Little whirlpool ramshorn snail (Anisus (Disculifer) vorticulus) site summary records, 2018-2020
Citation
Royal Society for the Protection of Birds (2022). Little whirlpool ramshorn snail (Anisus (Disculifer) vorticulus) site summary records, 2018-2020. Occurrence dataset https://doi.org/10.15468/kmen64 accessed via GBIF.org on 2024-12-11.Description
Sampling of 21 ditches(average 118m long) in grazing marsh at RSPB Pulborough North Brooks to record numbers of Anisus vorticulus per sample. Ditches were subject to 4 different management regimes in 2016/17 with 4-5 replicates of each; staggered clearance (alternating cleared and un-cleared sections 10-15m apart), half-width clearance, ends uncleared (ditches <100m long with up to 80m cleared in centre section) and clearance of a narrow channel through the centre of a length of ditch (permitted by NE though not within licence protocol). The ditches were sampled at 144 sampling points each year from 2018-2020 using a standardised sampling regime. Zero counts were included. Numbers per sample were highly variable along ditch lengths and between years and may not represent absolute population sizes. Totals for all 144 sampling points are given against a centroid grid ref for each of the 3 years.
Purpose
The project was established to test the ditch management protocol as determined within the WML-CL14 - Class Licence for maintenance of ditches and other water bodies inhabited by the Little Whirlpool Ramshorn Snail, whereby sections of ditch are left uncleared whilst other sections were cleared.
Sampling Description
Quality Control
Identification of samples of snails was validated by 3 independent conchologists. The sampling regime was subject to a Quality Assurance survey by a different practitioner using a different sampling technique at different sampling points, which established the presence of Anisus vorticulus in the ditches.Method steps
- The sampling technique used was a simplified sweep to detect low density Anisus vorticulus within a sample area, causing as little disturbance as possible to the habitat. Beginning as close to the centre of the ditch as possible, a 0.5mm mesh net was drawn towards the bank in a single sweep, covering 0.25m2 to a depth of 25cm. The vegetation was gently agitated during the sweep, but any surrounding vegetation was disturbed as little as possible. Once the sample was collected, the material was rinsed and then the larger vegetation within the sample was removed and the remainder of the sample was then placed into a white gridded tray and spread out for counting. Only the total number of animals were counted, not the numbers in individual size classes. A single sample was taken at each sample point, with 10 -12 sample points per ditch.
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Bibliographic Citations
Contacts
originatorRoyal Society for the Protection of Birds
metadata author
Royal Society for the Protection of Birds
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NBN Atlas
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Conservation Data Management Unit
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email: dataunit@rspb.org.uk