How to… take a SmartRivers invertebrate sample

How to… take a SmartRivers invertebrate sample

Lauren Mattingley, SmartRivers Project Manager
06 May 2021

April and May is spring sampling time and our SmartRivers hubs are hard at work collecting invertebrate samples for analysis. All hubs are trained to sample to the 3-minute kick-sweep net and 1-minute hand search sampling method adopted by UK regulatory agencies. To achieve as close to this standard as possible, technique is very important.

Below are the key steps hubs are trained to take when taking SmartRivers samples, helping to achieve the most representative samples possible.

Sampling step 1: Divvying up the habitats.

You’ve got three minutes. The first thing you must do is split this time up into twelve 15 second intervals (the 1-minute hand search is separate to this).

Depending on what percentages of substrate, submerged plants and emergent plants are at your site, you assign the sampling intervals to these habitats.

Invertebrates all have different habitat preferences, so missing a habitat = missing species!

Wednesday 01

Sampling Step 2: Get your boots wet

Once you’ve worked out all your habitats and the time you need to spend on each you can get in the river and start collecting your sample.

Depending on the habitat you are sampling there are different techniques you use with the net.

For example, for sampling submerged plants good practice is to:

  • Kick sample underneath the weed at the back end (downstream) to access the fine silt.
  • Sweep the net through the weed to dislodge animals into the net.

Sampling Step 3: Use your hands

Don’t forget the 1 minute hand search! Without this you may miss important caddisfly, snail and leech species.

Sample anything not covered in your 3 minute kick sweep - boulders, tree roots, bricks, even tyres!

Place the item between the flow and the net and gently rub with a gloved hand to dislodge any animals.

Sampling step 4: Preserve for ID

Your sample is now complete, so it’s time to preserve it ready for identification at a later date.

The first step is to sieve off the water, if water remains in the bucket it will dilute your preservative. You may get some material or animals stuck to the sieve, make sure to tap this contents back into the bucket.

Grab the preservative, we use 70% Industrial Denatured Alcohol.

Wash off the sieve into the sample bucket to get any remaining bits, then cover the entire sample, pressing down to ensure everything is immersed.

Seal the bucket and the sample will now last about six months. They can last longer but the longer the sample is left, the greater the chance that the animals may begin to deteriorate.

If you would like to find out more about becoming a SmartRivers hub, please visit the SmartRivers page to register your interest or email smartrivers@salmon-trout.org