Could you put game birds on some of the scrub land and rent out to poachers / shooters (not sure correct term)?
I like the fishing idea, shame you can't do that.
Could you start a conservation project? Rare breeds? Arapawa goats (lots of them, they are about to shoot most of them in NZ apparently)? Or a animal rescue centre of sorts?
Ghost hunts, night time treks to spot owls, campsite, caravan park.
Plant xmas trees?
So you don't have a house on it? That is tricky thought you had a farm building