ARK Riverfly Monitoring sites - From Clatford - Reading
Latest Riverfly Data
January 2017 Riverfly Data
Encouragingly some scores have started to increase in January 2017, although other sites are still reporting one or more of the following - low river levels, silt, algal growth and poor flow. Olives have been in good numbers at sites including Stichcombe, Stonebridge, Poulton Footbridge and Kintbury Down of Fishing Hut. BWOs have been recorded in greater numbers than January 2016. BWOs usually overwinter at the egg stage in their life cycle however, whilst most eggs are still going into diapause some are hatching to produce another generation. It looks as though the BWO is moving from a single generation with overwintering eggs to towards a second (or more) summer generation, with increasing numbers of overwintering nymphs. So keep a close eye on your olives (swim with a darting motion) and your BWOs (swim very poorly with a rocking motion).

Two species that can be confused with our 8 key indicator species Top right an alderfly larva and bottom right a leptophlebiidae larva. These are NOT counted and don’t contribute to the score but can be noted in ‘other sightings’.
Note the very visible hairy gills on the leptophlebiidae, unlike any of the 8 species we count.
Alderfly larvae can look a bit like mayfly larvae, note the rounder head and lack of prominent tusks on the alderfly larva. It also does not have gills in the same position as the mayfly. The mayfly has rippling gills on its back where as the alderfly gills are on its sides.



map of riverfly sites on the river kennet