I haven't met the heron yet that wanted to try to eat fish AND keep an eye out for this...
Not my dog, but I wouldn't dream of having property anywhere without a pair of them. They're better than any alarm system and they work 24 hours a day for just food and a spot on the couch.
Edited to add, raccoons will no longer eat your crayfish either. LOL.
Also...geese are a problem of the past. Basically, anything short of a full grown bull stopping by your pond to drink is going to be chased off pretty easily.