Waterstock Mill was surveyed on the 16th of August at mid-day by Ellen Robson from the University of East Anglia, supported by Emily Godfrey from the River Thame Conservation Trust. As part of Ellen’s dissertation project, which aimed to understand the distribution of dragonflies and damselflies (odonates), she carried out multiple surveys including water quality and invertebrate counts.
The River Thame Conservation Trust are very aware of just how rich the Mill site is, and can very easily pin-point it as one of the best sites along the main river Thame. It came as no surprise that the aquatic invertebrate score for this site was the best across the whole of the main river, meaning there is a high diversity of species (including many species of mayfly, caddisfly and freshwater shrimp) which can support a range of different fish species. There was further confirmation of this when the Environment Agency carried out their fish survey and found at least 12 different species to be present.
Along with the in river invertebrates, 8 demoiselle nymphs were found of varying species. Interestingly, across all of the surveys carried out, no dragonfly nymphs were recorded. This is quite a mystery and the River Thame Conservation Trust will be working with some local experts to try and find out exactly where they might be hiding. The lack of nymphs did not mean a lack of flies though, a common darter and brown hawker were spotted along with 4 banded demoiselles and 2 beautiful demoiselles. In what is a very rapid survey, this is a great number of odonates to find and again, shows Waterstock Mill to be one of the best sites on the Thame.
In order to support the great richness and diversity at this site, having good water quality is absolutely key. So, not only did the Waterstock Mill site show us the highest number of invertebrates, one of the highest number of odonates and a great number of fish, it also had the lowest phosphate reading across the whole of the main river.
Ellen will now be working on analysing all of the data that she has collected over the summer, trying to determine the most important factors that affect the odonates in the catchment. The River Thame Conservation Trust hope to continue these surveys yearly, using Ellen’s model, so that we can keep a close watch on changes across the years and make improvements that will mean we see more damselflies and dragonflies across our river.