The one nautical mile integrated Nautical Area Scattering Coefficient (NASC) values of four surveys in 48.1 fishing area were calculated using both the swarm-based and conventional grid-based acoustic data processing methods. All parameter settings were consistent with the reports of SG-ASAM-2017 except that the dB difference window of Sv_{120 kHz}-Sv_38kHz is set 0 to 20 dB. And the two groups of results were compared by correlation, linear regression analysis and nonparametric significant difference tests (Kruskal-Wallis tests) to examine the validation of the developed swarm-based method for Antarctic krill density estimation. The comparisons suggest that the calculated NASC values of swarm-based and grid-based method show non-significant difference and significant linear relationship for all the four surveys. Therefore, it is concluded that the krill density estimated by swarm-based and grid-based method could be of good agreement.

During the meeting, the subgroup suggested further analysis on swam-based approach and grid-based approach based on data in the paper. In accordance to the suggestions, further analyses were undertaken and the results were shown in Appendix A.

The distribution and abundance of krill aggregation inhabiting the Subarea 48.1, which includes the Elephant Island peripheries and the west and south of the South Shetland Island, were estimated using an acoustics survey. Acoustic data were collected with 38 and 120 kHz from April 13 to 24 in 2016 and 38 and 200 kHz from March 6 to 14 and 38 and 120 kHz on April 27 and May 5 in 2017. Krill were collected by the commercial middle trawl fishing vessel. The data were processed and analyzed following CCAMLR standard protocols using swarm integration (SHAPES module within that software for swarm identification) based on data from a transect-based survey. The weighted krill density and biomass were estimated to be 0.20 g/m² and 18 thousand tons (CV=33.8%) applying S_v difference 3.96-5.91 dB and 0.92 g/m² and 83 thousand tonnes (CV=31.4%) applying S_v difference -3.0-13.8 dB in 2017, respectively. Krill density and biomass were significantly higher in 2016 than those in 2017.