Underwater acoustics

In order to satisfy the expectations of scientists using the sonar system, efforts continued on the development of methods for acquiring, monitoring, processing and interpreting data from the water column and the seafloor.

R&D focuses on developing methods for analysing multifrequency seafloor reflectivity. This approach will be scaled up thanks to the platform of the vessel Thalassa, which has been modernized and fitted with 30 kHz, 90 kHz and 300 kHz multibeam echo sounders. The application of these methods to the mapping of benthic habitats for the CGFS and EVHOE cruises will continue with the fisheries community. A project to map cold-water coral habitats should get underway in 2019 in collaboration with biologists using calibrated reflectivity with AUV/HROV EM2040 and Thalassa EM304 for a cruise scheduled for 2020.


In the field of water-column analysis, a new milestone in the characterization of the biological layers of the Bay of Biscay using broadband acoustics will be achieved with the publication of Arthur Blanluet’s thesis. The same methods used to analyse EK80 broadband data will be implemented on the EK80 data acquired on the seafloor fluid discharges in the Bay of Biscay and off New Zealand during the QUOI cruise, the latter in collaboration with the National Institute of Water and Atmospheric Research (NIWA).

2019 will see the deployment of the Echosonde acoustic observatory off Le Croisic. Shore-based monitoring of data acquisition and the continuous analysis of flow data will get underway as part of a postgraduate position. As part of this initiative, and consistent with the collaborative DEEP project (Deep learning and artificial intelligence applied to the ecosystemic approach to fisheries), we will analyse the benefits of methods using artificial intelligence for these massive acoustic data sets which are acquired continuously.

The team has also been approached for a new project to map algae in the water column by acoustic means. Cruises have been scheduled for 2019 using the Haliotis and her EK60 and EK80 echo sounders (MARHALIO cruise). Through this project IFREMER hopes to perpetuate the exploratory developments of recent years and study the benefits that multifrequency echo sounders have brought to algae mapping.