The Autumn is probably the best time to fish for pike, as they will be feeding up for the winter, the females feed well at this time to sustain the growth of roe. There's a good article in this months Coarse Fisherman by Mike Brown on this very subject.
As for the dace moving down river, and I supose you mean the Tees, I'm not so sure this happens as much as it did since the barrage was put in. The dace seem to have left the ex-tidal lenght, but still thrive up river where there are still flow and gravels. If they were to drop down they wouldn't have to go down stream as far as Thornaby to find deep water now.
To be honest I'm not sure if the famed dace migration of the tidal day's ever did happen to the extent people thought. Big catches of dace were taken, but this could have been as much to do with the fact that the river was tidal, and changed direction four times a day, forcing the fish to move with it. To move takes energy to get energy they must feed.
Now the roach and bream that like the slow deep water better will be fairly static, so there's plenty for the pike tp munch on, not to mention the sea trout and salmon par runs.
It's strange I've fished the Tees for over thirty years, and before the barrage was put in a pike in the lower reaches was unheard of. However they must have been there. Now the river has the potential in the next five to ten years to on of the best pike fisheries going.