Fladen experimental fishing impact recovery data - Sediment profile imagery
Biological (presence of infauna, tubes) and physical (apparent redox potential discontinuity (aRPD) layer, penetration depth, surface roughness) parameters measured, and a Benthic Habitat Quality Index assessment, from sediment profile images of the seabed with associated station information. The sediment profile images were acquired from a self-contained photographic system at sampling stations located within six experimental boxes (three treatments and three control) during a fishing impact recovery survey within the Fladen Grounds. Data were collected at three time points (before impact (time 0), immediately after impact (time 1) and 8 months after impact (time 2) during two research surveys on the RV Cefas Endeavour in April 2015 and November 2015. 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.
RV Cefas Endeavour Staff / Silburn, Briony / Brown, Louise
Benthos / Sediment / Seabed photography
RV Cefas Endeavour Staff, Silburn & Brown (2019). Fladen experimental fishing impact recovery data - Sediment profile imagery. Cefas, UK. V1. doi https://doi.org/10.14466/CefasDataHub.86