I like to consider myself a bit of a dab hand at catching a weight of small dace, they are the primary target for me in matches on the Gt Ouse around Bedford and the upper Warks Avon (my two main venues throughout the summer months). I can usually catch them even when they are darting around in the upper layers, when lots of anglers struggle.
I’ve also had framing weights of them from the Severn and Wye in to the mid 20s ... although not quite the colossal weights that you sometimes see at Hereford.
On the Trent and Thames I’ve not Seen the same numbers.
In terms of size ... I’m looking at a 4oz fish as a good one, except on the Wye.
On those four dace rivers that I fish there is a common pattern:
1. Relatively short lifecycle , from tiny dace (half to one ounce) to 5 to the pound size in about three years, then two years later bust until the next cycle.
2. Migration from shallows to deeps when the clocks go back. Hence the huge shoals at Hereford in the winter.