Summer sampling guidance

While most of us love the sunshine and warmth of summer, and it is delightful to spend a couple of hours riverside on a sunny day, the invertebrates we sample would rather have cooler waters and shade. We’d like to share some summer sampling best practice with you to keep our invertebrate friends happy and healthy. As monitors, we need to try to minimise stress to the invertebrates from higher water temperatures and oxygen depletion in shallow trays. Some behaviours to watch out for:

• stoneflies doing ‘press-ups’ — they do this because they are trying to extract more oxygen from the water by passing the water over their gills (example videos here and here).

• stone-clinging heptageniids overturning and becoming listless.

These behaviours indicate the invertebrates are becoming stressed, possibly due to heat, and the water is becoming oxygen-depleted.

To try to minimise any stress to them once you’ve retrieved your sample from the river, set up your sorting trays in a shaded area if possible and try to be as quick as you can with the sorting and counting. For example, once your bucket is emptied into the large white tray, you could refresh your bucket with some river water (keep it shaded), and as you do your sorting into the small 8 segment tray, keep a running tally and return those inverts to the refreshed bucket periodically. This will minimise the time they spend in the shallow ‘chip and dip’ tray and avoid overcrowding. If you have any questions about this or have some tips and tricks you’d like to share, then do drop us a line.