As the waters cool and the mayfly activity increases, fish will often move up higher into the riffles than usual. That ankle - calf deep water right up the head, or along the very edge of the riffly water now becomes my target area and anyone who fishes the famous, Mataura river knows: it's the shallowest of the rocky riffles that offer the best nymphing.
Now looking through many anglers fly boxes the majority of their flies sport tungsten beads, however in the best of the autumn riffles, even a 2mm tungsten bead can be too heavy.
Lower Mataura stalwart, David Murray-Orr is a big fan of brass beads for autumn nymphing water, their slightly lesser weight compared to tungsten making them more fishable through the shallows. In addition myself, I’m a big fan of plastic beads of gold, red, and clear coloration, offering very little weight however retaining the suggestion of air / colour / dynamics and all the other benefits of a bead.
However it's the unweighted nymph patterns which feature largely in my late season nymph box, the turbulence and disturbance of the shallow, riffle water often being enough to pull your flies down beneath the surface. I always fish nymphs in tandem / teams and alternate patterns slightly to grab attention and have options.
And don’t think those foam line sippers / swirlers are always feeding on top: often they are keyed in on emergers just beneath the surface... what you see breaking the surface is their follow through. A small, unweighted nymph is just the key here...
Chris' Tip: The key on the Mataura is to keep things small. Sure, there are a few size 14 represented nymphs to be found, but there are a heck of a lot more size 16 and 18's, and so that's what the trout relax in on, and I fill my box with. And never fear - trout will easily see such small flies even in the most turbulent of water and lowest of light... their eyesight and reactions are much better than ours.