A: First off, you would be breaking the law if you shot it!
Persuading a heron to look elsewhere for its lunch is difficult, but not impossible. Many people put out model heron decoys in the mistaken belief that the bird is territorial and won’t fish in company, but this doesn’t work.
The obvious answer is to use a tighter gauge of netting as protection from the bird, and this should not detract from the pond’s appearance.
A more sophisticated method is to use an infra-red sensor, strategically positioned round the pond, to trigger a random jet of water to scare the heron.
Another proven deterrent is to employ a foil helium balloon tethered just above the water. Also consider providing sections of large-calibre drainpipe on the bottom of the pond to provide the fish with a safe sanctuary.