I used to work at Cowden Air Weapons Range in the early 80's. One of the bains of our life was the crabbers who would transit through the range with little regard for themselves as they knew we would cease fire on their entry.
You would call them up on channel 16 as it was the usual suspects everytime. and they would say just transitting and then procede to pick up a line of pots!!
We lost a lot of hours during the crab season and we didn't have a patrol boat to deter them either.
VEEPS