Riverfly Census

understanding and improving water quality in UK rivers

The Riverfly Census has evolved... into SmartRivers

The Census used professional monitoring of invertebrates to understand more about the subtle pollutants 'stressing out' our fish.

Although this project has now concluded, we wanted to carry on species-level monitoring across the UK. To achieve this we have packaged the Riverfly Census method up for volunteer groups.

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.

Excellent storytellers

Every invertebrate is unique, thriving in a specific set of conditions. The types of bugs present and absent from a sample indicate what pressures a river may be experiencing.

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 spanned three years. It began in 2015, with 12 rivers across England.

Multiple sample sites were carefully selected on each river.


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 was inputted into Aquascience’s biometric calculator to obtain scores against key stress types.

The data was then evaluated in a whole catchment context to pinpoint likely suspects contributing to river deterioration.


The data was compiled, and is being reported to stakeholders and policy makers, to improve management and conservation of our rivers.

Scroll down to our map to view the local reports and for the link to download the national report.

How do we sample?

Here’s how we use insect samples to find out what’s going on:

Census Process Image 1

A 3-minute kick sweep sample is taken at a river site making sure to survey all the different habitat types.

Census Process Image 2

The sample is pickled using a special alcohol. This preserves the insects so that counting and identification can be done at a laboratory.

Census Process Image 3

The sample is sorted into groups by an expert and the insects are identified to species level using a microscope.

Census Process Image 4

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.

What Did We Find?

The Riverfly Census has produced two main outputs:

A national baseline

Watch this space, we are working hard to generate a national summary of our findings, using the data to drive national policy improvements and influence more robust baselines.

Click below to read our national conclusions & policy recommendations:

Screenshot 2019-05-29 at 10.41.00

Evidence to drive local improvement

In progress, we are currently compiling local information and delivering our results to relevant policy makers and stakeholders. See our map below and keep an eye on our news for release of local reports.

Use the map below to find our local Riverfly Census reports:

Latest Riverfly Census News

Sewin and their habitats

SEWIN AND THEIR HABITATS 10am – 4pm, Monday, March the 30th, 2020 Salmon and Trout Conservation Cymru warmly invite you to their Annual Seminar for 2020 An opportunity to hear the latest developments aimed at stock recovery Lantra, Royal Welsh Showground, Llanelwedd, Builth Wells A light lunch will be provided. Please advise us should you have […] Read More

Dr Cyril Bennett MBE becomes S&TC’s latest honorary life member

We are proud to award Cyril Bennett an honorary life membership of S&TC for his massive contribution to protecting river ecology in general and to the Riverfly Census and SmartRivers in particular. He has been a fly fisherman for 60 years which has stimulated his keen interest in riverfly identification and aquatic ecology. Cyril is […] Read More

Incinerator proposal raises serious concerns

“This proposed incinerator at Barton Stacey in the Test Valley raises serious environmental concerns” Nick Measham, Salmon & Trout Conservation S&TC do not normally comment on local planning issues but the proposed incinerator at Barton Stacey in the Test Valley raises grave national environmental issues: 1. Abstraction in the headwaters of a fragile chalk stream, […] Read More

River Invertebrate App – Status Update

We are aware users of our invertebrate identification app have been experiencing access issues. S&TC apologises for any inconvenience caused. Issued: 17:00hrs 17th Feb 2020 For anyone experiencing the ‘SQL’ error message, or any other issues when using the app complete the following steps. 1. Check you definitely have version 2.4.1 running. You can find this […] Read More

Agricultural Pollution Update – Nov 2019

Government figures show currently only 14% of rivers are classified as healthy….. Government figures show currently only 14% of rivers are classified as healthy and rural areas are impacting 35% of waterbodies (EA, 2015). Evidence from the Riverfly Census has shown the greatest stressors on our rivers are sediment, excess nutrients, pesticides and other toxic […] Read More

SmartRivers Update – Great Stour

This autumn we took SmartRivers to the beautiful county of Kent. Thanks to the generosity of Stour Fishery Association we were able to start working on the Great Stour, an interesting river that begins away from Kent’s chalk downs, yet enjoys the full character of a chalk stream due to significant influxes of groundwater from […] Read More

Riverfly Partnership News

There are many Riverfly monitoring schemes around, so it can be tricky to understand why so many different schemes are necessary. As the population continues to expand, and our dependence on the environment increases, it is more important than ever that we keep a close eye on the health of our water ecosystems. Thankfully, there […] Read More

SAMARCH technical workshop

SAMARCH Technical Workshop On behalf of the SAMARCH project, we invite scientists and fishery managers to attend our technical workshop. REGISTER BY: 30 SEP 2019 https://samarch-telemetry.org/ The event is organised by Salmon & Trout Conservation, GWCT, and Atlantic Salmon Trust. SAMARCH is a five-year project with a grant of €5.8m from the EU’s France Channel […] Read More

SmartRivers is delivering results

The hot dry summer has exposed the stress our rivers are under Nick Measham, Deputy CEO, S&TC To view the full interview click HERE The hot dry summer has exposed the stress our rivers are under – particularly in Southern chalkstreams where algal growth and sediment is choking life to a seemingly unprecedented extent. Once […] Read More

Chalk streams debated in parliament

We always intended the Riverfly Census to be a lobbying document as well as reporting on the science, and this has been an excellent first political outing for it. Paul Knight, CEO, S&TC In a speech during a House of Commons debate on “Degraded chalk stream environments”, Richard Benyon MP cited evidence from S&TC’s ground […] Read More

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