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unrestricted use, copyright acknowledgement - To use the data, permission must be requested from data owners,Welsh Fishermen’s Association - Cymdeithas Pysgotwyr Cymru (WFA-CPC). No data or information from these archived datasets may be reproduced, transmitted or copied without the permission of the owners, the Welsh Fishermen’s Association - Cymdeithas Pysgotwyr Cymru (WFA-CPC).

Envision was contracted to undertake the survey on behalf of Welsh Fishermen’s Association (WFA-CFC). This resource is part of a multidisciplinary series 2019-2021 WFA-CPC EMFF PROTECTING OUR SEAS PROJECT (see https://portal.medin.org.uk/portal/start.php#details?tpc=010_d8f12e7ea0689c2c570d15b48a283367). Broad-scale acoustic data was collected using the interferometric swath bathymetric system (GeoSwath Plus) and an Acoustic Ground Discrimination System (RoxAnn™ AGDS). A series of survey lines were planned to incorporate four survey blocks, traversing parallel survey lines throughout each block. The line spacing was 50m and infill line spacing was 25m, with infill used in shallow areas where needed. Survey lines were run to a navigable safe depth and no shallower, at approx. 4knts. At all 12 secondary survey areas, high frequency (1 MHz) sidescan sonar data were collected by deploying the tow fish from the stern of the vessel and traversing parallel lines at a constant speed. The underwater sonar camera system (ARIS 3000) was then towed over the same areas as the vessel drifted with the current/wind at slack tides. Start, end and a continuous log of GPS positions were recorded. Keywords: Welsh Fishermen’s Association - Cymdeithas Pysgotwyr Cymru (WFA-CPC), Severn Esturary/Môr Hafren SAC, Benthic and Geophysical surveys, Sabellaria alveolata, Reef, biogenic, acoustic data, interferometric swath bathymetric system, bathymetry, sidescan sonar, high frequency sidescan sonar, Acoustic Ground Discrimination System (RoxAnn™ AGDS), acoustic imagery data, Acoustic Resonance Inspection System (ARIS Explorer 3000) camera, acoustic reflectance, variable ground, feature identification, Trident SeaStar, fishing activity data.

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