Most new species of fish are brought in by birds who ingest fertilized fish eggs in one body of water and deposit them via feces in another. This mode of transplant has a very low success rate, but over thousands of years, healthy populations of fish can evolve. It is also possible that bodies of water were connected many years ago, and geological transformations have isolated a lake or stream from its original watershed, this could in essence create a lake "in the middle of nowhere". Generally speaking, deeper lakes have bigger fish, so if the lake of your dreams is deep, it might just hold the fish of your dreams as well.

at last, a use for biology classes

david