The Riverfly Census was a milestone S&TC project which used aquatic insects to tell us about the of the health of our rivers.
The study used standardised monitoring of aquatic invertebrates to reveal how pollution from agriculture, sewage-treatment works, septic tanks and chemicals from many sources is killing our rivers.
This project has now concluded.
However, our SmartRivers programme carries on this work enabling community groups, trusts and other organisations to benchmark and monitor the health of their own rivers.
Why Survey Riverflies?
Insects (which make up 97% of all animal species) have declined 59% since 1970
This is hugely problematic for wild salmon & trout, who need need healthy water environments to thrive.
But why are aquatic insects so important?
Foundation of life
Small but all-sustaining, insects are food for our wild fish, birds and mammals. Without invertebrates, the food web would collapse.
Long-term health indicators
As nymphs, insects are constantly exposed to the water, sometimes for years. A water sample would only give you river health information for a single point in time.
Every invertebrate is unique, thriving in a specific
We frequently talk about missing flylife and lack of fish compared to the 'good old days', but anecdotal evidence like this has little weight in environmental decision making.
The Riverfly Census was our way of collecting much needed high-resolution, scientifically robust data about water quality in our rivers.
The Census Process
Across English and Welsh rivers, we have professionally sampled and analysed invertebrate life to understand the the water quality issues that need tackling
We use this professional, scientific evidence to campaign for improved protection of our wild waters.
The Riverfly Census has
Multiple sample sites were
Kick sweep sampling was completed in spring and autumn to EA guidelines, at all sample sites.
Sampling and species-level identification were carried out independently by professional external consultants, Aquascience Consultancy Ltd.
Species presence/absence data
The data was then evaluated
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The data was compiled, and is
Use our interactive map above to view the local reports.
How do we sample?
Here’s how we use insect samples to find out what’s going on:
A 3-minute kick sweep sample is taken at a river site making sure to survey all the different habitat types.
The sample is pickled using a special alcohol. This preserves the insects so that counting and identification can be done at a laboratory.
The sample is sorted into groups by an expert and the insects are identified to species level using a microscope.
The list of species present is put into a unique scientific calculator. This gives a value for how much the site is being impacted by five key stressors.