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Sampling Techniques

There are a number of different techniques you can use to collect your invertebrate sample. Each type of sample targets a different habitat zone, and by sampling each zone you should get a representative collection of invertebrates from your waterway.

Kick sample

This technique samples aquatic macroinvertebrates that are bottom dwellers, found on rocks and in the sediment and mud of the benthic zone. It is best used in running water.

• Select an area within the waterway that is shallow enough to stand in (ideally knee deep).
• Establish a clear path of 5 metres that can be walked upstream, in a straight line.
• Begin by facing down stream and submerge your sampling net so that it is positioned directly in front of your feet, on the floor of the river bed, with the mouth of the net facing upstream.
• Shuffle and kick the ground so that the sediment/mud/rocks are disturbed; the flow of the water will wash dislodged invertebrates into the net. Try not to collect too much mud, silt or organic matter.
• Slowly walk backwards as you continue this process, for a distance of 5m.

      Rock and Log Sample

Rock and log sample

• You may also wish to pick up smaller rocks and logs that you come across in your path, and rub the surfaces to remove any invertebrates that may be clinging onto the substrate eg. stonefly nymphs. Make sure you collect this material in your net and be careful for sharp edges or foreign material.

Vegetation Sample

• Beat and scrape your net against the base and stems of aquatic plants to dislodge those invertebrates that like to live in the reed zone.

Open water sample

• In slow moving water and pools, sweep your net across the surface and drag it through the water in a figure of 8 motion. This method covers the surface zone and the deep zone.

Sorting Techniques

1. Half fill your white sorting tray with water.
2. Turn your net inside out and empty your sample into your sorting tray. Wash down the sides of your net with some water to make sure you get your entire sample into the tray.
3. Be careful not to overfill your sorting trays with sediment and leaves, as you won’t be able to see the macroinvertebrates. If necessary, spread your sample over a number of trays.
4. Place your sorting trays in the shade, as macroinvertebrates do not like to be exposed to strong light.
5. If there is a lot of mud in your sample, let it settle for about 10 minutes, this will make it easier for you to find the critters.
6. Pick and sort through the collected material for at least 10 minutes. Some critters are great at camouflage and may take time to find.
7. When you spot an animal, use tweezers, a tea strainer, spoon or pipette to fish it out and place it into the petri dish with clear water from your site.
8. Identify the animals you find using the Aquatic Invertebrate Identification Key (5100kb PDF), Junior Primary Chart (1600 PDF) or the Waterwatch SA Critter Catalogue on-line.
9. Record your findings on the Aquatic Invertebrate Record Sheet (95kb PDF). Please remember to use one record sheet per site.
10. After you have identified all the macroinvertebrates in your sample and have completed the record sheet, return them back to the waterway.

For more information, check out our instructional video:

Critters - Where They Wriggle

This video demonstrates how to collect aquatic macroinvertebrates and why they are useful in water quality monitoring. It was developed for NRM Education's Waterwatch programme by students from Urrbrae TAFE and Urrbrae Agricultural High School.