Hydrionis Data

River Aquatic Insect Richness Dataset

How many families of mayfly, stonefly and caddisfly each standardised kick sample contained, at 2,611 long-record English river sites from 1965: 117,713 observations. These are the orders whose larvae live in the riverbed and cannot leave it, and they are the first thing a river loses when it warms, silts or is polluted. 9,611 of the samples held none of the three at all, and those zeros are the most informative values in the set.

v1.0.0117,713 observations1965–2026

117,713

Observations

2,611

Series

2,611

Subjects

1965–2026

Period covered

What this looks like

One real series from the dataset, and real rows from the head of its published extract. Neither is a mock-up: the rows below are the same rows, unchanged, that are in the file you would download.

EPT family richness at CRANLEIGH WATERS

The longest single series this dataset holds — 137 daily values, one of 2,611. The dataset is not this chart.

Drawn to show the shape and resolution of what the dataset contains, not to make a point about CRANLEIGH WATERS. Gaps are breaks, never interpolated.

View the data behind this chart

Underlying data
Period	CRANLEIGH WATERS (count)
1990	0
1991	1.00
1992	3.00
1994	1.00
1995	3.00
1996	0
1997	0
1998	2.00
1999	3.00
2000	4.00
2001	2.00
2002	3.00
2003	3.00
2004	2.00
2005	4.00
2006	7.00
2007	7.00
2008	3.00
2009	7.00
2010	2.00
2011	3.00
2012	2.00
2013	4.00
2014	8.00
2015	6.00
2016	7.00
2017	6.00
2018	4.00
2019	1.00
2020	1.00
2021	6.00
2022	11.0
2023	4.00
2024	5.00

Sample rows

12 of 637,594 rows Taken from the start of observations-ecosystem-uk-ea-ecology.csv. These are sample rows, not the dataset.

Sample rows from the River Aquatic Insect Richness Dataset extract
`metric_id`	`subject_id`	`subject_kind`	`value`	`censored`	`censor_operator`	`censor_threshold`	`censor_limit`	`censor_reported`	`unit`	`period_start`	`period_end`	`period_kind`	`basis`	`confidence`	`source_id`	`source_ref`	`qualifier`	`superseded`	`retrieved`
ept-family-richness	eco-ea-1000	geography	8	—	—	—	—	—	count	1991-07-29	1991-07-29	day	calculated	high	uk-ea-ecology	INV_OPEN_DATA_TAXA.csv	—	—	2026-08-28
ept-family-richness	eco-ea-1000	geography	9	—	—	—	—	—	count	1995-03-22	1995-03-22	day	calculated	high	uk-ea-ecology	INV_OPEN_DATA_TAXA.csv	—	—	2026-08-28
ept-family-richness	eco-ea-1000	geography	6	—	—	—	—	—	count	1995-10-17	1995-10-17	day	calculated	high	uk-ea-ecology	INV_OPEN_DATA_TAXA.csv	—	—	2026-08-28
ept-family-richness	eco-ea-1000	geography	7	—	—	—	—	—	count	1996-04-03	1996-04-03	day	calculated	high	uk-ea-ecology	INV_OPEN_DATA_TAXA.csv	—	—	2026-08-28
ept-family-richness	eco-ea-1000	geography	10	—	—	—	—	—	count	1996-06-27	1996-06-27	day	calculated	high	uk-ea-ecology	INV_OPEN_DATA_TAXA.csv	—	—	2026-08-28
ept-family-richness	eco-ea-1000	geography	8	—	—	—	—	—	count	1996-10-10	1996-10-10	day	calculated	high	uk-ea-ecology	INV_OPEN_DATA_TAXA.csv	—	—	2026-08-28
ept-family-richness	eco-ea-1000	geography	3	—	—	—	—	—	count	1997-03-12	1997-03-12	day	calculated	high	uk-ea-ecology	INV_OPEN_DATA_TAXA.csv	—	—	2026-08-28
ept-family-richness	eco-ea-1000	geography	8	—	—	—	—	—	count	1997-07-14	1997-07-14	day	calculated	high	uk-ea-ecology	INV_OPEN_DATA_TAXA.csv	—	—	2026-08-28
ept-family-richness	eco-ea-1000	geography	11	—	—	—	—	—	count	1997-09-30	1997-09-30	day	calculated	high	uk-ea-ecology	INV_OPEN_DATA_TAXA.csv	—	—	2026-08-28
ept-family-richness	eco-ea-1000	geography	7	—	—	—	—	—	count	1998-04-21	1998-04-21	day	calculated	high	uk-ea-ecology	INV_OPEN_DATA_TAXA.csv	—	—	2026-08-28
ept-family-richness	eco-ea-1000	geography	8	—	—	—	—	—	count	1998-07-28	1998-07-28	day	calculated	high	uk-ea-ecology	INV_OPEN_DATA_TAXA.csv	—	—	2026-08-28
ept-family-richness	eco-ea-1000	geography	11	—	—	—	—	—	count	1998-09-30	1998-09-30	day	calculated	high	uk-ea-ecology	INV_OPEN_DATA_TAXA.csv	—	—	2026-08-28

Download these rows as CSV — the same twelve, with the column header, for testing a loader before committing to the full file.

Methodology

Derived by Hydrionis from the Environment Agency’s published taxon lists for each three-minute kick sample. Every record is rolled up to its family through the Agency’s own taxon dictionary before distinct families are counted, because analysts identify to mixed ranks — 1.1 million records to family, 734,000 to species, 261,000 to genus — and counting raw taxa would measure the depth of identification rather than the river. 484 of the 487 EPT taxa in the dictionary resolve to a family; the three that do not are the order-level entries, recorded when an analyst identified no further than "a caddisfly", and they contribute nothing. Every sample that was taken and analysed carries a value, so a sample containing no EPT is held as zero rather than omitted. The taxon lists themselves are read and discarded; none is stored.

What this dataset cannot tell you

Read before relying on these figures

A count of families, not of insects. One mayfly and four hundred both count once, so richness and abundance can move in opposite directions in the same sample.
Counted at family rank throughout. Species-level richness would be a different and larger number, and the two must not be compared. Total abundance is published by the Agency and is not held: a three-minute kick is designed to find what is present rather than to count it, and the published values reach 333,372 individuals in one sample against a median of 79.
A low ceiling. Britain holds only about thirty EPT families and the observed maximum is 23, so a change of one or two families is within the variation between visits and only a sustained shift means anything.
Strongly seasonal, like the indices from the same samples: spring and autumn communities differ, and a comparison mixing them will find the calendar rather than the river.
Describes the sampled reach, not the river, and conditions can differ sharply above and below a discharge or a weir.
Sites with short records are excluded, so any national picture describes long-monitored sites, which the Agency chose for reasons and which are not a random sample of English rivers.
No dragonfly series is held. The taxon lists contain Odonata and a richness series was computed and refused: a three-minute kick sample is not a dragonfly survey, and the median sample containing any Odonata holds exactly one taxon against a maximum of nine across six decades.

Coverage

Subjects	Environment Agency river macroinvertebrate monitoring sites in England with a long record — 2,611 held
Period	1965–2026
Units	count
Update cadence	Irregularly, when the publisher releases
Identifier	`river-aquatic-insects` v1.0.0

Fields

Data dictionary →

Every metric this dataset carries, with the unit it is stored in and the geography level it is reported at. Full definitions are in the data dictionary.

Identifier	Field	Unit	Reported at
`ept-family-richness`	EPT family richness Number of distinct mayfly, stonefly and caddisfly families recorded in a standardised three-minute kick sample.	count	monitoring-station

Rights and access

Licence position

Open with attribution. Derivative use true; redistribution true; commercial reuse true.

Permitted uses

Public display
Derived analysis
API delivery
Bulk download
Commercial use

Available to: Public, Developer, Research, Professional, Enterprise. These follow from the rights of the contributing publishers, not from a Hydrionis pricing decision — no access tier can widen what a publisher withheld.

Contributing sources

Environment Agency — Ecology and Fish Data Explorer — freshwater macroinvertebrates (Open Government Licence v3.0)

Attribution and citation

Cite and reuse →

Two different obligations, deliberately kept apart. One is a condition of somebody else's licence; the other is a request Hydrionis has no standing to enforce.

Attribution you are required to give

These are conditions of the licences the underlying data is published under. They are obligations to the publishers, not to Hydrionis, and they apply to you directly whether or not you mention Hydrionis at all.

Contains public sector information licensed under the Open Government Licence v3.0.

Environment Agency — Open Government Licence v3.0 (licence text)

Suggested citation for Hydrionis

Hydrionis (2026), River Aquatic Insect Richness Dataset, version 1.0.0, accessed 2026-09-02, hydrionis.com/data/datasets/river-aquatic-insects/

Cite Hydrionis where you rely on the compilation, the normalisation, the eligibility judgements or a chart. Where you use an unmodified published value, the publisher’s attribution is the one that is required; crediting Hydrionis as well is welcome and is not something Hydrionis can require of you.

Recommended, not required. Hydrionis does not claim rights over unmodified public data it relayed, and doing arithmetic on somebody else’s measurements does not make them Hydrionis’s. Cite the version and the access date: River Aquatic Insect Richness Dataset changes as publishers release and as methods are revised, and a citation without both cannot be checked later. Full guidance is on cite and reuse.

Changelog

Version 1.0.0 — 2026-08-28

First release.

Additions

EPT family richness at 2,611 long-record English river sites, from 1965.

Use this data

Download ecosystem observations from EA ecology (637,594 rows) (CSV)
Machine-readable JSON /api/v1/datasets/river-aquatic-insects.json
How to cite this, and who you must credit
How these figures were produced
Request this at a different scale, format or geography

Every bulk extract ships with a companion metadata file carrying this dataset’s version, its sources, their licences, the attribution you are required to give and the suggested citation — so the terms travel with the file rather than staying on this page.

About this data

The fields a professional user needs to judge whether this is fit for a particular purpose. Deliberately not a score.

About this data

Everything below is a property of the data rather than a rating of it. There is deliberately no single confidence score: how much a gap matters depends on what you are about to do with the series, and only you know that.

Source	Environment Agency — Ecology and Fish Data Explorer — freshwater macroinvertebrates · Open Government Licence v3.0
How the values came to exist	Mixed across the series — the basis is recorded on every individual value.
Period held	1965–2026
Known gaps	A count of families, not of insects. One mayfly and four hundred both count once, so richness and abundance can move in opposite directions in the same sample. Counted at family rank throughout. Species-level richness would be a different and larger number, and the two must not be compared. Total abundance is published by the Agency and is not held: a three-minute kick is designed to find what is present rather than to count it, and the published values reach 333,372 individuals in one sample against a median of 79. A low ceiling. Britain holds only about thirty EPT families and the observed maximum is 23, so a change of one or two families is within the variation between visits and only a sustained shift means anything.
Continuity	Version 1.0.0, released 2026-08-28. 1 recorded version; breaking changes and corrections are listed in the changelog above.
Last read from the publisher	2026-08-28 · publisher updates irregularly, when the publisher releases
Redistribution	Permitted by the upstream licences
Commercial reuse	Permitted by the upstream licences. No Hydrionis access tier can widen this.
Methodology	How this was produced