Results

Photo 4. Manor Farm.

Results

The full species lists are presented as an appendix. The results summarised here consist of number of species, abundance and WHPT, N-taxa and ASPT for 2019 through to 2022.

All the significant indices are comparable with previous years. The largest change was at Bishops Sutton where all the scores were down on 2021 but still comparable with 2020. This is very likely to be because of vegetation removal which appears to have affected the inchannel Ranunculus as well as the Fontinalis on the weir steps.

Above Drayton and Manor Farm were practically the same as in 2021, although the significant increase in sand and silt above Drayton might be expected to have caused a larger decline.

Below Drayton showed an increase compared with previous years.

All of the results are within the normal year on year variation except Bishops Sutton where the decline was caused by significant vegetation removal. This normal variation consists of a mix of sampling as well as weather related and biological factors.

Site Date Season # species Abundance Ntaxa WHPT ASPT

Bishop’s Sutton 3/9/19 Autumn 54 2488 38 201.9 5.31 15/9/20 Autumn 46 3035 32 161.8 5.06 22/9/21 Autumn 57 3252 41 225.4 5.50 20/9/22 Autumn 45 1545 33 165.4 5.01

Drayton Farm below settlement ponds

Drayton Farm above settlement ponds 3/9/19 Autumn 41 918 31 160.8 5.19

7/9/20 Autumn 40 1043 34 175.0 5.15 7/9/21 Autumn 48 866 38 198.2 5.22 6/9/22 Autumn 58 1080 40 214.8 5.37 22/8/18 Summer 46 1966 32 149.4 4.67

3/9/19 Autumn 45 1242 33 165.4 5.01 7/9/20 Autumn 43 1772 35 160.8 4.59 7/9/21 Autumn 43 1281 35 168.2 4.81 6/9/22 Autumn 41 2187 32 156.1 4.88

Manor Farm 3/9/19 Autumn 53 2699 38 211.6 5.57 15/9/20 Autumn 47 4894 35 174.0 4.97 22/9/21 Autumn 54 3332 38 200.8 5.28 20/9/22 Autumn 47 3937 37 190.1 5.14

Values showing an increase are highlighted in blue

Table 2. Results summary

Much of the variation in species richness is contributed by single occurrences of species whereas most of the variation in abundance is due to variation of a small number of species. Gammarus counts are summarised below and show a general increase across the sites which might be weather related, the decrease at Bishops Sutton is assumed to have been caused by vegetation removal.

Site Sept 2019 Sept 2020 Sept 2021 Sept 2022

Bishop’s Sutton 928 1606 1708 728 Drayton below settlement ponds 364 440 139 283 Drayton above settlement ponds 159 580 127 393 Manor Farm 1341 3598 1560 3020

Table 3. Gammarus counts