Fladen experimental fishing impact recovery data - Seabed imagery analysis

notPlanned

Two camera sledge tows were positioned diagonally across each of the six experimental boxes. The camera sledge system comprised a Kongsberg 208 video camera with still image capability. Illumination was provided by four high intensity LED lights and a dedicated flash unit. The camera was orientated to provide a forward oblique view of the seabed and was fitted with a four-spot (red) laser-scaling device which projected the corners of a 17cm x 17cm square along the axis of the lens onto the seabed. Set-up and operation followed the MESH ‘Recommended Operating Guidelines (ROG) for underwater video and photographic imaging techniques. A video overlay was used to provide station metadata, time and position (of the GPS antenna) in the recorded video image. The camera sledge was towed at ~ 0.3 knots and still images were captured at one-minute intervals. The position of the sledge was derived from a High Precision Acoustic Positioning (HiPAP) beacon which was continuously logging at 10 second intervals throughout the tow. Video and still photographs were analysed to identify the broadscale habitats within the video record, to provide abundance and the Marine Nature Conservation Review (MNCR) Abundance Scales (SACFOR) data on the species present and to quantify the number of nephrops burrows present. Identification of taxa was limited to a level that could be confidently achieved from the available image. Quality was managed through a quality control system in place by the contracting laboratory undertaking the seabed imagery processing and by Cefas.