For what its worth, I was dabbling in the edge of the river Don at dusk, on a deep stretch near conisbrough as there was one spot where there seemed to be quite alot of bottom feeding activity. Night fell, too dark, no night lights, packed up.
When darkness really fell the water surface came alive with feeding activity but only when true night was upon the water. It was like someone had turned a light on (??????).
Following night, weather same, same time (maybe different moon phase but dont get me started on that) Not a sausage, no movement.
Possible Conclusion.. You are never guaranteed to 'catch' fish feeding.
There are many factors effecting feeding habits of fish including weather, Dawn, Dusk, Lunar Phases and probably many unknown quantities, However one thing does seem to make sense. Larger, Older, Wiser fish are probably more active at night due to less disturbance from angling pressure.