69da2e3f24741fdba75e2173bcb081b5 English dataset DASSH, The Archive for Marine Species and Habitat Data 01752 426237 dassh.enquiries@mba.ac.uk pointOfContact 2025-12-16 MEDIN 3.1.2 EPSG Geodetic Parameter Registry 2021-01-06 revision WGS 84 1999 UMBSM/ IUEM/ ICRAM/ MLA Clyde Sea Toothed Dredge Impact Survey - Grab and Suction Sampling 1999 University Marine Biological Station Millport (UMBSM) Study Contract Clyde Sea Toothed Dredge Survey 1999 UMBSM/ IUEM/ ICRAM/ MLA Clyde Sea Toothed Dredge Survey 2023-06-22 publication 2023-06-22 revision 1999-06-07 creation DASSH-116 https://www.dassh.ac.uk 1999 University Marine Biological Station, Millport, Marine observatory of the European University Institute of the Sea, ICRAM, Chioggia, Fisheries Research Services, Aberdeen Marine Laboratory Clyde Sea Toothed Dredge Survey An 18-month REEFS research project was undertaken to investigate the three main types of toothed dredge gear used for scallop (Pecten, Aequipecten spp.) fishing in Europe. Field investigations were carried out to assess the ecological impact of scallop dredging and experimental fishing studies were performed. The three scallop grounds which were investigated during the study were: Northern Adriatic (Italy); the Bay of Brest (North-Western France); and the Clyde Sea area (West coast of Scotland), which were paired sites. The study compared the effects of different types of toothed dredges on scallop grounds. Rapido trawls were used on the sandy bottom encountered in the Adriatic scallop fishing grounds. Brenton dredges were used in the French scallop grounds and Scottish grounds used the Newhaven trawl. Both scallop grounds were maerl based. The lighter weight rapido trawl penetrates surface sediment to 2cm to dislodge scallops and flat fish in the surface of the sea bed. Both the Brenton and Newhaven trawls penetrated the sediment surface down to 10cm. They are designed to be heavier to cope with more difficult fishing grounds. Toothed dredging field manipulation experiments identified the major ecological impacts of scallop fishing. The study established that toothed dredging had an impact on the sediment surface physical features, re-suspended silt fractions and disrupted sessile epifauna and habitat characterization. Dredging tracks were littered with dead or damaged organisms which attracted scavengers. Dredging tracks can be visible for a period of months to years. Areas with highly mobile sediment characterization were able to erase the effects of dredging faster than areas of sheltered mud or maerl. Experimental impact assessments were performed to determine the effects of dredging on surface living and sessile organisms. The experiments were conducted on sites in the Adriatic, France, and Scotland where commercial fishing was not possible. Bottom samples (up to 60cm below the sea bed) were taken via suction-lift techniques. Water lifts were used in the Adriatic site while air lifts were used in the French and Scottish sites. Sampling was also conducted using grabs. The investigations revealed that organisms living in the surface layer of the sea bed are disturbed by the process of dredging, however organisms are small enough to deter damage and survive. Deep burrowing organisms, large and long-lived species, are protected from toothed dredges (as adults). Large, sessile epifauna are the organisms which suffer the most impact of dredging and form the bulk of by-catch. Damaged organisms and discards of dredging are exploited by scavenging organisms. Toothed dredges are renowned to be the most environmentally damaging of the fishing gear which is towed in European waters. The project has established that toothed dredges affect the same sea bed area differently and therefore impacts the ecology of the substrata differently. DASSH, The Archive for Marine Species and Habitat Data Data Manager 01752 426237 dassh.enquiries@mba.ac.uk owner DASSH, The Archive for Marine Species and Habitat Data Data Manager 01752 426237 dassh.enquiries@mba.ac.uk custodian Philip Smith University Marine Biological Station (UMBS), Millport philip.smith@millport.gla.ac.uk originator DASSH, The Archive for Marine Species and Habitat Data Data Manager 01752 426237 dassh.enquiries@mba.ac.uk distributor notPlanned Marine Environmental Data and Information Network MEDIN metadata record availability 2026-01-05 revision Habitats and biotopes Land cover Oceanographic geographical features Species distribution GEMET - INSPIRE themes, version 1.0 2021-09-28 revision Fauna abundance per unit area of the bed Fishing by-catch Habitat characterisation Seabed photography Sediment resuspension SeaDataNet Parameter Discovery Vocabulary 2021-09-28 revision otherRestrictions Open access otherRestrictions Open Government Licence - https://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/ English 8-bit variable size UCS Transfer Format, based on ISO/IEC 10646 biota economy environment geoscientificInformation oceans -5.3641 -4.9658 55.7178 56.0613 Charting Progress 2 Sea Areas 2021-01-06 creation Minches and Western Scotland ICES Rectangles 2021-01-06 creation 40E4 ICES Statistical Areas 2021-01-06 creation VIa 1999-06-07 1999-06-07 SeaVoX Vertical Co-ordinate Coverages 2021-01-06 revision benthic boundary layer Delimited https://doi.org/10.17031/648713bbb256d.1 DOI link A link to the web service or dataset download 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 MEDIN data guideline for sediment sampling by grab or core for benthos 2011-01-28 publication true The research was carried out by members of the University Marine Biological Station Millport (UMBSM), the Institut Universitaire Europeen de la Mer (IUEM), the Instituto Centrale per la Ricerca scientifica e technologica Applicata al Mare (ICRAM) and the Fisheries Research Services, Marine Laboratory Aberdeen (MLA). The study has been carried out with the financial assistance of the European Commission. The report does not necessarily reflect the views of the European Commission. The study project is in support of the Common Fisheries Policy. The research programme was designated the title: "Research into the Environmental Effects of Fishing for Scallops". The acronym REEFS was assigned during a meeting of the partner institutions. The main purpose of the programme is to establish detailed comparative information on the effects of various fishing gear on valuable shared maritime resources, which can then be used to efficiently co-ordinate the management of global fisheries. All study sites were position fixed using DGPS. A side scan sonar (Model 260TH surface control unit, Model 272TD 'tow fish') was also used at the study area in the Adriatic. The sidescan sonar was used to accurately map the wreckage of the 'Quintino Sella' (unfished control site) and to locate rapido trawl tracks on the adjacent scallop fishing ground. Divers were used to establish the control site plot. In the french (Kongsberg-Simrad Model OE1360) and Italian (Telesub Laterna, Pozano Magra, Model PN 302.014) study sites, underwater television cameras (UWTV) were used to assess the epibenthic ecology and sea bed conditions of both the control and test sites. These methods were developed at UMBSM and adapted to film scallop dredges used in France and Italy. Within the Clyde Sea area, study sites were chosen that had previously been surveyed using RoxAnn (trade mark)(ROV) and divers. In addition, stills cameras (Nikonos V) were used to record the changes of benthic conditions. Experimental sites during the project were chosen as they were not commercially fished for scallops. Study sites were not commercially fished due to: its proximity to a wreck (Italy); the presence of an underwater communication cable (Scotland); and an agreement by fishers (France). At each site, between four and seven replicate ca 15 minute tows were performed. Gear rigging and towing speed reflected the common practices identified within each local fishing ground (5 knots in Italy; 2 knots in France and Scotland). The catch from each tow was hauled on-board and emptied onto the deck. The catch was sorted and collated into phylum categories and wet weighed. Pecten jacobaenus (Italy), P. maximus (France and Scotland) and Aequipecten opercularis were kept separate. The scallops were identified to species level, counted and assessed for dredge damage. Small macrobenthos were weighed and identified. Unidentifiable organisms were preserved (8% borax-buffered formalin in sea water) or frozen for later examination. Benthos suction samples (4mm mesh sieve) were obtained at all sites. Trials by UMBSM established the use of 0.5metre squared steel quadrats with 30 cm high walls as sufficient for suction sampling. Three replicate suction samples were obtained at 0-10, 10-30 and 30+ cm depth intervals, before and after experimental fishing investigations. In each region, investigations into deep-burrowing juvenile success and settlement were performed with the use of a 0.1metre squared grab sampler. Juvenile members were located in the surface layers of the sediment. Grabs were weighted with 30 kg of lead to ensure penetration to 8-10 cm of sediment. Samples were passed through a 1mm mesh sieve on deck and preserved in 8% borax-buffered solution of formalin seawater. Sorting of organisms preceded. The report describes each particular tow, suction and sampling methods which were adopted at each study site in full. Two study grounds (maerl) were established in the Clyde Sea area (10-12m below Chart Datum (CD)), which supported both UK commercial scallop species P. maximus and A. opercularis. Site 1, Stravanan Bay, has had a 40 year scallop fishing history in comparison to site 2 which had never been fished (trawling-prohibited area since 1968). Pre-fishing surveys were performed at each site during April-May 1999. The initial site surveys established that grounds were suitable for research trawling by locating obstructive debris. The presence of previous dredge tracks were recorded by divers and assessments of scallop densities, maerl coverage and conspecific species presence and abundance were performed using 1 meter squared quadrats. Each survey site was marked with a large floating buoy. Two plots (test and control) at site 1 were established within a 50x50 m square situated around the buoy marker. Test and control plots were situated either side of the marker. Sediment samples at site 1 were taken 2 days prior to fishing experiments. Fifteen Van Veen grab samples were also taken within the Plot area (8 in the control plot; 7 in the test plot). At site 2, three Newhaven scallop dredges were towed at a speed of 2-3.5 km per hour as is reflected by commercial scallop fishing vessels. The dredging of experimental plots was performed via RV Aora (UMBSM) and lasted for 15 minutes on each ground (total of four on each ground). Dredges were performed as close to buoy markers as possible. Catches from each tow were analysed and UWTV video footage (taken prior to trawl at site 1) was compared with footage obtained in Italy and France. Once dredging experiments were performed, post-fishing surveys of site 1 were carried out. The impacted area and damage caused (including fauna impacts) by dredging was recorded and photographed by divers within 1 hour of the trawl ceasing. Fishing gear efficiency was assessed by observing scallops left on the sea bed and compared to those which had been caught. Sediment samples were collected again two days after the fishing experiments. This data has been reviewed against the DASSH Quality Assessment Criteria (http://doi.org/10.17031/64ccec5c7ba72) and been categorised as medium quality. 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.