I have a large pond in my back yard with a few goldfish and shubunkin ones as well. There are several lily pads throughout the pond for the fish to hide under. Problem is I never see them and it looks as though they have disappeared. At night I take a torch and feed them and then will see one or two, but they don't hang around long if I leave the torch on them. Last winter they were out all the time and I could watch them feeding. How long would they lie low if a heron was occasionally hanging around?

Indefinitely! If the heron didn't already eat most of them. How large is the pond (gallons or dimensions)? Is it deep and do you have shelves where a heron can sit and eat? You need to take measures to heron proof the pond or he will keep coming till the food (fish) runs out.

Good luck

What is the temperature of your water? The fish do hibernate, in a sense, due to cold water below 50 deg.. Does the pond freeze over? Unless you are in a warmer climate,no freezing temps. you should not feed at all in winter. This will kill your fish.
When they settle in for the winter they go to the bottom where the water is warmest.

It's probably just the fact that they r outside they r not inside fish so they may not be happpy with humans