i truly think its because the older fish are just more wary my friend ...i watched a heron at 5 am dive bombing the beds like an osprey ....
herons are not a night time bird though .....and i have seen really big crappie bolt from the bank in the dark in droves ....
those same spots are void of fish in the daylight in many cases or only a few small fish will be there ....
and yes sometimes its right at dark when they come in ......
i just know the spot i hit well and it gets a ton of metro plex pressuse at dark after work ....
so these fish move in a bit later than in some other spots that are less traveled
or at least thats what i think from what i have seen there ....