4f4c4942-4343-5764-6473-313135353833 English Natural Resources Wales (NRW) Maes-y-Ffynnon, Penrhosgarnedd, Bangor, Gwynedd, LL57 2DW, Wales enquiries@naturalresourceswales.gov.uk http://naturalresources.wales/?lang=en 2026-03-03T16:13:18.21Z NRW 1.0 wel British National Grid (EPSG::27700) Distribution of the Invasive Non Native Species (INNS) American slipper limpet Crepidula fornicata in Conwy Estuary (2012) Distribution of the Invasive Non Native Species (INNS) American slipper limpet Crepidula fornicata in Conwy Estuary (2012) 2013-08-09 NRW_DS115583 The Menai Strait and Conwy estuary area is a designated Special Area of Conservation (SAC) in Wales. The Habitats Directive establishes that the management of SACs should aim to achieve the favourable conservation status of habitat and species features listed within its Annex I habitats and Annex II species. Crepidula fornicata, the American slipper limpet is an invasive non native species in Wales. The slipper limpet occurs on a variety of substrates, it is often found attached to the shells of mussels, Mytilus edulis as well as oysters, stones and other shells around the low water mark. This species is found in south Wales, especially the Milford Haven area, with few records north of the Haven. The Menai Strait mussel fishery in north Wales is the largest in the UK. The mussel ‘seed’ is imported from outside the area. The problem with importing the seed from elsewhere is that there is the risk of accidentally introducing the invasive slipper limpet. This was the case in 2006 when C. fornicata escaped into the Menai Strait. The purpose of this data capture was to assess spread of Crepidula fornicate in North Wales by assessing the Conwy estuary. The Menai Strait and Conwy estuary area is a designated Special Area of Conservation (SAC) in Wales. The Habitats Directive establishes that the management of SACs should aim to achieve the favourable conservation status of habitat and species features listed within its Annex I habitats and Annex II species. Crepidula fornicata, the American slipper limpet is an invasive non native species in Wales. The slipper limpet occurs on a variety of substrates, it is often found attached to the shells of mussels, Mytilus edulis as well as oysters, stones and other shells around the low water mark. This species is found in south Wales, especially the Milford Haven area, with few records north of the Haven. The Menai Strait mussel fishery in north Wales is the largest in the UK. The mussel ‘seed’ is imported from outside the area. The problem with importing the seed from elsewhere is that there is the risk of accidentally introducing the invasive slipper limpet. This was the case in 2006 when C. fornicata escaped into the Menai Strait. The purpose of this data capture was to assess spread of Crepidula fornicate in North Wales by assessing the Conwy estuary. 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 Species distribution GEMET - INSPIRE themes, version 1.0 2008-06-01 geonetwork.thesaurus.external.theme.httpinspireeceuropaeutheme-theme non-native species limpets slipper limpet crepidula fornicata Conwy estuary Menai Strait and Conwy Bay SAC NRW Thesaurus 2023-12-31 geonetwork.thesaurus.local.theme.converted_nrw-keywords Sediment grain size parameters Sedimentary structure SeaDataNet Parameter Discovery Vocabulary 2021-01-06 geonetwork.thesaurus.external.theme.rdf+xml Integrated Public Sector Vocabulary 2013-04-03 geonetwork.thesaurus.external.theme.subjects NRW SMNR Vocabulary 2023-12-27 geonetwork.thesaurus.local.theme.converted_nrw-smnr-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. English biota SeaVoX Vertical Co-ordinate Coverages 2021-01-06 unknown Wales (WLS) -3.93624858 -3.75918269 53.18735314 53.32691663 2013-08-08 2013-08-09 NRW Conwy Estuary Crepidula Fornicata Survey August 2013 Documents The data archive consists of: [A] Report and proformae for recording at both the intertidal and Subtidal sites in word [B] Spreadsheets [C] Photographs in jpeg format of quadrats and of the site in general [D] Marine Recorder file 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 Intertidal Sampling The mussel beds were sampled between 8th August and 9th August 2013 during the early morning low tides. 34 random site locations were chosen and at each site 3 x 0.25m squared quadrats were sampled giving a total of 102 quadrat samples. The substratum, mussel percentage, barnacle percentage and presence of C. fornicata were recorded on a proforma recording sheet. Site locations were recorded using the GPS and then imported into the GIS software package, MapInfo. A number of photos were taken on site. Pictures included general location views together with pictures of quadrats and other subjects thought to be relevant at the time of survey. Subtidal Sampling A 0.1m squared day grab was deployed from Mersey Guardian, an Environment Agency survey vessel, at each site. The day grabs were originally organised for Water Framework Directive monitoring. In some cases however, the grab jaws were not able to shut fully due to the substrate being coarse (cobbles, gravel and sand with many large mussels) and jamming the grab. In these unusable grab samples, hand searching through the material was conducted quickly, specifically looking for C. fornicata. 33 of these grab samples were checked for the invasive species. Intertidal Sampling The mussel beds were sampled between 8th August and 9th August 2013 during the early morning low tides. 34 random site locations were chosen and at each site 3 x 0.25m squared quadrats were sampled giving a total of 102 quadrat samples. The substratum, mussel percentage, barnacle percentage and presence of C. fornicata were recorded on a proforma recording sheet. Site locations were recorded using the GPS and then imported into the GIS software package, MapInfo. A number of photos were taken on site. Pictures included general location views together with pictures of quadrats and other subjects thought to be relevant at the time of survey. Subtidal Sampling A 0.1m squared day grab was deployed from Mersey Guardian, an Environment Agency survey vessel, at each site. The day grabs were originally organised for Water Framework Directive monitoring. In some cases however, the grab jaws were not able to shut fully due to the substrate being coarse (cobbles, gravel and sand with many large mussels) and jamming the grab. In these unusable grab samples, hand searching through the material was conducted quickly, specifically looking for C. fornicata. 33 of these grab samples were checked for the invasive species.