Acoustic Monitoring of South Llyn (East of the Tudwels) and Subsequent Infauna Sampling
A side-scan sonar survey was carried out in Tremadog Bay following reports of possible scallop dredging within the Sea Fisheries Scallop Exclusion Zone. The acoustic survey was followed up by infaunal sampling to look at the effect of disturbance of the substrata within the area. The purpose of this data capture was to investigate reports of possible scallop dredging within the Exclusion Zone and its effects on biodiversity within the Special Area of Conservation (SAC) and Exclusion Zone. Confidence in this dataset is high. The side-scan data is processed to reduce errors (e.g. positional corrections).
- Identification
- Extent
- Distribution
- Quality
- Keywords
- Spatial Reference System
- Content
- Constraints
- Maintenance
- Metadata
Identification
- Identifier
- NRW_DS110872
- Alternative Title
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- Side-scan survey of South Llyn
- Metadata Language
- English
- Lineage
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Side scan-sonar data was captured from Countryside Council for Wales' (CCW) research vessel (R.V. Pedryn) using a CMAX CM800 side-scan sonar. Two areas were selected for infaunal sampling. A control site (with no dredge activity) and one area where there was evidence of recent dredge activity. Infaunal sampling was carried by divers using a 0.1 m2 quadrat. 5 Quadrats were randomly placed in the belly of a dredge scar and 5 within the control site. Surface material was collected by hand and a diver operated suction sampler was used to remove the sediment within the quadrat to a depth of 20cms using a 0.5mm filter mesh bag. Large cobbles within the sediment too big for sampler were removed by hand and placed in a large 0.5mm mesh sample bag along with the plastic bag containing surface cobbles and the suction sampler filter bag. A sediment sample was collected by the diver adjacent to the quadrat using a 1/2litre sealed plastic bucket for granulometry. The contents of the suction sample filter bag and cobbles from within the sediment were transferred to sample buckets on the surface and fixed in 20% formalin diluted with seawater. In addition one 2x2 m quadrat was photographed in 40 cm blocks at both the control site and within one dredge scar. Photos will be stitched together to create a photographic mosaic of the quadrat.
- Dataset Reference Date (Publication)
- 2009-08-31
Temporal Extent
- Begin date
- 2009-06-09
- End date
- 2009-08-31
- Topic category
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- Environment
- Biota
Extent
Extent
- Geographic Extent
- Irish Sea
- Geographic Extent
- GWYNEDD - GWYNEDD
))
Vertical Extent
- Medin Extent Keyword
-
benthic boundary layer
Vertical Extent
- Minimum value (metres)
- 0
- Maximum value (metres)
- -12
- Vertical CRS
Distribution
- Format Type and Description
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Documents
(
)
- Specification
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[A] Side-scan data mosaiced raster TIFF images [B] Video data as avi files [C] Dredge position and sample metadata in MapInfo TAB files [D] Images as JPGs and NEF raw files
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Documents
(
)
Quality
Data quality
- Quality Scope
- Dataset
- Conformity
- 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
- Explanation
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This dataset has not been assessed for conformance to the referenced INSPIRE regulation.
- Degree
- false
- Lineage
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Side scan-sonar data was captured from Countryside Council for Wales' (CCW) research vessel (R.V. Pedryn) using a CMAX CM800 side-scan sonar. Two areas were selected for infaunal sampling. A control site (with no dredge activity) and one area where there was evidence of recent dredge activity. Infaunal sampling was carried by divers using a 0.1 m2 quadrat. 5 Quadrats were randomly placed in the belly of a dredge scar and 5 within the control site. Surface material was collected by hand and a diver operated suction sampler was used to remove the sediment within the quadrat to a depth of 20cms using a 0.5mm filter mesh bag. Large cobbles within the sediment too big for sampler were removed by hand and placed in a large 0.5mm mesh sample bag along with the plastic bag containing surface cobbles and the suction sampler filter bag. A sediment sample was collected by the diver adjacent to the quadrat using a 1/2litre sealed plastic bucket for granulometry. The contents of the suction sample filter bag and cobbles from within the sediment were transferred to sample buckets on the surface and fixed in 20% formalin diluted with seawater. In addition one 2x2 m quadrat was photographed in 40 cm blocks at both the control site and within one dredge scar. Photos will be stitched together to create a photographic mosaic of the quadrat.
Keywords
Keywords
- Type
- Theme
Citation
- Date (Publication)
- 2008-06-01
Keywords
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NRW Thesaurus
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- acoustic remote sensing
- sediment epifauna
- sediment infauna
- sediment sample
- Infauna
- sidescan sonar
- acoustic observation (acoustic monitoring)
- benthic environment
- Tremadog Bay
- benthic communities
- surveillance
- marine sediments (coastal sediments) (intertidal sediments) (subtidal sediments)
- cockle dredging (hydraulic dredging)
- Type
- Theme
Citation
- Date (Publication)
- 2026-08-27
Keywords
Spatial Reference System
Content
Content Information
NRW Profile
Custom Elements
Constraints
Constraints
Limitations on Public Access and Use
- Restriction type
- Other restrictions
Access Constraints Directive
- Limitations
- no limitations
Access Constraints Text
- Other constraints
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There are no access restrictions to this data. NRW may release, publish or disseminate it freely.
Use Constraints
- Use constraints type
- Other restrictions
- Other constraints
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© CNC/NRW 2009 There are no use restrictions on this data. Recipients may re-use, reproduce, disseminate this data free of charge in any format or medium, provided they do so accurately, acknowledging both the source and NRW's copyright, and do not use it in a misleading context. It is the recipient's responsibility to ensure the data is fit for the intended purpose, that dissemination or publishing does not result in duplication, and that it is fairly interpreted. Advice on interpretation should be sought where required. To avoid re-using old data, users should periodically obtain the latest version from the original source. All intellectual property rights (including copyright and database rights) are owned by CCW, except video footage taken by Paul Kay. Applicants seeking to re-use this material should approach Paul Kay directly to obtain permission.
Metadata
Metadata
- File Identifier
- 4f4c4942-4343-5764-6473-313130383732 XML
- Metadata Language
- English
- Resource type
- Dataset
- Metadata Date
- 2026-09-28T14:06:52.698Z
- Metadata Standard Name
- NRW
- Metadata Standard Version
-
1.0