4f4c4942-4343-5764-6473-313232393637 English Natural Resources Wales (NRW) Maes-y-Ffynnon, Penrhosgarnedd, Bangor, Gwynedd, LL57 2DW, Wales enquiries@naturalresourceswales.gov.uk http://naturalresources.wales/?lang=en 2026-03-03T17:09:14.622Z NRW 1.0 wel Latitude and Longitude (EPSG::4326) Survey of distribution and extent of Didemnum vexillum in Holyhead Harbour after Storm Emma October 2018 Survey of distribution and extent of Didemnum vexillum in Holyhead Harbour after Storm Emma October 2018 Arolwg o ddosbarthiad a hyd a lled Didemnum vexillum yn Harbwr Caergybi ar ôl Storm Emma Hydref 2018 2019-07-31 NRW_DS122967 This dataset details the presence and absence of Didemnun vexillum (an invasive non-native Carpet Sea Squirt) around North West Anglesey after March 2018, when Storm Emma destroyed Holyhead marina. Live Didemnum vexillum, previously found to be established on the marina structures and nearby boat hulls and moorings, was presumed to be distributed on marina debris around NW Anglesey. Shore and diving surveys were conducted in October 2018 in the marina area and where the bulk of floating material was washed ashore on the NW of Anglesey coast early in March 2018. D vexillum was only located on the various marina structures that survived the storm and on boat hulls and moorings in the areas where it had been found on previous surveys. This dataset details the presence and absence of Didemnun vexillum (an invasive non-native Carpet Sea Squirt) around North West Anglesey after March 2018, when Storm Emma destroyed Holyhead marina. Live Didemnum vexillum, previously found to be established on the marina structures and nearby boat hulls and moorings, was presumed to be distributed on marina debris around NW Anglesey. Shore and diving surveys were conducted in October 2018 in the marina area and where the bulk of floating material was washed ashore on the NW of Anglesey coast early in March 2018. D vexillum was only located on the various marina structures that survived the storm and on boat hulls and moorings in the areas where it had been found on previous surveys. 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 Cloud Base Productions Ltd. Cloud Base Productions Ltd., Tan Hwfa, Llanllechid, Bangor, LL57 3LA rohan@cloudbasepro.co.uk www.cloudbasepro.co.uk 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 Invasive Non-Native Species (INNS) colonial sea squirt invasive species (alien species) Didemnum vexillum marinas and marine docks Holyhead NRW Thesaurus 2026-03-02 geonetwork.thesaurus.local.theme.converted_nrw-keywords Man-made structures Habitat characterisation SeaDataNet Parameter Discovery Vocabulary 2024-06-19 geonetwork.thesaurus.external.theme.rdf+xml IPSV Subjects List 2020-11-18 geonetwork.thesaurus.external.theme.subjects NRW SMNR Keywords 2024-06-26 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. Attribution statement: Contains Natural Resources Wales information © Natural Resources Wales and Database Right. All rights Reserved. English biota SeaVoX Vertical Co-ordinate Coverages 2021-01-06 benthic boundary layer Wales (WLS) -4.75368 -4.32871 53.1582 53.41515 2018-10-09 2018-10-26 Holt, R.H.F. 2018. Didemnum vexillum: survey of distribution and extent in Holyhead Harbour after storm Emma, October 2018. NRW Evidence report no. 306. Database [A] Digital versions of the contract report: Microsoft Word document; and an Adobe Portable Document Format version. [B] Excel spreadsheets with species presence absence data. [C] Photographs of habitats and species [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 areas were investigated on foot with particular care taken to inspect marina debris, underboulders, overhangs and shaded vertical surfaces where didemnids are most likely to occur. Subtidal structures and natural features investigated by diving, concentrating on the types of habitat where D vexillum had been found previously: vertical and overhanging shaded surfaces of floating pontoons, boats and mooring buoys and chains. Fixed man-made and natural habitats where didemnids are known to occur were also investigated including harbour walls, jetty pilings, rip-rap and naturally occurring boulders. The intertidal survey covered 9 areas on the NW coast of Anglesey plus Porth y Felin and Scimitar beach in Holyhead New Harbour. Diving surveys were carried out on 58 locations in the New and Old Harbour areas to include the remains of the marina, boats and moorings in the New Harbour and structures, walls, pilings and natural rocky features in the New and Old Harbours. Presence / Absence data was collected for any occurrence of D vexillum with notes made of approximate abundance and the notable presence of any other non-native species. Intertidal areas were investigated on foot with particular care taken to inspect marina debris, underboulders, overhangs and shaded vertical surfaces where didemnids are most likely to occur. Subtidal structures and natural features investigated by diving, concentrating on the types of habitat where D vexillum had been found previously: vertical and overhanging shaded surfaces of floating pontoons, boats and mooring buoys and chains. Fixed man-made and natural habitats where didemnids are known to occur were also investigated including harbour walls, jetty pilings, rip-rap and naturally occurring boulders. The intertidal survey covered 9 areas on the NW coast of Anglesey plus Porth y Felin and Scimitar beach in Holyhead New Harbour. Diving surveys were carried out on 58 locations in the New and Old Harbour areas to include the remains of the marina, boats and moorings in the New Harbour and structures, walls, pilings and natural rocky features in the New and Old Harbours. Presence / Absence data was collected for any occurrence of D vexillum with notes made of approximate abundance and the notable presence of any other non-native species.