Get a pair of leather gloves and put them on. Then walk up to the poachers, grab 2-3 blue crabs from their bucket (be sure to piss them off), then stuff them down the poachers pants and proceed to push them off the dock.
I have always wanted to stuff a blue crab down someones pants..
Seriously, though - there is a lot of dirtbags that hang out down there. I would think the NPD would be interested in getting involved and maybe find a few outstanding warrants.