Freshwater Invertebrate Sampling Techniques

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Explore the 'why' and 'how' of freshwater invertebrate recording with our FSC BioLinks tutor, Rachel Davies – and join us on a course to stay curious!

Pond dipping is an activity enjoyed and experienced by many, especially as young children. It opens up the mysterious underwater world and captures our curiosity.

Many of us adults will know that finding these underwater inhabitants can still spark the same joy and that pond dipping is not the only method used to find them. Plus, surveying is typically done for research or water quality assessments – not just for fun. Freshwater invertebrates are an essential part of ecosystems, acting as food sources and nutrient recyclers. They are also very useful biological indicators.


What is a freshwater invertebrate?

The term freshwater invertebrate refers to invertebrates that spend at least part of their life cycle in freshwater. This includes invertebrates that we often think of when we think of water, such as dragonflies (Odonata), mayflies (Ephemeroptera), water bugs (Nepomorpha) and water beetles (Coleoptera). However, it also includes other invertebrates that we may not think of immediately, such as fly larvae, chalcid wasps and lacewing larvae.

When looking for freshwater invertebrates, most of us will likely have tried pond dipping at some point in our lives, pulling out pond skaters, water boatmen and many other common pond species. There are, however, many different sampling techniques that can be used for freshwater invertebrates, and these techniques differ based on the body of water being sampled.

Pond Dipping

Damselfly Larvae

Pond dipping is a common method for still waters, such as ponds and lakes. It involves dipping a net into the water and sweeping it through different habitats to take a sample. The sample is then examined in a white tray so invertebrates can be picked out and identified.

When pond dipping, you should ensure you are sampling patches of vegetation. You should also ensure you are sampling different water depths by skimming across the top of the water and plunging the net deeper to survey closer to the bottom. For those who do not own a net, a kitchen sieve can work quite well, especially if they are attached to a long handle.

To find invertebrates dwelling in the substrate at the bottom of a pond, nets can be used to dredge a small area. The sample will need to be carefully examined in a white tray, as substrate-dwelling invertebrates are often well-camouflaged and can be found wrapped up in decaying plant matter. This is a good method for finding certain species of dragonfly larvae.

Kick Sampling

Kick sampling is the most common method used to sample flowing water, such as streams and rivers.
To start, a kick net is held against the riverbed with the water flowing into it. Upstream of the net, the surveyor kicks the riverbed to disturb and dislodge any invertebrates. Dislodged individuals and debris are swept up by the flowing water and trapped by the net.
Another helpful tip when kick sampling is to pick up large rocks from the river bed and gently wash them inside the net to remove anything clinging on tightly.

As the net begins to fill up, it should be emptied into a white tray for sampling sorting, inspection and further identification. The physical kick sampling can be repeated several times in different spots on the riverbed to ensure that the sample is representative.

Direct Searching

Direct searching can be a useful method of surveying for both larvae and adults of many freshwater invertebrates. Submerged items such as stones and logs can be turned and visually checked for invertebrates, mainly larvae. For example, some species of mayfly larvae will cling to the underside of rocks, and caddis fly larvae will often be found clinging to rocks when they are close to pupating.

Marginal or partially submerged vegetation can be checked visually by inspecting parts of the plant protruding from the water’s surface. This is particularly useful for finding dragonfly and damselfly exuviae, or individuals in the process of emergence.

The adults of some freshwater invertebrates can be found by visually searching bankside vegetation and trees close to the water. Individuals, such as adult mayflies or adult damselflies, will often rest on these surfaces- particularly in sunny patches.

Flat Bodied Mayfly, by Charlie Bell

Sweep Netting

Sweep netting can be used to find the adults of some groups, particularly stoneflies and mayflies. Sweep netting involves walking along the riverbank, using a strong net to sweep through the bankside vegetation. The invertebrates caught in the net can then be encouraged into pots for identification. This is a common method used by entomologists to survey various invertebrates, particularly flies- so expect a lot of non-target captures.

Emergence Traps

As many freshwater invertebrates spend only part of their life in water, they will at some point emerge to pursue life on land. Once the insect emerges from water and moults, it enters what is known as the ‘teneral stage’. This can last for a few hours or a few days and makes the insect very vulnerable as its exoskeleton is yet to harden up. Once this stage has passed, the adult invertebrate will be ready to disperse with its hardened exoskeleton and its newly developed colouration.

Emergence Trap on Water

Emergence traps make use of their lifecycle to aid collection - it is much easier to capture adults at the teneral stage before they disperse and become more difficult to find. Capturing the invertebrates at this stage in emergence traps allows us to see them transform into adults and aids identification. Often larvae will use rocks, vegetation or even litter for emergence, so one method takes advantage of this. An artificial object is placed into the water with the intent of larvae using it as a structure/substrate for emergence. A container is then placed above the object. The emerging adults can be collected and examined rather than dispersing off, never to be seen again.

For species that do not use structures for emergence, a canopy can be placed over an area known to house lots of larvae. As the adults then start to emerge, they will become trapped in the canopy and can be identified at a later date.

Emergence trapping requires specialist equipment and knowledge of larval sites and lifecycles. It tends to be used for scientific surveys and conservation programs.

Light Traps

 Light traps, predominantly used by moth recorders, can attract the adults of some freshwater invertebrates, particularly caddisflies, some species of stoneflies and freshwater beetles. In addition, some other odd individuals can often turn up at light traps, so other unexpected visitors might show up from time to time!

Stonefly by Craig Macadam

Get Involved

If you would like to study freshwater invertebrates and try some of these sampling techniques yourself, why not join us for some of our FSC BioLinks courses? We have a range of freshwater courses in 2022 at FSC Bishops Wood in the West Midlands and FSC Bushy Park in the Southeast, all of which are very heavily subsidised. We also have some freshwater-focused Field Recorder Days in the West Midlands, where we will try various techniques mentioned above. These are free to attend, but booking is essential as numbers are limited.

All our freshwater invertebrate courses and Field Recorder Days can be found below:


We've still got plenty more courses to be released this year, and to be the first to hear about them sign up to our newsletter.

We also do lots more than just freshwater invertebrate courses, so have a look at everything we have to offer here.

 Dragonfly Recording