There is a few big ones around, there are permanant traps set all around Darwin and they remove every one that they catch in what they call the croc management zone which I think is a 50 km radius around Darwin, they average a couple of hundred a year.
Mostly small to medium sized ones, big ones further out of town generally only get trapped or shot if they are causing trouble. Its by no means a free for all to go get one.

cheers gaff