Milo has summed it up pretty nicely. I don't fish for sockeye in the Fraser so cannot comment much on that. My guess would be those fish are not caught by biting so timing wouldn't matter that much.
The few times when we fished for chinook salmon by bar fishing with spin n' glow, there isn't a consistent pattern when it comes to when fish are usually hooked. We've hooked fish very early in the morning when we first arrive at the bar. We've also hooked fish in the middle of the day, sometimes late in the day when we are just about to leave.
For the Tidal Fraser River, tide plays a huge role. There's no point fishing at first light if the tide is low, no fish are moving up during that time. A high tide in the middle of the day can be very productive. I also prefer to fish on a very sunny day, not just because I hate fishing in the rain, but light makes the fish see better in the murky Fraser water. If we are to get more technical, tidal difference and the rate of tide movement also influence how the fish are biting.