…a blog written by Buglife Cymru, Nature am Byth, Scarce Yellow Sally Conservation Officer, Sarah Hawkes.
The results are back!
Can anyone can remember when we promised an update on the eDNA sampling of the River Dee? It was an awfully long time ago, way back in 2024!?
Much later than originally planned, we’re delighted to provide an update. We’ve tackled many obstacles to progress ranging from fieldwork commitments to asbestos removal work near the lab where the preparation of samples was due to take place. Through to finally finding time for the analysis back at Derby, because the asbestos crisis meant that the work now clashed with university teaching time ….we think it’s been worth the wait!
Dr Alessia Bani and her colleagues at Derby University and Essex University have done a sterling job and revealed some very interesting data. I am pleased to say my background worries about ‘missing the window of opportunity’ because ‘Sally would already have clambered out of the river to become an adult,’ and wondering ‘how on earth could a snitchy bit of DNA, from a tiny insect, be found in a large fast flowing river’ and ‘what if we had done it wrong?’ (which, given Dr Alessia’s clear and simple lessons was unlikely) were thankfully all unfounded. In the event, we think we may have hit a ‘sweet spot’ of opportunity for taking water samples, exactly at the time when Isogenus were moving actively in the river to reach the bank and so shedding more DNA into the water flow.
Incidentally, my findings this year from collecting exuvia (the shed skin of insects after a moult) regularly in a pre-determined place seemed to support the ‘sweet spot’ theory idea. There has proved to be a two week period during which new exuvia are appearing on the bridge arch I have been studying this year at Bangor on Dee. This period of emergence from the river seems to have coincided pretty closely with our two weeks of eDNA sampling last year.
Out of the 12 sites we sampled, an amazing 10 of them showed positive for Scarce Yellow Sally (Isogenus nubecula). Furthermore, DNA was detected both upstream and downstream of the sites where we actually found larvae and adult Isogenus during other surveys. So, I am relieved to say that it cannot be the case that DNA is being carried in the flow from our known sites.
Of special interest is the detection of a strong DNA signal in a tributary, the River Ceiriog, a short way upstream from ‘Riversmeet’, where the Ceiriog meets the Dee.
With this new information available, we are now gathering as much data as possible in the 2025 short survey window for adult stoneflies. During April and May, some lovely volunteers and I, are searching the banks and fields for stoneflies on most sunny days and recording whatever we see of Scarce Yellow Sally. Additionally, our fence post survey (Search for the Scarce Yellow Sally) is running until June to collect any public sightings.
Any information is going to be precious, given how little we know about the “Sally’s” habits and how difficult they are to locate.
Main Image Credit: eDNA filtering © Will Hawkes