Antarctic krill (Euphausia superba) catch weight estimated with a trawl-mounted echosounder during fishing

This paper is the result of discussions during the EMM meeting held in 2015 (CCAMLR EMM report 2015, para 2.13-2.16). To calculate krill-catch (green weight) reported from the commercial fishery, current methods are based on data from codend volume, holding tank volume, data from flow meters, flow scales and meal conversions. To determine where the catch originates with high geographical resolution and precise estimations of green weight, we present results from an experiment employing an alternative method. We used an acoustic sensor with a transducer scanning across a section of the trawl fishing circle to collect data. As an interesting spin-off result, we observed that the krill were herded toward the center of the trawl, which is important knowledge in relation to the development of efficient trawl designs and to reduce energy use during fishing. The experiment also demonstrate that acoustically based catch weight monitoring has the potential to be used for reporting total krill catch weight in each trawl, potentially in real-time, and can be used across the krill fishing fleet. Similar methods could also be employed in similar types of trawl fisheries.