I wish I’d worn kneepads. But then I hadn’t imagined that a riverfly monitoring survey would require this much genuflection. Like the followers of an undine creed, we kneel on the riverbank, bent over the Forth’s secrets. What is her message? How do we understand it?
With me are Patricia Deeney and Geoff Newell, conservation officers from Belfast Hills Partnership (BHP), an environmental charity, and we’re in a wooded glen below Wolf Hill, close to the former mill village of Ligoniel. Like many community groups and angling clubs, BHP uses the riverfly survey (a citizen science protocol) to monitor local rivers.
Riverflies, like mayflies, spend the bulk of their lives as aquatic larvae. Because their presence, and that of other invertebrates, is an indicator of a river’s water quality, the Northern Ireland Environment Agency makes good use of the BHP’s surveys.
Patricia is collecting a sample by kick-sampling and hand-searching, in timed intervals. After disturbing the river’s substrate with her wellied feet, she nets the material that clouds up through the water. Then she rubs down stones from the sample area into her bucket, dislodging anything that might have clung on. We use plastic spoons to transfer the tiny creatures into subdivided trays to identify and count them. Hence our contemplative pose and rapt focus.
At first all I see is a blur of segmented bodies, gauzy gills, legs, antennae and tails. Pulling my attention away from a Gammarus – a diminutive crustacean that tears around like a stock car on a racing circuit – I concentrate on the tails. Three denotes the larva of an “up-wing fly” (Ephemeroptera), a varied group that includes mayflies; two denotes a stonefly larva.
Caddisflies come “cased” or “caseless”. Caseless larvae are naked, but cased larvae are cloaked with grit and debris woven together using threads of silk. I stare at what looks like a crusted pellet of mud, waiting for the larva’s antennae to emerge.
Geoff shows me how to interpret the information. The different species and their abundance become a composite score. Grateful for a good score today – and to get up – we collect our equipment. Now, a final ritual: we pour the Forth’s messengers back into the water.
Under the Changing Skies: The Best of the Guardian’s Country Diary, 2018-2024, is available now at guardianbookshop.com
