4f4c4942-4343-5764-6473-313235333731 English Natural Resources Wales (NRW) Maes-y-Ffynnon, Penrhosgarnedd, Bangor, Gwynedd, LL57 2DW, Wales enquiries@naturalresourceswales.gov.uk http://naturalresources.wales/?lang=en 2026-01-09T15:39:09.352Z NRW 1.0 wel NONE The status and distribution of Lilljeborg’s Whorl Snail Vertigo lilljeborgi at Pont Croesor on the Afon Glaslyn in 2022 The status and distribution of Lilljeborg’s Whorl Snail Vertigo lilljeborgi at Pont Croesor on the Afon Glaslyn in 2022 Statws a dosbarthiad Malwen Droellog Lilljeborg Vertigo lilljeborgi yn SoDdGA Glaslyn wrth Bont Croesor ar Afon Glaslyn yn 2022. NRW_DS125371 Results of a monitoring survey in August 2022 for the Near Threatened Lilljeborg’s Whorl Snail Vertigo lilljeborgi within Glaslyn SSSI are presented. The area surveyed is north of Pont Croesor on the Afon Glaslyn. Judged to be in Unfavourable condition after the last survey in July 2008 (Willing, 2009), the present survey over two days in August repeated the previous survey. The wetland habitats remain visually very similar to those described in 2008 and weather and river level conditions were similar. All 8 sites were revisited and sampled by visual search, beating vegetation, and collecting bulk samples of decaying plant matter. A 9th site was sampled near Site 7, the point at which V. lilljeborgi was last recorded in 2008. A suction sampler was used in 5 additional locations between sites on the east bank. A total of 12 adults of V. lilljeborgi was found at Site 7 and Site 8, confirming that the species survives on both sides of the Afon Glaslyn, although it is still apparently restricted to small areas. Two juvenile Vertigo were also found at Site 6. These could not be unambiguously identified as V. lilljeborgi, owing to the presence of another species, Vertigo antivertigo, nearby. All Vertigo specimens were found in large bulk samples that had been dried and sieved. No Vertigo were observed in the field, emphasising the importance of multiple sampling methods. Using the Conservation Objective Lower Limit of 10 individuals set by Willing (2009), V. lilljeborgi is judged to be in Favourable condition within Glaslyn SSSI in August 2022. Nonetheless, the population only just exceeds the Lower Limit, and remains small and potentially vulnerable. Further sampling in the areas around Pont Croesor could help determine whether V. lilljeborgi is more widespread on the Afon Glaslyn floodplain. Results of a monitoring survey in August 2022 for the Near Threatened Lilljeborg’s Whorl Snail Vertigo lilljeborgi within Glaslyn SSSI are presented. The area surveyed is north of Pont Croesor on the Afon Glaslyn. Judged to be in Unfavourable condition after the last survey in July 2008 (Willing, 2009), the present survey over two days in August repeated the previous survey. The wetland habitats remain visually very similar to those described in 2008 and weather and river level conditions were similar. All 8 sites were revisited and sampled by visual search, beating vegetation, and collecting bulk samples of decaying plant matter. A 9th site was sampled near Site 7, the point at which V. lilljeborgi was last recorded in 2008. A suction sampler was used in 5 additional locations between sites on the east bank. A total of 12 adults of V. lilljeborgi was found at Site 7 and Site 8, confirming that the species survives on both sides of the Afon Glaslyn, although it is still apparently restricted to small areas. Two juvenile Vertigo were also found at Site 6. These could not be unambiguously identified as V. lilljeborgi, owing to the presence of another species, Vertigo antivertigo, nearby. All Vertigo specimens were found in large bulk samples that had been dried and sieved. No Vertigo were observed in the field, emphasising the importance of multiple sampling methods. Using the Conservation Objective Lower Limit of 10 individuals set by Willing (2009), V. lilljeborgi is judged to be in Favourable condition within Glaslyn SSSI in August 2022. Nonetheless, the population only just exceeds the Lower Limit, and remains small and potentially vulnerable. Further sampling in the areas around Pont Croesor could help determine whether V. lilljeborgi is more widespread on the Afon Glaslyn floodplain. Natural Resources Wales (NRW) Maes-y-Ffynnon, Penrhosgarnedd, Bangor, Gwynedd, LL57 2DW, Wales enquiries@naturalresourceswales.gov.uk http://naturalresources.wales/?lang=en Natural Resources Wales (NRW) Maes-y-Ffynnon, Penrhosgarnedd, Bangor, Gwynedd, LL57 2DW, Wales enquiries@naturalresourceswales.gov.uk http://naturalresources.wales/?lang=en Natural Resources Wales (NRW) Maes-y-Ffynnon, Penrhosgarnedd, Bangor, Gwynedd, LL57 2DW, Wales enquiries@naturalresourceswales.gov.uk http://naturalresources.wales/?lang=en Natural Resources Wales (NRW) Maes-y-Ffynnon, Penrhosgarnedd, Bangor, Gwynedd, LL57 2DW, Wales enquiries@naturalresourceswales.gov.uk http://naturalresources.wales/?lang=en Protected sites Species distribution GEMET - INSPIRE themes, version 1.0 2008-06-01 geonetwork.thesaurus.external.theme.httpinspireeceuropaeutheme-theme whorl snails Glaslyn snails Pont Croesor river Glaslyn (afon Glaslyn) vertigo moulinsiana NRW Thesaurus 2025-01-08 geonetwork.thesaurus.local.theme.converted_nrw-keywords There are no access restrictions on this data. NRW may release, publish or disseminate it freely. no limitations © CNC/NRW Data may be re-used under the terms of the Open Government Licence providing it is done so, acknowledging both the source and NRW's copyright. It is the recipient's responsibility to ensure the data is fit for the intended purpose. Contains Natural Resources Wales information © Natural Resources Wales and Database Right. All rights Reserved. Open Government Licence English biota SeaVoX Vertical Co-ordinate Coverages 2021-01-06 Wales (WLS) -5.777741 -2.608865 51.240829 53.513067 2022-08-22 2022-08-23 Rowson, B. 2022. The status and distribution of Lilljeborg’s Whorl Snail Vertigo lilljeborgi at Pont Croesor on the Afon Glaslyn in 2022. NRW Evidence Report No. 649. Natural Resources Wales, Bangor Database A] Database - Welsh Invertebrate Database B] Documents - Digital versions of the contract report: Microsoft Word document; and an equivalent Adobe Portable Document Format version. Commission Regulation (EU) No 1089/2010 of 23 November 2010 implementing Directive 2007/2/EC of the European Parliament and of the Council as regards interoperability of spatial data sets and services 2010-12-08 This dataset has not been assessed for conformance to the referenced INSPIRE regulation. false Sampling conducted by by visual search, beating vegetation, and collecting bulk samples of decaying plant matter. Sampling conducted by by visual search, beating vegetation, and collecting bulk samples of decaying plant matter.