Invertebrates make up 97% of all animal species.

Worryingly, their population numbers in the UK have declined 59% since 1970.

Riverfly Census - Wildfish
Riverfly Census - Wildfish
Riverfly Census - Wildfish
Riverfly Census - Wildfish
Water Pattern - Wildfish

Why is the decline of aquatic invertebrates problematic for wild fish?

1. Foundation of life

Small but all-sustaining, invertebrates are food for our wild fish, birds and mammals. Without invertebrates, the food web would collapse.


2. Excellent storytellers

Aquatic invertebrates live in our rivers for most, if not all, of their lives – sometimes for years. Over this time, they are directly exposed to the conditions of the water.

Every invertebrate species is unique, thriving in a specific set of conditions. So, the composition of invertebrates found can be utilised to indicate the types of water quality stress impacting a river. Because of this, using invertebrates provides insight into river health over a much broader period of time than that of a single-point water chemistry sample.

The Riverfly Census

The Riverfly Census collected high-resolution, scientifically robust data about water quality in our rivers. 

The SmartRivers programme carries on this work enabling community groups, trusts and other organisations to benchmark and monitor the health of their own rivers.

How did it work?


The Riverfly Census spanned three years. It began in spring 2015 and ended in autumn 2017. 12 rivers were sampled across England and Wales.

A follow-up survey was carried out in 2021 to see what, if any, improvements in water quality have occurred.


Species presence/absence data was input into a ‘pressure’ 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 reported to stakeholders and policy makers to help improve management and conservation of our rivers.


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