There are some comments in this thread that just make me shake my head. This is the simplest situation and requires no thought or discussion. Y'all are overthinking this
You own nothing in the public realm - it belongs to all of us and none of us at the very same time
The old golden rule applies here - just treat other people like you would wish to be treated.
I would walk over, introduce myself and let them know the hot lure from yesterday and offer any tips that I had, then move on and find another spot to fish. Who knows - maybe you find a new fishin' buddy out of the the deal?
Society is getting too focused on the legalities and technicalities. Just be a decent person, consider your fellow sportsman and you don't run into issues out there. Be kind and help a guy out, it all comes back around in the end.