some guys dont mark them because they will get tampered with or stolen. Even nets set by the DNR with huge orange buoys with a large MN DNR sticker get pulled up and messed with.
I was working for the DNR running fyke nets one time down by Wabasha and our random sampling point put us on one of the islands that was piled high with sand from dredging, making a nice sand beach. Anyway, there was a pleasure craft down the beach about 75 yards with two guys and a woman enjoying the day, watching us set this net. Well we set the net and immediately when we pulled away the two yahoo’s come over to it and start to pull it in.
Saying that I dont know what the laws are about visually marking your nets. I know they have to be tagged for identification purposes.