Riverfly Monitoring

Identifying river flies on the banks of the Fleet
Identifying river flies on the banks of the Fleet

Always keen to help with the work of the Galloway Fisheries Trust, I was excited to take part in an “Anglers’ Riverfly Monitoring Initiative” workshop yesterday in Gatehouse of Fleet. After an introduction to the concept of river fly monitoring (and a comprehensive health and safety brief), we headed up the Fleet to take some samples and analyse them in the sunshine, and within the hour, we soon had nets and tubs which wriggled with invertebrates. These were counted and identified, and we started to run our findings through a basic statistical process which would allow us to “score” the health of the river, all based entirely on the abundance of the beasties we had found.

According to the instructor, some species are very sensitive to the slightest amount of pollution, while others could probably live inside a car battery without any ill-effects. As we divided the stoneflies from the caseless caddisflies, we started to get a picture of the water conditions based on straightforward counts of key indicator species, and it was impressive to find that all of the various samples taken came to roughly the same “rating” – a pretty encouraging response to suggest that the process gives useful, reliable output.

I shared a tray of bizarre insects with Senior Galloway Fisheries Trust Biologist Jamie Ribbens, and over the course of half an hour, we had picked out and examined a phenomenal range of species, including freshwater limpets, worms and mites. Before our very eyes, some of the larger species began to consume some of the smaller ones, and as the water warmed up, several of the larvae began to metamorphose into adult flies, which drifted up from the surface like specks of dust.

As we came down to Gatehouse, Jamie and I stopped to explore a shady pool by the roadside. Some large sea trout slowly waved their tails below us in the peaty brown water, and a gang of smaller herling idled quietly into the deeper water as we crouched down beneath the hazel leaves and peered through the glittering water. My fascination with sea trout continues, and this was more than enough to whet the appetite. I imagined what it would be like to return under cover of darkness, and made a mental note to head back there this summer.

Back in the “classroom”, we looked at some of the prowling beasties through the microscope and undertook a short ID test to check that we had absorbed the information flung at us during the course of the day. I managed to remember the differences between an olive mayfly and a blue winged olive mayfly larva, and I brought home a mound of equipment to help me monitor invertebrate life on my local river.

The scope for this Riverfly Partnership project is extraordinary, and it was fascinating to think that these formerly anonymous insects could be used as a barometer for the health of a river. If scores drop suddenly below a certain threshold, immediate action is required to contact the Scottish Environmental Protection Agency, and since the pollution itself can be relatively short-lived, the abundance (or lack) of invertebrate life is a crucial means of not only assessing how things are, but also how they have been. Regular monitoring helps to identify problems, and aside from being a fun way to spend an afternoon, the process is part of a wider move to create and maintain healthier rivers. I will certainly be “kick surveying” across Galloway over the next few months, and much more is to come on this.


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