Multipurpose use of side-scan sonar technology for fisheries science

Abstract

This study illustrates some potential applications of side-scan sonar to explain issues related to fisheries science. Side-scan sonar enabled identification of the footprint of different trawl types. It showed that a twin trawl sweeps a 30% greater area than a traditional trawl and that a semipelagic trawl door has more limited impact than a traditional bottom otter trawl. The side-scan sonar enabled detection and characterization of the interaction of trawl gear with the seafloor. It demonstrated the cod end is floating above the sea bottom during the tow, while the doors and clumps, sweeps and bridles have the most damaging effect on the seafloor. Side-scan sonar was used to assess the interaction between active and passive gear and between trawls and pipelines. It has been able to detect illegal fishing activity in marine protected areas and has been a valuable tool to resolve disputes between different sectors. Side-scan sonar was finally tested as a suitable tool for fish school detection and counting. Side-scan sonar emerged as a flexible tool to tackle rapidly a number of issues related to fishing impact, technology, and biology.