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Glad tidings from the Gur

I joined Val and Peter on their monthly citizen-science water analysis of Gur Beck (part of the National Trust's 'Riverlands' programme) on Tuesday 21st November. I brought my net and tray and took a look at the animal life in the stream at Sustead Common, as part of the national Riverfly programme. This scores the habitat based on the abundance of river invertebrates found in a timed sample. It was originally designed to enable anglers to detect pollution events upstream, recognising a drop in the score from one month to the next, below a 'trigger level'.  A theoretical maximum score would be 24 but in reality, a clean, lowland river is likely to score 14-16. A dirty or polluted site would be 5 or lower.  At this time of year many individuals are tiny (1-2 mm in size), having been born in late summer and growing up to overwinter for emergence in the spring, so even clean sites will have lower scores of 10-12. We were excited to score 10 at Sustead.  Moreover, the shapes of individuals within some of the eight groups made it clear that there were several species present. I didn't take any samples away for identification to species level because they were too small for me to be confident, but I shall collect some more in the Spring. I shall also be happy to show people the treasures inside the stream when we have a work party at Sustead in the New Year.


David Harper

November 22nd 2023


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