Well, you can buld a couple of tugs, tractor the civillian ships, so they become yours and then scrap them.
Or, if you have a neutral NPR in 4 jumps range, you can set up a colony in their system, put some infrastructure there and shut all other infrastructure runs down (declare all other colonies either stable or source) and hope that the NPR takes care of your problem and at the same time give you a good reason to go to war.