How to record freshwater invertebrates for citizen science

By Making a simple kick net for stream surveys
Comments 35
21 Jul 2026

How to record freshwater invertebrates for citizen science

Why freshwater invertebrates are worth your time

Mayflies, caddisflies and their neighbours are the most practical window we have into the health of a brook or stream. They spend months or even years underwater before emerging as adults, so they experience everything the water does: every sewage overflow, every pulse of silt washed off a field, every summer drought that drops oxygen levels. A chemical reading is a snapshot taken on one afternoon. A sample of invertebrates is a summary of weeks of conditions, written by the animals themselves.

The good news is that you do not need a laboratory or a biology degree. With a net, a white tray and a notebook, you can produce records that genuinely help conservationists, river trusts and researchers understand what is happening to local waterways.

What you are likely to find

Most freshwater invertebrates you meet in a UK brook fall into a handful of recognisable groups. Learning half a dozen of these will carry you a long way.

Mayfly nymphs — delicate, with three tails (sometimes two) and plate-like gills along the sides of the abdomen. Mostly sensitive to pollution.
Stonefly nymphs — flatter, with two tails and wing buds. Usually found in faster, cleaner, cooler water.
Caddisfly larvae — many build portable cases from sand, gravel or plant fragments; others spin silk nets. Very varied, and a delight to watch.
Freshwater shrimp — Gammarus, curled sideways when they swim, often abundant in clean chalk streams.
Water lice — flatter, grey, scuttle rather than swim, and tolerate poorer water than shrimp.
Leeches, snails and worms — often more numerous where water quality has suffered.
Non-biting midge larvae — small, worm-like, often red or green, and famously tolerant of low oxygen.

You do not need to identify everything to species. Getting confident with family level is genuinely useful, and it is the level most river-monitoring schemes use.

Kit, timing and safety

A basic kit is inexpensive and fits in a rucksack: a D-frame kick net with a fine mesh, a white sorting tray, plastic spoons or soft forceps, a pipette, a hand lens of at least ten times magnification, and a waterproof notebook with a pencil.

Sample from late spring through early autumn, when flows are lower and life is abundant. Avoid the days right after heavy rain, when everything is flushed downstream.
Go in pairs, and tell someone where you are going and when you expect to be back.
Wear wellingtons or waders with decent grip, and never wade in fast or deep water. A knee-deep spate can knock an adult off their feet.
Cover any cuts on your hands before you start, and wash your hands thoroughly afterwards — leptospirosis is rare but real.
Practise good biosecurity: check your kit for mud and plant fragments, clean it, and let it dry completely before visiting another river. Invasive species travel on damp nets.

How to take a sample

The standard approach is a three-minute kick sample, and it is easy to do well. Stand facing upstream and hold the net firmly against the riverbed, with the mouth of the net facing into the current. Disturb the gravel and stones immediately in front of the net with your heel for about three minutes, working across roughly a metre of riverbed. The current carries dislodged animals into the net.

Then tip the contents into your white tray with a little clean water and let it settle for a minute. Against a pale background, movement gives the animals away. Sort gently with spoons or a pipette rather than fingers, and return everything to the water at the same spot when you have finished.

Keep your method identical each visit — same stretch, same three minutes, same net — and your records become comparable over time, which is what makes them valuable.

Recording what you find

A record without context is much less useful, so note the following every time:

Date, start time and a grid reference or precise location description.
Weather on the day and rainfall over the previous 48 hours.
Water clarity, approximate flow, and whether the bed is gravel, silt, sand or bedrock.
The method used and the effort involved — for example, three-minute kick sample.
An abundance score for each group rather than a raw count: present, few, several, many. This is quicker and less error-prone than tallying hundreds of shrimp.
A photograph of your tray, which lets a more experienced recorder check anything uncertain.

Write your notes in pencil at the waterside if you can. Memory is unreliable once you are back in the car.

Sharing your records so they count

Records that stay in a notebook help nobody. Send yours to your county recorder for the relevant group, to your local environmental records centre, or to whichever scheme your local river group uses. Many river groups run monthly monitoring and will happily train a beginner; joining one is the fastest route to confidence, and you will learn more in an afternoon with an experienced recorder than in weeks of reading.

Do not worry that your identification might be wrong. Flag your uncertainties honestly, and recorders will treat the data accordingly. A steady series of simple, well-documented samples from one brook, repeated month after month, is exactly the kind of evidence that has alerted people to pollution incidents and helped make the case for restoring a stretch of river. Your local stream is under-recorded far more often than you would think.

Ecology

Dealing with litter and fly-tipping in local brooks

Willow spiling, coir rolls and brushwood bundles can reduce erosion while allowing natural riverbank vegetation to recover over time.

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5 Comments

Robert Sonny says Jul 21, 2024 at 10:00am

I must explain to you how all this mistaken idea of denouncing pleasure and praising pain was born and I will give you a complete account of the system
Reply
- John Abraham says Jul 21, 2024 at 10:00am
  
  I must explain to you how all this mistaken idea of denouncing pleasure and praising pain was born and I will give you a complete account of the system
  Reply
  - Robert Sonnysays Jul 21, 2024 at 10:00am
    
    I must explain to you how all this mistaken idea of denouncing pleasure and praising pain was born and I will give you a complete account of the system
    Reply
Robert Sonny says Jul 21, 2024 at 10:00am

I must explain to you how all this mistaken idea of denouncing pleasure and praising pain was born and I will give you a complete account of the system
Reply

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