Dredging impact measurement

Survey and monitoring to helped ensure aggregate producers could continue dredging the Kingmere MCZ

Any aggregate producers operating in the locality of Kingmere Marine Conservation Zone (MCZ) are required to monitor black bream nest viability and densities to ensure dredging causes no significant negative impacts.

Tarmac Marine Ltd and CEMEX UK Marine Ltd commissioned ABPmer to undertake an assessment of black bream (Spondyliosoma cantharus) nesting activity in survey areas both within, and in the vicinity of, the Kingmere MCZ to contribute to the annual monitoring requirements for the licences of Areas 453 and 488.

A geophysical survey was undertaken to record the multibeam backscatter data to provide an interpretation of the location and density of the bream nests.

ABPmer’s survey team used a survey vessel mobilised with a high-resolution Kongsberg 2040C multibeam echosounder interfaced with an Applanix PosMV inertial positioning system. Multibeam data was acquired in 9 survey areas in and around the Kingmere MCZ, during the peak breeding season, to identify and locate black bream nests.

The multibeam was processed for bathymetry and backscatter providing imagery at 10cm resolution enabling nest identification (which are of size approximately 1m in diameter) due to risen sediment around the nest and the cleared hard rock surface. The data was interpreted, and nests were classified in terms of density.

Post processing of the geophysical data was used to determine transects for subsequent drop-down video surveys. Three drop-down video surveys were undertaken between May and July to ground truth the multibeam results and to determine the seasonal extent of black bream spawning. For all surveys the ABPmer Drop-Down video (DDV) system, utilising a C-Tecnics CT3020 SLV video and digital stills camera, was used to capture high-resolution imagery. Three Go-Pro Hero 7 cameras were attached to the sides of the DDV frame to provide wider coverage of the seabed.

The video and photographic data from the surveys were assessed for the distribution and abundance of black bream nests and the presence of black bream eggs, where present, during the spawning season.

ABPmer has conducted the survey in 2019 and 2020.

Image © Andrew Pearson