Hot wires work about 3"-4" above the edge of a concrete raceway. Mostly
Not sure how I'd do it around a pond like in the OP's pic though.
We had one at a place I worked, completely enclosed by fence and bird wire over the top. Dang thing would sit on the hill and wait until everyone left the raceways for lunch, break or to get a tool or the feed truck, then fly down and walk in gates which were a pain in the butt to close every time we left for a few minutes.
I heard of some facilities that have dogs that "patrol" all day. Mostly border collie types.
Them birds are deadly accurate with that beak too. Imagine an eye getting taken out by one. They can grab a 1.5" minnow at close to three feet, they can hit an eye if they want.
Someone did a study on kingfishers and hatchery fingerlings. 9 a day average. That adds up in a lot of potential profit lost over the course of a season. Imagine how many a heron can eat.
