on a management plan and if stocking certain species would be involved in that...
