Thanks Click, Jack and rpt.
Jack, rpt was correct.
I use small pieces of bread that I toss in front of the heron at water's edge to attract the fish. Too far from the edge and he can't reach it (the fish know this and quickly attack the bread which is gone in a second). When I hit the mark within his reach near the water's edge, the fish are much more wary and often won't take the "bait". Then it's a waiting game between the hungry cautious fish and the heron. The smaller fish are more daring and dart in and out to take bites of the bread. The fish can see the heron hovering over the bread so I try not to get it too close to the heron. The heron makes multiple stabs near the bread when the fish rush in. Only occasionally do these attempts result in a catch for the heron. Mostly he gets small ones, but sometimes a slow or dumb big fish pays the ultimate price (often with the bread visible in the fish's mouth). When he catches a fish, he quickly retreats from the water's edge (and me), so that if he drops the fish, it won't get a chance to swim away. To get a close shot, I will chase him sometimes (I think he believes I might be after the fish also). He absolutely will not eat the bread, no matter how hungry. All the other birds I feed at the same time (ducks, moorhens, cardinals, bulbuls, mynah birds) really love eating the bread. The ducks will gang up on the heron and try to steal his bait bread, but will not cross a line about 1 foot from his sharp stabbing beak.
In this photo from yesterday, you can still see the piece of white bread in the fish's mouth.