Fladen experimental fishing impact recovery data - Sediment profile imagery

notPlanned

The camera system is a self-contained photographic system used for collecting *in-situ* images of the sediment/water interface. The system comprises a Nikon D100 digital camera, 35 mm lens, water filled prism, a self- contained strobe light, adjustable penetration stops, adjustable fall rate, and a stainless-steel construction frame. The frame also possesses mud doors to facilitate the use of the camera in low shear-strength muds. The supporting frame lands on the seabed first, leaving the area directly under the prism undisturbed. As the winch wire is slackened, the prism cradle descends toward the seabed at a controlled rate, and as the wedge-shaped prism enters the muddy bottom, it is driven into the sediment by its weight. The piston ensures that the prism enters the bottom slowly and does not disturb the sediment - water interface. On impact with the seabed, a trigger activates a time delay on the camera shutter release and two photographs are taken. Once the images are acquired, tension on the winch wire raises the prism cradle to the up position, a wiper blade cleans off the face plate, the strobe is recharged and the system can be lowered for another image. The camera system was ‘hopped’ over the seabed providing a series of images along a transect (5 hops spaced 5 m apart resulting in 10 images per station) at a subset of three stations within each experimental box. From each of the three stations within the experimental boxes, five images (one from each hop) were analysed to determine penetration depth, surface roughness and aRPD, using the well-established semi-automated Java macro within *ImageJ* (Version 1.46r). Ten percent of the images were processed by two analysts to ensure quality. The average aRPD, penetration depth and surface roughness was then calculated for each station within an experimental box.