NE Mason, from what I've heard here on Pond Boss, if it's an otter, it will clean out the pond of all of your fish. I don't know that you can compare them to GB herons.

The first step might be to identify this animal for sure.

There is a good possibility that these things live in those cattails. Getting rid of the cattails may be necessary, but I can't say for sure at this point.

Excerpt from Robert Crais' "The Monkey's Raincoat:"
"She took another microscopic bite of her sandwich, then pushed it away. Maybe she absorbed nutrients from her surroundings."