Microscopic wildlife

Recently the Hoopoe blog by NHBS hosted an interview with Ben Fitch, the Riverfly Partnership’s Project Manager.

Ben emphasis how important riverfly monitoring is as an initiative because it is such an effective way of monitoring the health of a river through its fly life. Ben also happens to mention the flat-bodied mayfly larva (Ecdyonurus dispar – Autumn Dun) as one of his favourite river flies, particularly the white-spot variant.

Excitingly during a socially distanced riverfly training session a few weeks ago Alex, Sam and Amy from the Ryevitalise Team found this very variant here in the River Rye. Apparently the exotic looking spots might be caused by a recessive gene, but what triggers it remains unknown.

Riverfly monitoring in the Rye catchment is getting going again now, whilst keeping in line with current Covid-19 restrictions. So we thought we’d have a chat with one of our own riverfly people – Sam Lewsey, Ryevitalise Field Officer.

How long have Riverfly volunteers been out in the Rye catchment this year?

We started the phased return of riverfly monitoring from the middle of June. Amy (Education and Engagement Officer) and myself have been meeting individual volunteers on site to go through revised risk assessments and answer any questions they may have, as well as conducting the first kick-samples of the year. Normally riverfly monitoring would have started up at the beginning of May, but due to restrictions our volunteers understandably weren’t able to get out and monitor for the first 6 weeks of the sampling season.

How many Riverfly volunteers have you got on the Rye?

Currently we’ve got 30 riverfly volunteers registered through the Ryevitalise programme, although not all of these are currently ‘active’; unfortunately due to C-19 we had to cancel our riverfly training and refresher days in April, so some volunteers are still awaiting their official training, including health & safety. Others have received training previously and are in the process of being assigned a site to monitor. Our first phase of volunteers to get back to volunteering were our established riverfly volunteers (8 in total) at sites where they had monitored before.

Riverfly monitoring is a good thing because…
See Catchment Based Approach partnerships website’s explanation of riverfly monitoring

“Riverflies (and other freshwater invertebrates) are at the heart of the freshwater ecosystem and are a vital link in the aquatic food chain. Because riverflies are riverfly populations are affected by many factors, predominately water quality, habitat diversity, water level and flow rate. Their common characteristics of limited mobility, relatively long life cycle, presence throughout the year and specific tolerances to changes in environmental conditions make them powerful biological indicators to monitor water quality, and so are commonly referred to as ‘the canary of our rivers.’  The Riverfly Partnership spearheads an initiative to allow interested groups to take action that will help conserve the river environment. This initiative provides a simple monitoring technique which groups can use to detect any severe perturbations in river water quality…”

Basically this Citizen Science initiative “ensures that water quality is checked more widely [than it would be otherwise] and action taken at the earliest opportunity if any problem are detected”.

Ryevitalise is participating in the national riverfly monitoring scheme run by the Riverfly Partnership. It’s important that we’re part of the wider scheme for several reasons: it standardises the methodology used across the UK; we get top-notch training and support from the Riverfly partnership’s extremely knowledgeable qualified trainers; we can run reports of our results easily from the database that our result go into; and we get to contribute important data on water quality and catchment health to the wider national scheme so that research into trends in the health of our rivers can be carried out and lead to informed changes and positive impacts on terrestrial and aquatic management.

Riverfly monitoring focuses on three groups – the up-wing flies or mayflies (Ephemeroptera), caddisflies or sedges (Trichoptera) and stoneflies (Plecoptera).

Such tiny creepy insects are actually fascinating and wonderful because…
See Freshwater Biological Association’s website

• They are a vital link in the aquatic food chain as a food source for fish, birds and mammals
• They are one of the longest lived group of animals on the earth (mayflies have been around for over 3 million years, with the first written reference to them being made over 4000 years ago!)
• Mayfly nymphs are present in the water all year round, and can spend up to two years feeding under the water before emerging as their adult form… but once they’ve emerged they fly for only a few hours (enough time to display and mate) before dying
• Caddisfly larvae are fantastic grazers that clean up old leaves and twigs from the river bed, and sort through sediment as they go
• Caddisfly cases used to be made into jewellery because they are so beautiful!
• Stonefly nymphs are extremely hardy – managing to continue growth even in sub-zero temperatures. They are also able to suspend growth if a river dries up temporarily
• Overall, riverflies are a vital part of both the aquatic and terrestrial food chains, as well as being key players in sorting sediment on the river bed and breaking down waste products like old leaves and twigs