54b0db41aa9b52bd7e632c85958a6e3f English dataset Data Archive for Seabed Species and Habitats (DASSH) Data Manager 01752 633102 01752 633291 Marine Biological Association of the UK, The Laboratory, Citadel Hill Plymouth PL1 2PB dassh.enquiries@mba.ac.uk pointOfContact 2024-12-02 MEDIN Discovery metadata standard 2.3.8 urn:ogc:def:crs:EPSG::0 urn:ogc:def:crs:EPSG::4326 1999-2001 University Marine Biological Station Millport (UMBSM) Clyde Sea Rapid Methodologies Survey 1999-2001 University Marine Biological Station Millport (UMBSM) Study Contract Clyde Sea Rapid Methodologies Survey EC Study Contract 98/017 2001-06-01 publication 2020-01-14 creation 2020-01-14 revision DASSH-113 http://www.dassh.ac.uk/datasets This dataset consists of pooled samples from the Clyde Sea portion of EC Study Contract 98/017. A study was carried out which investigated the effectiveness of rapid methodologies in quantifying the effects which otter trawls have on the marine environment. The research evaluates and compares rapid methodologies as alternatives to traditional (slow and costly) methods. Investigations were carried out on Norway lobster (Nephrops norvegicus) grounds in the Clyde Sea area, in Scotland, and a 'multi-species' fishery ground in the Aegean (Crete). Sample sites were selected to reflect a range of trawl impacts on the benthic environment. Scottish sites which were investigated covered three levels of fishing intensity; heavy, moderate and light. Aegean sites covered a succession of trawling intensities. An experimentally manipulated site was created off the island of Crete in an area previously unfished, to compare trawl impact. There were four categories of rapid methodologies which were evaluated. The categories include; acoustic, visual, biological and sedimentological. Acoustic methods of evaluating trawl impact included bottom discriminating sonar (RoxAnn(trademark)) and sidescan sonar. Trawling effects were detected by the latter. Visual methods included the use of underwater television, which was either deployed on a tow-sledge or on a remote operated vehicle (ROV). The study found that underwater television produced a better rapid assessment on the ecological impacts of trawling than other methodologies evaluated in this study. Biological methods investigated the tissue damage of selected species (molluscs, crustaceans, echinoderms), population density and the functional group composition of sampled communities. Benthic megafauna (mostly epifauna) was collected from sites of varying trawling intensity. A 2-metre beam trawl was used for sites in the Clyde Sea area while an Agassiz trawl was used for Aegean sites. Sedimentological methods of assessment included granulometry (geotechnical tests and sediment profile imagery (SPI). SPI provided a relatively rapid evaluation of trawled and untrawled site comparisons. The study provides a recommendation list of techniques which are suitable for rapid assessment of otter trawl impacts on soft substrata. The operational constraints and cost effectiveness of various methodologies are discussed. Philip Smith University Marine Biological Station (UMBS), Millport Millport KA28 0EG philip.smith@millport.gla.ac.uk originator Data Archive for Seabed Species and Habitats (DASSH) Data Manager 01752 633102 01752 633291 Marine Biological Association of the UK, The Laboratory, Citadel Hill Plymouth PL1 2PB dassh.enquiries@mba.ac.uk custodian notPlanned Delimited Marine Environmental Data and Information Network Species distribution GEMET - INSPIRE themes, version 1.0 2008-01-06 revision Fish abundance in water bodies Fishing by-catch SeaDataNet P021 parameter discovery vocabulary 2009-11-16 revision Open Access; Open Government Licence otherRestrictions Open Access English biota Charting Progress 2 Sea Areas 2009-06-18 creation Irish Sea International Hydrographic Bureau, Limits of Oceans and Seas 1954-01-01 creation Irish Sea and St. George's Channel SeaDataNet vertical extent keywords 2010-01-01 revision benthic boundary layer SeaDataNet vertical extent keywords 2010-01-01 revision infralittoral SeaDataNet vertical extent keywords 2010-01-01 revision littoral SeaDataNet vertical extent keywords 2010-01-01 revision soil and sediment boundary layer -5.1667 -4.8333 55.5833 56.0000 1999-04-01 2001-06-01 Data Archive for Seabed Species and Habitats (DASSH) Data Manager 01752 633102 01752 633291 Marine Biological Association of the UK, The Laboratory, Citadel Hill Plymouth PL1 2PB dassh.enquiries@mba.ac.uk distributor http://doi.org/10.17031/tpgjrv DOI link A link to the web service or dataset http://www.dassh.ac.uk/ DASSH website A link to the general host site dataset This study was conducted by members of the University Marine Biological Station Millport (UMBSM), the Institute of Marine Biology of Crete (IMBC) and the Fisheries Research Services and was funded by the European Commission. The study does not necessarily reflect the view of the European Commission. The study project is in support of the Common Fisheries Policy. The study is aimed at establishing more reliable and rapid methods of assessing the impact which trawling has on fisheries. The research undertaken and the information gathered hopes to support a change to an ecosystem based approach to fisheries management and lead to more efficient managing protocols on a pan European scale. Investigations were carried out on otter trawl fishery grounds as otter trawls are one of the most common types of fishery gears used within European waters. Despite being a major supplier of catch (Nephrops norvegicus in Scotland; multi-species fishery in the Aegean) in Europe, it is one of the least studied fishing gears in terms of ecological impact. The Clyde Sea area constitutes a major Norway lobster (Nephrops norvegicus) fishery and is heavily trawled. The Norway lobster stocks are one of the most valuable shellfish resources in the North East Atlantic, with landings of around 60,000 tonnes. Scottish landings alone reached 22,500 tonnes with a value of over 45M GBP, in 1995. Recently, landing values have encroached up to 60M GBP. Annual Clyde Sea landings reach 4000 tonnes alone. Otter trawls used may have single rigs, with a mesh size of 70 mm, or twin rigs which have a mesh size of 80 mm. In the Mediterranean, where a basic type of demersal trawl is used on all grounds, mesh size is set at 40 mm. Demersal trawl landings reached 19% of the total landings (tonnage), however it represented over 30% of the market value (24M EURO). Study site selection in the Clyde Sea area was based upon local knowledge of Nephrops fisheries and data recorded by another EC Study Project which mapped the distribution of otter trawl fishing effort. In the EC Study project, 20% of the otter trawl fishing fleet had been fitted with positional logging devices. This data was used to establish six suitable study sites (two within each trawl intensity category) for this study. Each site was approximately 1NM squared in area. Sites were established around the isle of Bute and Cumbrae and the Loch Long area. Two areas were selected for study within the Aegean to enable comparisons of investigative methodologies. Both study areas were situated around Iraklion Bay, Crete (Southern Aegean). This area was selected due to its know, and previously studied commercial trawl lanes. Trawling areas were distinguishable and a towed underwater video-sledge was used for aiding in the allocation of study sites. Within this area, a sampling site was allocated in a trawling lane (200 m depth) and two control sites were established at the north and south of the trawling lane. The second research area within the Aegean was situated at Gouves, a shallower trawling ground (60-120m depth). Two small study sites were established at Gouves. Commercial trawling is present within the area, however the fishing activity is less known. An experimentally fished lane and an adjacent control lane were established. Both lanes were situated in commercial restricted areas, protected from trawling by reefs. A 2m beam trawl was selected over a 2m Agassiz trawl for the sampling of megafauna within the Clyde Sea area, due to sedimentological reasons. Both gear types were used in the Aegean. In the Clyde Sea area, a bottom-discriminating sonar survey was carried out at each study site using a Simrad 38 kHz single beam sonar transducer, Simrad EK500 scientific echo-sounder and a RoxAnn (trade mark) unit. The transducer was deployed at a depth of 4 m and towed at a speed of 8 knots. Surface-modeling software (applied to substratum roughness and hardness data) was used to generate false colour composite images of the sea bed at each site. The images enabled similar sediment properties of the sea bed to be distinguished. In the Aegean, a similar bottom-discriminating sonar unit was used (with 120 kHz frequency) to map study sites in both research areas. Underwater television was used in conjunction with sonar and trawl sampling. Towed video sledge methods were used to survey transects while ROV methods were used for spot surveys. Both underwater television methods were used to survey the Clyde Sea sites. The towed video sledge method was adopted in the Aegean. Two sidescan sonar surveys were carried out to assess the sediment of study areas in the Clyde sea. Both surveys were performed using a sonar imaging unit. This unit consisted of a Geoacoustics 159D Sidescan towfish and transceiver (geoacoustics 5210) and an Isis PC-based recording package. The towfish was deployed and reached a depth of 6m above the sea bed. The sidescan sonar operated at a frequency of 100kHz and had a swathe of 240m. The first survey undertook a side scan over the study area in a series of parallel tracks, creating a mosaic image of the sea bed. The second survey followed a grid design which allowed single images of trawl marks to be obtained and analysed. These individual frames of the sea bed were used to establish the density and the orientation of trawl marks which were apparent. Similar surveys were performed in the Aegean. Five replicate tows (15 minutes) were performed at each Clyde Sea site in order to sample the epibenthic megafauna. The 2 m beam trawl (paired) was rigged with 20mm stretched mesh net and lacked tickler chains. Each sample was kept separately, weighed and processed. The paired samples were separated. One trawled sample was sorted and organisms were identified to species level where possible. The second trawled sample from the pair was used to enhance the sample size of selected taxa on which damage assessments and investigations could be performed. In the Aegean, trawls were carried out for 30 minutes and 15 minutes at Iraklion Bay (Dia Island) and Gouves respectively. The Agassiz trawl catch (cod-end) was emptied into a basin, provided with a station ID number, photographed and roughly sorted into phylum groups. Catch was identified, enumerated, weighed and discarded when possible. Morphometric data of certain species was also attained. The rest of the fauna was preserved in 10 percent formalin for laboratory processing. A quantitative assessment of damage load of fauna was performed to assess the trawling impact at different sites. The common starfish (Asterias rubens) and two large gastropods, the common whelk (Buccinum undatum) and the red whelk (Neptunea antigua) were used for damage load assessments in the Clyde sea area. Damage load assessments of starfish included counts of: number of complete arms, number of regenerating arms, number of fresh autonomy wounds, number of healed autonomy wounds and the number of intact arms displaying previous damage. The shell of whelks was assessed to establish damage load of the gastropods. Damage was categorised as recent (damage not yet repaired), past (scar) and sub-categorised as light (small chips or scars on shell of a few millimeters) and severe (substantial breakages or larger scars). In the Aegean, Agassiz trawl catch provided small, unsuitable fauna for damage load assessments. Otter trawl catches were used instead. Echinoderm groups (Ophiuroid, Asteroid, Echinoid, Crinoid, Holothuroid) were assessed for damage and were evaluated immediately on deck. Damage assessment recognised broken or missing arms/spines/cirri or scrapes as damage. Three or more arms lost, test erupted, more than 50% of arms badly damaged or missing and body rupture were designated as severely damaged categories. The variability of fauna damaged in trawling grounds and their population densities were assessed. Towed fishing gear has an effect on the physical properties of sediment. Undisturbed core samples from each survey site in the Clyde sea were obtained quarterly. Two coring devices were used: Connelly 4-channel multi corer and a modified Craib corer. Geotechnical testing of samples was conducted by the Biosedimentology Unit of the Institute of Biomedical and Life Sciences of Glasgow University (BU-GU). Granulometric analysis of sediment samples were performed by the Fisheries Research Services (Marine Laboratory, Aberdeen (MLA)). A 0.1 m squared Smith-McIntyre grab was used in the Aegean to obtain sediment samples. A sub-sample of the grab was taken using a 5.5 cm diameter core tube to 5 cm depth. A sediment particle size analysis was performed following a modified method. Sediment profile imagery was performed in the upper 20 cm of the sediment.