They do get caught eventually mulitple times actually they just don't learn. To stop them all you need is some 60lb test with a bunch of snaggers and cast over there line yank there pole in the water and cut your line and say SORRY

If they look like they can kick your a$$ just throw rocks in the water

or steal there tackle box

or you can call DEM and watch as they show up 4 hours later
I was really just kidding about all that theres really nothing you can do except call DEM and hope they show up before they leave