eacda9011880d084168cda10b679bdf5 English dataset (DASSH) Data Archive for Marine Species and Habitats 01752426237 dassh.enquiries@mba.ac.uk pointOfContact 2026-03-19 MEDIN 3.1.2 EPSG Geodetic Parameter Registry 2021-01-06 revision WGS 84 2023 - ongoing University of Plymouth (UoP) Isles of Scilly Trawling Impact BACI Survey 2026-03-19 publication DASSHSE00000062 A new byelaw is expected to be passed which will close 43% of the Isles of Scilly district to bottom-towed fishing gear. The byelaw will allow permits to be distributed to up to six fishing vessels to use otter trawl and scallop dredge. The grounds around Scilly have not been trawled for over a decade, however there is now renewed interest to fish the water around Scilly. This creates a unique opportunity to conduct a Before-After-Control-Impact study on the impacts of bottom-towed fishing gear. At each site 3x45 minute BRUV video and 2X100m TUV transects were completed. This project will consist of a baseline against which changes to habitat complexity and biodiversity of associated communities can be quantified following resumption of trawling. This survey was also replicated at sites which will fall under the byelaw extension, which will act as reference sites. Shion Reynell University of Plymouth shion.reynell@plymouth.ac.uk owner (DASSH) Data Archive for Marine Species and Habitats Data Manager 01752426237 dassh.enquiries@mba.ac.uk custodian Shion Reynell University of Plymouth shion.reynell@plymouth.ac.uk custodian Shion Reynell University of Plymouth shion.reynell@plymouth.ac.uk originator (DASSH) Data Archive for Marine Species and Habitats Data Manager 01752426237 dassh.enquiries@mba.ac.uk distributor notPlanned Marine Environmental Data and Information Network MEDIN metadata record availability 2026-03-19 revision NDGO0005 NDGO0005 2026-03-19 revision Species distribution GEMET - INSPIRE themes, version 1.0 2021-09-28 revision Fauna abundance per unit area of the bed SeaDataNet Parameter Discovery Vocabulary 2021-09-28 revision otherRestrictions Restricted access, please contact the metadata contact for further details otherRestrictions Not open access, please contact the metadata contact for further details 15 English 8-bit variable size UCS Transfer Format, based on ISO/IEC 10646 biota oceans -6.2094 -6.1181 49.8517 49.9823 SeaVox salt and freshwater body gazetteer 2021-01-06 creation Celtic Sea Charting Progress 2 Sea Areas 2021-01-06 creation Western Channel and Celtic Sea ICES Rectangles 2021-01-06 creation 28E3 ICES Statistical Areas 2021-01-06 creation VIIe 2023-05-01 2025-02-05 70.0000 90.0000 Delimited dataset 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 publication Baited Remote Underwater Video (BRUV) cameras were deployed to sample reef-associated nekton species and mobile benthic fauna. Six static frames (Greenaway Marine Ltd.) each housed a Panasonic HDC-SD60 full HD video camera and a battery-operated LED light mounted onto the frame (Figure 3). In the second survey, GoPro Hero 11 minis replaced the Panasonic cameras. Two 15kg weights were attached to the housing, and a 1m pole extending out from the centre of the cameras field of view held a 13cm wide wire cage bait box (Figure 3). These were baited with 100g fresh mackerel bait, which was replenished at the start of each deployment. At each site, three cameras were deployed approximately 100m away from each other, with a surface marker buoy attached. The cameras were deployed for a total of 45 minutes to allow for settling of sediment and 30 minutes of analysable footage to be captured. Quantitative data were extracted from the BRUV footage by counting the maximum number of individuals on screen (MaxN) for each taxon that is recorded during a 30-minute period. MaxN is considered a conservative estimate of relative abundance of mobile taxon attracted to the bait, as it decreases the chance of an individual being repeatedly recorded (Cappo et al., 2003). Organisms were identified to the highest taxonomic rank possible, and the counts expressed as MaxN (± SE) per taxa, per replicate. Replicates were averaged to increase precision and avoid pseudo-replication. To quantify changes in the abundance of sessile and sedentary benthic species, Towed Underwater Video (TUV) was used comprising a HD video camera mounted onto a flying array (Figure 4). In 2023 a Surveyor-HD-J12 colour zoom titanium camera was used. The use of TUV is particularly suitable for rapidly surveying large areas and is relatively low impact (Sheehan, Stevens and Attrill, 2010; Sheehan et al., 2016). This is necessary in an impact study, to avoid confounding assessments of change over time with impacts associated with the sampling method. At each site, two ~100m video transects were recorded in 2023 and 2024. At each site, the flying array would be dropped to depth. Once a suitable height off the seabed had been achieved, recording would be commenced and would continue for a period of 10 minutes equating to approximately 100m of seabed. Following completion of one tow, the array would remain at depth and the vessel would drift for a period of 10 minutes or a distance of 100m before recommencing recording for a second replicate. Due to the requirement for a drift speed below 0.5 knots per second, the vessel would be allowed to drift in any direction from the survey point according to the wind and tide.Analysis of the video transects are conducted in two stages: Species counts were made from each entire video transect by counting individuals that passed through the ‘gate’ formed by the two laser dots for infrequent organisms (all mobile taxa), and conspicuous sessile fauna. Taxa were recorded as density per m-2 for the species counts from video. Thirty frame grabs were extracted from each video transect (Sheehan et al., 2013; Stevens et al., 2014) and overlaid with a calibrated digital grid to quantify the encrusting, sessile species, and abundant, free-living fauna. The grid identifies the area of species to be enumerated. Analysts located the position of the grid in the HD video and use this in conjunction with the frame grab. This is to ensure that species identification is made to the highest resolution possible. A full species list is included in the appendices. Replicates were averaged to increase precision. Taxa were recorded as density (individuals per m2) for the species counts and either density or percentage cover (for ground cover and encrusting species) as appropriate for the frame grabs. For towed and baited video, all taxa present are identified and their abundance recorded. Identification was made to the highest taxonomic level deemed possible, but where appropriate and where inter-species distinctions are not possible from video analysis, some groupings were made. Data archived by DASSH but not disseminated.