In my experience it seems when river dropping off from flood is best time and the most successful, also seems people who catch most are the ones who have the time to fish the rivers when they have dropped to the desired level when the water still holds some colour.Once the colour goes so do the chances of catching.

...ooohh to have the freedom to arrive at the right time eh......only happened to me once due to work though

and i had 12 sea-trout and a salmon.
Ps...should have said, you can catch them on loughs in day light.