An estimate of mesoscale biomass of Antarctic krill (Euphausia superba) in the East Antarctic

In January 2019 a mesoscale acoustic-trawl survey (Area = 251,767.5 km²) was carried out in the East Antarctic to estimate the biomass of Antarctic krill (Euphausia superba). The survey was run from the Australian Research Vessel R/V Investigator operating an EK60 scientific echosounder and RMT8+1 net. Krill areal density biomass was calculated using the swarms-based technique which was in turn used to estimate mean areal biomass density of 18.3 gm^-2 and biomass 4.6 million tonnes, with CV = 11.1 % . We examined the effect on biomass estimates surveying during day and night and found negligible differences in estimated biomass. As expected, estimated CV increased due to smaller sample sizes when the data were split into day and night.