a hatch of flies or fish taking flies

[The Flying Tench]

I was fishing a lake today which contains some good rudd. All pretty dead, but at dusk there was that typical calm and little rings in the middle of the lake. I think most of them were just a fly hatch, with a few genuine rises, but I'm not sure. Is there any way to tell the difference?

[Andy Macfarlane]

If you can't actually tell at the range you're seeing this commotion from, binos and/or polaroids will help you tell the difference. It's not an easy thing to describe.