DOI: 10.17031/64d1054758929
title: 2011 Scottish Natural Heritage (SNH) Scotland Didemnum vexillum records

description: The carpet sea squirt (Didemnum vexillum) is an invasive non-native species of colonial sea squirt that has recently been found in England, Ireland, Wales and at one location in the Clyde, on the west coast of Scotland. The potential ecological and economic impacts of this species are significant. A rapid response eradication programme in Holyhead Harbour is currently underway, showing signs of some success so far. However, it is not known how far this species has spread within the UK, and surveys are underway in England and Wales to determine its distribution. It is crucial to know as soon as possible how far it has spread, as
this information will determine what the appropriate response will be - if it is confined to only a few sites, it may be possible to attempt eradication. If it is already more widespread, then containment or control measures will be more appropriate.

No specific surveys targeting this species had previously been carried out in Scotland, so it was not known whether it was present just in the one marina in the Clyde or whether it was more widespread. This project involved a series of rapid assessment surveys of those marinas and harbours thought to be most likely at risk from establishment (e.g. those in the Clyde and on the west coast of Scotland) and will inform SNH’s policy for dealing with this species, as well as the wider UK policy for response.
description: Part of MSFD NNS baseline data collation project (Jan 2016). Subset of a dataset as we were only pulling out records for a selection of INNS. Contains records for Didemnum vexillum.

Original source: Beveridge, C., Cook, E.J., Brunner, L., MacLeod, A., Black, K. Brown, C. and Manson, F.J. (2011). Initial reponse to the invasive carpet sea squirt, Didemnum vexillum, in Scotland. Scottish Natural Heritage Commissioned Report No. 413 

PDF available from:
https://www.nature.scot/naturescot-commissioned-report-413-initial-response-invasive-carpet-sea-squirt-didemnum-vexillum 
https://www.nls.uk/e-monographs/2020/216548241.23.pdf


A methodical search of pontoon floats, anchor chains, pilings and any ropes or other items hanging into the water at each location was carried out for signs of D. vexillum by three researchers from the Scottish Association for Marine Science (SAMS). All the pontoons in the marina were inspected using viewing scopes and an underwater camera system operated from the pontoon walkway to collect video (Panasonic Optio W30 camera mounted on 2 m pole) and stills (Panasonic Optio W60 camera). Scrapers with fine mesh nets attached were also used to collect any suspect organisms for closer inspection. Surveys typically lasted between one and two hours depending on the size of the marina or harbour. The most effective survey method was for the group of researchers to stay together, with one person allocated to each of the side pontoons and the third person looking at the main walkway. This allowed instant confirmation by the survey team of any potential sightings of D. vexillum. Any additional non-native species found during the survey were recorded. Weather conditions and visibility of the water column was noted at each location. All the equipment was cleaned with sanitiser and the nets on each scraper changed between locations. Samples requiring verification were collected and preserved in alcohol for later inspection under a stereomicroscope.

If any sensitive species or biotope records are present within this dataset, they will have been removed. If you wish to request access to sensitive species records, please contact the metadata contact.  The UK Sensitive Species list has been agreed by UK statutory bodies and relevant experts. It can be viewed here https://docs.nbnatlas.org/sensitive-species-list/. Please note sensitive species lists can vary across the UK.