Green-Backed Heron

For a few months now i have been puzzled by the disappearance of gold-fish from my garden pond. One day there would be seven or eight and the next day none. I would replace, and all would be well for a few months, when suddenly they would all disappear again. I have long suspected a heron of some type, this was confirmed this morning when I got a glimpse of this guy busy poaching, he got three fish while i was watching: