Trawl marks, iceberg ploughmarks and possible whale-feeding marks, Barents Sea

Abstract

Humans, other animals and geological processes leave their imprint on the seafloor. The interpretation of such features may be challenging. Very-high-resolution synthetic aperture sonar (SAS) data and seabed photographs (TFish) have recently been acquired from the Barents Sea using the HiSAS 1030 and TFish systems on the autonomous underwater vehicle (AUV) HUGIN HUS. These data demonstrate the clear morphological distinction between iceberg ploughmarks and trawl marks produced during fishing, and also enable the interpretation of small, irregular depressions as whale-feeding marks. A 13 km2 area was imaged with a very-high-resolution SAS deployed from an AUV (Fig. 1a–c), nested within 175 km2 of conventional hull-mounted multibeam data (Fig. 1d) on the Loppa High, SW Barents Sea (Fig. 1h). Water depths here range from 420 to 440 m. SAS data were processed to give imagery with a resolution of 7×7 cm and bathymetric grids at 20×20 cm. TFish photographs (resolution 5×5 mm/pixel) were also acquired from the AUV from selected sites. Fig. 1. Multibeam bathymetry, SAS imagery and micro-bathymetry, and seafloor photographs of trawl marks, possible whale-feeding marks and iceberg ploughmarks. ( a ) SAS imagery of trawl marks and whale marks. Acquisition system Kongsberg HiSAS 1030 (wideband SAS sonar, frequency 70–100 kHz). ( b ) SAS micro-bathymetry …